{"@context":["https://www.w3.org/ns/activitystreams",{"Hashtag":"as:Hashtag","sensitive":"as:sensitive","dcterms":"http://purl.org/dc/terms/","gts":"https://gotosocial.org/ns#","schema":"http://schema.org/","exifData":"schema:exifData","PropertyValue":"schema:PropertyValue","interactionPolicy":{"@id":"gts:interactionPolicy","@type":"@id"},"canQuote":{"@id":"gts:canQuote","@type":"@id"},"canReply":{"@id":"gts:canReply","@type":"@id"},"canLike":{"@id":"gts:canLike","@type":"@id"},"canAnnounce":{"@id":"gts:canAnnounce","@type":"@id"},"automaticApproval":{"@id":"gts:automaticApproval","@type":"@id"},"manualApproval":{"@id":"gts:manualApproval","@type":"@id"},"always":{"@id":"gts:always","@type":"@id"},"toot":"http://joinmastodon.org/ns#","blurhash":"toot:blurhash"}],"id":"https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/","type":"Article","attachment":[{"type":"Image","url":"https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2020/03/nec-v20-cpu.jpg?fit=720%2C409\u0026ssl=1","mediaType":"image/jpeg","name":"NEC V20"}],"attributedTo":"https://dfarq.homeip.net/author/admin/","content":"\u003Cp\u003EThe NEC V20 was an Intel 8088-compatible CPU that ran slightly faster. It was a niche CPU in the 1980s and 1990s but had a following as a cheap upgrade for power users, especially in instances where motherboard swaps were impractical. It\u0026#8217;s popular with retro computing enthusiasts today, as a \u003Ca href=\u0022https://dfarq.homeip.net/what-is-period-correctness/\u0022\u003Eperiod-correct\u003C/a\u003E upgrade. On September 22, 1986, NEC prevailed over Intel in court, clearing the way to sell it.\u003C/p\u003E\u003Cp\u003E\u003Cstrong\u003EThe NEC V20 was pin-compatible with the Intel 8088 but included some unique forward and backward compatibility features. It included the 80186 instruction set and could also emulate the Intel 8080, in addition to being faster than the 8088.\u003C/strong\u003E\u003C/p\u003E\u003Cp\u003E\u003C!--more--\u003E\u003C/p\u003E\u003Ch2\u003EThe NEC V20\u0026#8217;s slightly troubled past\u003C/h2\u003E\u003Cp\u003EIn 1982, NEC licensed the rights to produce the Intel 8088 as a second source. But in March 1984, NEC released the V20, an 8088 clone with some performance improvements. It had more than double the transistor count of the 8088 and could perform two data transfers concurrently, allowing it to complete more instructions in a given time than a real 8088.\u003C/p\u003E\u003Cp\u003EIntel sued in late 1984. NEC said the V20 was a cleanroom design. Ultimately NEC prevailed on September 22, 1986. The legal questions surrounding the V20 likely caused larger PC makers to shy away from it. By the time it was ruled legal, the market for XT-class machines was still healthy, but XTs were budget machines, so the lower transistor count of the 8088 meant a real 8088 was going to cost less in OEM quantities.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 as a cheap upgrade\u003C/h2\u003E\u003Cfigure\u003E\u003Ca href=\u0022https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/nec-v20-cpu/\u0022 rel=\u0022attachment wp-att-23246\u0022\u003E\u003Cimg src=\u0022https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2020/03/nec-v20-cpu.jpg?resize=300%2C170\u0026amp;ssl=1\u0022 alt=\u0022NEC V20\u0022 width=\u0022300\u0022 height=\u0022170\u0022 /\u003E\u003C/a\u003E\u003Cfigcaption\u003EAn NEC V20 is a cheap and easy upgrade for 8088 systems when you can\u0026#8217;t or don\u0026#8217;t want to swap a motherboard.\u003C/figcaption\u003E\u003C/figure\u003E\u003Cp\u003EThe \u003Ca href=\u0022http://www.ebay.com/sch/nec+(v20,D70108C)+(cpu,processor,microprocessor)\u0022\u003ENEC V20\u003C/a\u003E plugs directly into the Intel 8088 socket with no modifications necessary. It\u0026#8217;s slightly more efficient than an Intel 8088 running at the same clock speed. That means an NEC V20-upgraded machine performs anywhere from 8 to 30 percent faster than an 8088, depending on the application. For most applications, the improvement is around 20 percent. That\u0026#8217;s modest but may be enough to be noticeable. One place the V20 improves over the 8088 is performing multiplication and division in hardware, rather than in microcode. So it performs multiplication and division three times faster than an 8088.\u003C/p\u003E\u003Cp\u003EFor a much more technical deep dive, have a look at MartyPC\u0026#8217;s \u003Ca href=\u0022https://martypc.blogspot.com/2024/05/exploring-nec-v20-cpu.html\u0022\u003Ewriteup on the V20\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EWith Checkit 3.0, my Tandy 1000EX with an NEC V20 upgrade benchmarks 1.53x faster than the original PC/XT. In its stock configuration with a 7.16 MHz 8088, the 1000EX runs 1.31x faster than the original PC/XT.\u003C/p\u003E\u003Cp\u003EThe NEC V20 was a good processor upgrade option in machines that used nonstandard motherboards like the \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pcjr-and-tandy-1000/\u0022\u003ETandy 1000 and IBM PCjr\u003C/a\u003E, and inexpensive PC/XT clones like the \u003Ca href=\u0022https://dfarq.homeip.net/leading-edge-computers/\u0022\u003ELeading Edge Model D\u003C/a\u003E. In a genuine IBM PC/XT or other clone that followed the IBM design, swapping in a small-form-factor baby AT motherboard provided more performance. But a motherboard swap cost more too.\u003C/p\u003E\u003Cp\u003EToday, replacing the 8088 in an IBM PC or XT or compatible with a NEC V20 remains a popular upgrade option. It improves performance while permitting the owner to continue using the original motherboard. Plus it\u0026#8217;s a period correct upgrade involving a vintage part from 1984. And a fair number of people in the know made the swap back then. They\u0026#8217;re easy to find on \u003Ca href=\u0022http://www.ebay.com/sch/nec+(v20,D70108C)+(cpu,processor,microprocessor)\u0022\u003Eebay\u003C/a\u003E, with prices ranging from around $10-$25 (in US dollars) depending on the vintage of the chip and the locale. The lower the price, the greater the danger of a remarked chip.\u003C/p\u003E\u003Ch3\u003ENEC V20 variants\u003C/h3\u003E\u003Cp\u003EThe NEC V20 was available at speeds of 5 MHz, 8 MHz and 16 MHz. An 8 MHz version is suitable for upgrading PC and XT machines running at 4.77 or 7.16 MHz. The 16 MHz version is suitable for 9.54 MHz turbo XT clones.\u003C/p\u003E\u003Cp\u003EThe V20 carried a part number of D70108C, so you sometimes hear it referred to by that name. NEC had three licensees who also made the chip in the 1980s. So if you find a Sharp LH70108, Sony CXQ70108, or Zilog Z70108, they are all functionally the same chip.\u003C/p\u003E\u003Cp\u003EThe V20HL is a slightly later revision that runs cooler than the original.\u003C/p\u003E\u003Cp\u003EEven though I frequently see retro computer enthusiasts on Youtube putting heatsinks on their V20s, it\u0026#8217;s not really necessary. That\u0026#8217;s especially true of the later V20HL variant. The chips run cool anyway, and in PC applications they\u0026#8217;re always running at lower than their rated speed. The heatsink doesn\u0026#8217;t hurt anything, but it\u0026#8217;s overkill.\u003C/p\u003E\u003Ch3\u003EWhat\u0026#8217;s the point?\u003C/h3\u003E\u003Cp\u003EWhen you install an NEC V20 in an \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pc-introduced-august-12-1981/\u0022\u003EIBM PC 5150\u003C/a\u003E or \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pc-xt-model-5160/\u0022\u003EXT 5160\u003C/a\u003E, it\u0026#8217;s still an IBM. Although a faster motherboard will fit in an XT, it\u0026#8217;s not an IBM anymore once you do that. The V20 lets you retain the original motherboard and original BIOS, everything but the CPU, and it runs a little bit faster. And if you ever need to revert the mod, it\u0026#8217;s easy. It only takes a couple of minutes to swap the 8088 back into the CPU socket.\u003C/p\u003E\u003Cp\u003EIn a PCjr or Tandy 1000, the NEC V20 gives you a slightly faster CPU to complement the machine\u0026#8217;s enhanced graphics and sound. Some of Sierra\u0026#8217;s later titles run poorly on a stock 8088 and benefit from the boost. A \u003Ca href=\u0022https://dfarq.homeip.net/tandy-1000-models#tx\u0022\u003ETandy 1000 TX\u003C/a\u003E or TL with a 286 will give better performance. But that also means you have to find one. The 8088-based Tandy 1000s were more plentiful.\u003C/p\u003E\u003Cp\u003EThe other nice thing about a NEC V20 is that some network drivers that say they require a 286 will work on a V20. If you want to network your XT-class machine to make it easier to load software on it, this is helpful.\u003C/p\u003E\u003Cp\u003EAnd if your XT motherboard is able to use a third party BIOS like \u003Ca href=\u0022https://glabios.org/\u0022\u003EGLaBIOS\u003C/a\u003E, you can get a build optimized for the V20 that uses its extra instructions to improve overall system performance.\u003C/p\u003E\u003Ch3\u003ESpeeding up your XT IDE interface\u003C/h3\u003E\u003Cp\u003EIf you have an XT IDE interface and use a compact flash card with it, installing a V20 CPU and reassembling the XT IDE BIOS with V20/80186 instructions speeds up IDE access almost 90 percent. If you use a \u003Ca href=\u0022https://dfarq.homeip.net/tandy-3-in-1-expansion-review-for-the-1000hx-and-ex/\u0022\u003ETandy 3 in 1 card\u003C/a\u003E, Rob Krenicki has already built and provided a suitable \u003Ca href=\u0022https://github.com/rkrenicki/Tandy-EX-HX-3in1/tree/main/BIOS\u0022\u003EV20 optimized BIOS\u003C/a\u003E for that purpose. On my Tandy, disk throughput went from around 250K per second to around 500K per second.\u003C/p\u003E\u003Cp\u003ESo even if the benefits when running software can be inconsistent, an NEC V20 has a very noticeable impact on your loading times, at least if you use XT IDE. And everyone likes faster loading times.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 as an Intel 286 alternative\u003C/h2\u003E\u003Cp\u003EThe NEC V20 implements the Intel 80186 instruction set. The \u003Ca href=\u0022https://dfarq.homeip.net/intel-80186-cpu-so-misunderstood/\u0022\u003E186 saw limited use as a CPU in PC compatibles\u003C/a\u003E so it\u0026#8217;s an obscure chip in retro PC circles today. The later 286 and 386 processors proved far more popular and enduring. But since a fair bit of software that claims to require a 286 processor actually only uses 8086 and 186 instructions, the V20 has reasonable compatibility with the 286.\u003C/p\u003E\u003Cp\u003EThe V20 isn\u0026#8217;t as fast as a 286 partly because it\u0026#8217;s limited by the 8088\u0026#8217;s 8-bit data bus. A V20 running at 7.16 MHz benchmarks about half as fast as the original IBM PC/AT, which had a 6 MHz 286. But at least it allows some software to run that wouldn\u0026#8217;t run before.\u003C/p\u003E\u003Cp\u003EOne of those pieces of software happens to be the MS-DOS editor that shipped as part of Windows 95. The Windows 95 version of the DOS editor is smaller and faster than its DOS 6.22 counterpart because it doesn\u0026#8217;t rely on the QBASIC executable. It\u0026#8217;s also compiled with 80186 instructions, rather than the 8086 instructions the version that shipped with DOS 5 and DOS 6 used. So it won\u0026#8217;t run on an 8088, but runs happily on the NEC V20. And it\u0026#8217;s noticeably faster than the version from DOS 6.22. So you can make your V20-based DOS PC a little bit nicer to use by copying edit.exe from a Windows 95 PC to your DOS directory.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 in the 1980s and 1990s\u003C/h2\u003E\u003Cp\u003EThe big-name PC vendors like IBM and Tandy stuck with Intel 8088s and its \u003Ca href=\u0022https://dfarq.homeip.net/intel-8088s-and-non-intel-non-clones/\u0022\u003Eauthorized second-source providers\u003C/a\u003E like AMD and Siemens. However, by the late 1980s it wasn\u0026#8217;t hard to find XT clone boards with factory-installed V20 processors. These found their way into many white-box PC and XT clones. They provided an alternative for people who needed something faster than an 8088 but couldn\u0026#8217;t afford a 286, and \u003Ca href=\u0022https://dfarq.homeip.net/nec-v20-vs-intel-80186/\u0022\u003Ewanted good backward compatibility\u003C/a\u003E. And HP used the V20 in its \u003Ca href=\u0022https://dfarq.homeip.net/hp-200lx-and-related-palmtops/\u0022\u003EHP 95LX palmtop\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EPower users were aware of the V20, and I knew of a few people in the St. Louis area who took advantage of the V20\u0026#8217;s Intel 8080 compatibility mode to run \u003Ca href=\u0022https://dfarq.homeip.net/cpm-operating-system/\u0022\u003ECP/M\u003C/a\u003E software on their PC and XT clones.\u003C/p\u003E\u003Cp\u003EIt wasn\u0026#8217;t necessarily something you\u0026#8217;d find at just any computer store. It was more of a \u003Ca href=\u0022https://dfarq.homeip.net/remembering-computer-shopper/\u0022\u003Eback pages of Computer Shopper\u003C/a\u003E thing.\u003C/p\u003E\u003Ch2\u003ENEC V20 vs Intel 8088\u003C/h2\u003E\u003Cp\u003EWhen it comes to an NEC V20 vs Intel 8088, the chips have obvious similarities. But while there were lots of second-source 8088s, made with Intel\u0026#8217;s blessing, the V20 wasn\u0026#8217;t one of them. The V20 is more like the spiritual ancestor of \u003Ca href=\u0022https://dfarq.homeip.net/cyrix-processor-chips/\u0022\u003ECyrix 6\u0026#215;86 processors\u003C/a\u003E: independently reverse-engineered and pin-compatible with the dominant Intel processor of the time, with some more advanced technology bolted on. UMC was another company who tried NEC\u0026#8217;s approach, in the 486 era, but \u003Ca href=\u0022https://dfarq.homeip.net/umc-green-cpu-the-forbidden-486/\u0022\u003EUMC\u0026#8217;s 486 didn\u0026#8217;t survive Intel\u0026#8217;s challenges in court\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EThe 8088 wasn\u0026#8217;t the most efficient CPU of its era and NEC tried to address that, which is why a V20 is a bit faster than an 8088 when running at the same clock speed. The V20 gets about 20% more work done per clock cycle than its more famous competitor.\u003C/p\u003E\u003Cp\u003EThe V20 also ran at higher clock rates than the 8088, generally at 8, 10, and 16 MHz, but in PC applications it was generally clocked at 7.16 or 9.54 MHz. When you swap it in for an 8088, it runs at the same clock speed as the 8088 it replaced, with the performance increase coming strictly from its improved efficiency.\u003C/p\u003E\u003Cp\u003EThe V20 is still an XT-class CPU, like the 8088. But if you have an 8088-based system and want to put a little more spring in its step, the V20 is a reasonably priced upgrade to do so. It was affordable in the 1980s. And it\u0026#8217;s still readily available and affordable today.\u003C/p\u003E\u003Ch2\u003EThe PC-Sprint and the NEC V20\u003C/h2\u003E\u003Cp\u003EIn the mid 1980s, there was a hack going around called the \u003Ca href=\u0022https://ctrl-alt-rees.com/2020-03-02-overclocking-the-ibm-5150-8088-cpu-with-pc-sprint.html\u0022\u003EPC-Sprint\u003C/a\u003E. This was (and is) a free project that made a cheap accelerator for an IBM PC or XT. It also works in some of the more popular compatibles like the original \u003Ca href=\u0022https://dfarq.homeip.net/first-compaq-computer/\u0022\u003ECompaq Portable\u003C/a\u003E and the early Tandy 1000/1000A. In theory it might work with some other XT clone motherboards too. By adding the PC-Sprint daughterboard to a PC or XT and swapping the CPU, you can run a PC or XT at 7.16 MHz instead of 4.77 MHz. Some people call this the \u003Ca href=\u0022https://dfarq.homeip.net/history-of-overclocking/\u0022\u003Efirst overclocking project\u003C/a\u003E, but it\u0026#8217;s not really overclocking. You\u0026#8217;re swapping the CPU for one that runs at the rated speed, and the whole point of the mod is running the rest of the motherboard at 4.77 MHz.\u003C/p\u003E\u003Cp\u003EIn theory you probably \u003Cem\u003Ecould \u003C/em\u003Erun the stock 8088 at 7.16 MHz. And that would be overclocking. But it\u0026#8217;s also less reliable.\u003C/p\u003E\u003Cp\u003EThe PC-Sprint of course works fine with the V20. The V20 is designed to run at 8 or 16 MHz, so 7.16 MHz doesn\u0026#8217;t hurt it at all. A PC or XT running a V20 at 7.16 MHz will run noticeably faster than the original. It should give a 50-75% improvement. It still won\u0026#8217;t be as fast as a 6 MHz 286, but it will make a PC or XT more enjoyable to use, while retaining the soul of the old machine. 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class=\u0022shariff-text\u0022\u003Eemail\u003C/span\u003E\u0026nbsp;\u003C/a\u003E\u003C/li\u003E\u003Cli\u003E\u003Ca href=\u0022https://dfarq.homeip.net/feed/rss/\u0022 title=\u0022RSS feed\u0022 class=\u0022shariff-link\u0022\u003E\u003Cspan class=\u0022shariff-icon\u0022\u003E\u003C/span\u003E\u003Cspan class=\u0022shariff-text\u0022\u003ERSS feed\u003C/span\u003E\u0026nbsp;\u003C/a\u003E\u003C/li\u003E\u003C/ul\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cimg src=\u0022https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2017/06/dave_farquhar_181px.jpg?resize=100%2C100\u0026amp;ssl=1\u0022 width=\u0022100\u0022 height=\u0022100\u0022 alt=\u0022\u0022\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Ca href=\u0022https://dfarq.homeip.net/author/admin/\u0022 class=\u0022vcard author\u0022 rel=\u0022author\u0022\u003E\u003Cspan class=\u0022fn\u0022\u003EDave Farquhar\u003C/span\u003E\u003C/a\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cp\u003EDavid Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.\u003C/p\u003E\u003C/div\u003E\u003C/div\u003E\u003Cdiv\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Ca title=\u0022Mastodont\u0022 href=\u0022https://ioc.exchange/@siliconundergro\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003Ca title=\u0022Linkedin\u0022 href=\u0022https://www.linkedin.com/in/david-f-12656039/\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003Ca title=\u0022Pinterest\u0022 href=\u0022https://www.pinterest.com/davidf3612/\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003C/div\u003E\u003C/div\u003E\u003C/div\u003E","context":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/context","contentMap":{"en":"\u003Cp\u003EThe NEC V20 was an Intel 8088-compatible CPU that ran slightly faster. It was a niche CPU in the 1980s and 1990s but had a following as a cheap upgrade for power users, especially in instances where motherboard swaps were impractical. It\u0026#8217;s popular with retro computing enthusiasts today, as a \u003Ca href=\u0022https://dfarq.homeip.net/what-is-period-correctness/\u0022\u003Eperiod-correct\u003C/a\u003E upgrade. On September 22, 1986, NEC prevailed over Intel in court, clearing the way to sell it.\u003C/p\u003E\u003Cp\u003E\u003Cstrong\u003EThe NEC V20 was pin-compatible with the Intel 8088 but included some unique forward and backward compatibility features. It included the 80186 instruction set and could also emulate the Intel 8080, in addition to being faster than the 8088.\u003C/strong\u003E\u003C/p\u003E\u003Cp\u003E\u003C!--more--\u003E\u003C/p\u003E\u003Ch2\u003EThe NEC V20\u0026#8217;s slightly troubled past\u003C/h2\u003E\u003Cp\u003EIn 1982, NEC licensed the rights to produce the Intel 8088 as a second source. But in March 1984, NEC released the V20, an 8088 clone with some performance improvements. It had more than double the transistor count of the 8088 and could perform two data transfers concurrently, allowing it to complete more instructions in a given time than a real 8088.\u003C/p\u003E\u003Cp\u003EIntel sued in late 1984. NEC said the V20 was a cleanroom design. Ultimately NEC prevailed on September 22, 1986. The legal questions surrounding the V20 likely caused larger PC makers to shy away from it. By the time it was ruled legal, the market for XT-class machines was still healthy, but XTs were budget machines, so the lower transistor count of the 8088 meant a real 8088 was going to cost less in OEM quantities.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 as a cheap upgrade\u003C/h2\u003E\u003Cfigure\u003E\u003Ca href=\u0022https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/nec-v20-cpu/\u0022 rel=\u0022attachment wp-att-23246\u0022\u003E\u003Cimg src=\u0022https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2020/03/nec-v20-cpu.jpg?resize=300%2C170\u0026amp;ssl=1\u0022 alt=\u0022NEC V20\u0022 width=\u0022300\u0022 height=\u0022170\u0022 /\u003E\u003C/a\u003E\u003Cfigcaption\u003EAn NEC V20 is a cheap and easy upgrade for 8088 systems when you can\u0026#8217;t or don\u0026#8217;t want to swap a motherboard.\u003C/figcaption\u003E\u003C/figure\u003E\u003Cp\u003EThe \u003Ca href=\u0022http://www.ebay.com/sch/nec+(v20,D70108C)+(cpu,processor,microprocessor)\u0022\u003ENEC V20\u003C/a\u003E plugs directly into the Intel 8088 socket with no modifications necessary. It\u0026#8217;s slightly more efficient than an Intel 8088 running at the same clock speed. That means an NEC V20-upgraded machine performs anywhere from 8 to 30 percent faster than an 8088, depending on the application. For most applications, the improvement is around 20 percent. That\u0026#8217;s modest but may be enough to be noticeable. One place the V20 improves over the 8088 is performing multiplication and division in hardware, rather than in microcode. So it performs multiplication and division three times faster than an 8088.\u003C/p\u003E\u003Cp\u003EFor a much more technical deep dive, have a look at MartyPC\u0026#8217;s \u003Ca href=\u0022https://martypc.blogspot.com/2024/05/exploring-nec-v20-cpu.html\u0022\u003Ewriteup on the V20\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EWith Checkit 3.0, my Tandy 1000EX with an NEC V20 upgrade benchmarks 1.53x faster than the original PC/XT. In its stock configuration with a 7.16 MHz 8088, the 1000EX runs 1.31x faster than the original PC/XT.\u003C/p\u003E\u003Cp\u003EThe NEC V20 was a good processor upgrade option in machines that used nonstandard motherboards like the \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pcjr-and-tandy-1000/\u0022\u003ETandy 1000 and IBM PCjr\u003C/a\u003E, and inexpensive PC/XT clones like the \u003Ca href=\u0022https://dfarq.homeip.net/leading-edge-computers/\u0022\u003ELeading Edge Model D\u003C/a\u003E. In a genuine IBM PC/XT or other clone that followed the IBM design, swapping in a small-form-factor baby AT motherboard provided more performance. But a motherboard swap cost more too.\u003C/p\u003E\u003Cp\u003EToday, replacing the 8088 in an IBM PC or XT or compatible with a NEC V20 remains a popular upgrade option. It improves performance while permitting the owner to continue using the original motherboard. Plus it\u0026#8217;s a period correct upgrade involving a vintage part from 1984. And a fair number of people in the know made the swap back then. They\u0026#8217;re easy to find on \u003Ca href=\u0022http://www.ebay.com/sch/nec+(v20,D70108C)+(cpu,processor,microprocessor)\u0022\u003Eebay\u003C/a\u003E, with prices ranging from around $10-$25 (in US dollars) depending on the vintage of the chip and the locale. The lower the price, the greater the danger of a remarked chip.\u003C/p\u003E\u003Ch3\u003ENEC V20 variants\u003C/h3\u003E\u003Cp\u003EThe NEC V20 was available at speeds of 5 MHz, 8 MHz and 16 MHz. An 8 MHz version is suitable for upgrading PC and XT machines running at 4.77 or 7.16 MHz. The 16 MHz version is suitable for 9.54 MHz turbo XT clones.\u003C/p\u003E\u003Cp\u003EThe V20 carried a part number of D70108C, so you sometimes hear it referred to by that name. NEC had three licensees who also made the chip in the 1980s. So if you find a Sharp LH70108, Sony CXQ70108, or Zilog Z70108, they are all functionally the same chip.\u003C/p\u003E\u003Cp\u003EThe V20HL is a slightly later revision that runs cooler than the original.\u003C/p\u003E\u003Cp\u003EEven though I frequently see retro computer enthusiasts on Youtube putting heatsinks on their V20s, it\u0026#8217;s not really necessary. That\u0026#8217;s especially true of the later V20HL variant. The chips run cool anyway, and in PC applications they\u0026#8217;re always running at lower than their rated speed. The heatsink doesn\u0026#8217;t hurt anything, but it\u0026#8217;s overkill.\u003C/p\u003E\u003Ch3\u003EWhat\u0026#8217;s the point?\u003C/h3\u003E\u003Cp\u003EWhen you install an NEC V20 in an \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pc-introduced-august-12-1981/\u0022\u003EIBM PC 5150\u003C/a\u003E or \u003Ca href=\u0022https://dfarq.homeip.net/ibm-pc-xt-model-5160/\u0022\u003EXT 5160\u003C/a\u003E, it\u0026#8217;s still an IBM. Although a faster motherboard will fit in an XT, it\u0026#8217;s not an IBM anymore once you do that. The V20 lets you retain the original motherboard and original BIOS, everything but the CPU, and it runs a little bit faster. And if you ever need to revert the mod, it\u0026#8217;s easy. It only takes a couple of minutes to swap the 8088 back into the CPU socket.\u003C/p\u003E\u003Cp\u003EIn a PCjr or Tandy 1000, the NEC V20 gives you a slightly faster CPU to complement the machine\u0026#8217;s enhanced graphics and sound. Some of Sierra\u0026#8217;s later titles run poorly on a stock 8088 and benefit from the boost. A \u003Ca href=\u0022https://dfarq.homeip.net/tandy-1000-models#tx\u0022\u003ETandy 1000 TX\u003C/a\u003E or TL with a 286 will give better performance. But that also means you have to find one. The 8088-based Tandy 1000s were more plentiful.\u003C/p\u003E\u003Cp\u003EThe other nice thing about a NEC V20 is that some network drivers that say they require a 286 will work on a V20. If you want to network your XT-class machine to make it easier to load software on it, this is helpful.\u003C/p\u003E\u003Cp\u003EAnd if your XT motherboard is able to use a third party BIOS like \u003Ca href=\u0022https://glabios.org/\u0022\u003EGLaBIOS\u003C/a\u003E, you can get a build optimized for the V20 that uses its extra instructions to improve overall system performance.\u003C/p\u003E\u003Ch3\u003ESpeeding up your XT IDE interface\u003C/h3\u003E\u003Cp\u003EIf you have an XT IDE interface and use a compact flash card with it, installing a V20 CPU and reassembling the XT IDE BIOS with V20/80186 instructions speeds up IDE access almost 90 percent. If you use a \u003Ca href=\u0022https://dfarq.homeip.net/tandy-3-in-1-expansion-review-for-the-1000hx-and-ex/\u0022\u003ETandy 3 in 1 card\u003C/a\u003E, Rob Krenicki has already built and provided a suitable \u003Ca href=\u0022https://github.com/rkrenicki/Tandy-EX-HX-3in1/tree/main/BIOS\u0022\u003EV20 optimized BIOS\u003C/a\u003E for that purpose. On my Tandy, disk throughput went from around 250K per second to around 500K per second.\u003C/p\u003E\u003Cp\u003ESo even if the benefits when running software can be inconsistent, an NEC V20 has a very noticeable impact on your loading times, at least if you use XT IDE. And everyone likes faster loading times.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 as an Intel 286 alternative\u003C/h2\u003E\u003Cp\u003EThe NEC V20 implements the Intel 80186 instruction set. The \u003Ca href=\u0022https://dfarq.homeip.net/intel-80186-cpu-so-misunderstood/\u0022\u003E186 saw limited use as a CPU in PC compatibles\u003C/a\u003E so it\u0026#8217;s an obscure chip in retro PC circles today. The later 286 and 386 processors proved far more popular and enduring. But since a fair bit of software that claims to require a 286 processor actually only uses 8086 and 186 instructions, the V20 has reasonable compatibility with the 286.\u003C/p\u003E\u003Cp\u003EThe V20 isn\u0026#8217;t as fast as a 286 partly because it\u0026#8217;s limited by the 8088\u0026#8217;s 8-bit data bus. A V20 running at 7.16 MHz benchmarks about half as fast as the original IBM PC/AT, which had a 6 MHz 286. But at least it allows some software to run that wouldn\u0026#8217;t run before.\u003C/p\u003E\u003Cp\u003EOne of those pieces of software happens to be the MS-DOS editor that shipped as part of Windows 95. The Windows 95 version of the DOS editor is smaller and faster than its DOS 6.22 counterpart because it doesn\u0026#8217;t rely on the QBASIC executable. It\u0026#8217;s also compiled with 80186 instructions, rather than the 8086 instructions the version that shipped with DOS 5 and DOS 6 used. So it won\u0026#8217;t run on an 8088, but runs happily on the NEC V20. And it\u0026#8217;s noticeably faster than the version from DOS 6.22. So you can make your V20-based DOS PC a little bit nicer to use by copying edit.exe from a Windows 95 PC to your DOS directory.\u003C/p\u003E\u003Ch2\u003EThe NEC V20 in the 1980s and 1990s\u003C/h2\u003E\u003Cp\u003EThe big-name PC vendors like IBM and Tandy stuck with Intel 8088s and its \u003Ca href=\u0022https://dfarq.homeip.net/intel-8088s-and-non-intel-non-clones/\u0022\u003Eauthorized second-source providers\u003C/a\u003E like AMD and Siemens. However, by the late 1980s it wasn\u0026#8217;t hard to find XT clone boards with factory-installed V20 processors. These found their way into many white-box PC and XT clones. They provided an alternative for people who needed something faster than an 8088 but couldn\u0026#8217;t afford a 286, and \u003Ca href=\u0022https://dfarq.homeip.net/nec-v20-vs-intel-80186/\u0022\u003Ewanted good backward compatibility\u003C/a\u003E. And HP used the V20 in its \u003Ca href=\u0022https://dfarq.homeip.net/hp-200lx-and-related-palmtops/\u0022\u003EHP 95LX palmtop\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EPower users were aware of the V20, and I knew of a few people in the St. Louis area who took advantage of the V20\u0026#8217;s Intel 8080 compatibility mode to run \u003Ca href=\u0022https://dfarq.homeip.net/cpm-operating-system/\u0022\u003ECP/M\u003C/a\u003E software on their PC and XT clones.\u003C/p\u003E\u003Cp\u003EIt wasn\u0026#8217;t necessarily something you\u0026#8217;d find at just any computer store. It was more of a \u003Ca href=\u0022https://dfarq.homeip.net/remembering-computer-shopper/\u0022\u003Eback pages of Computer Shopper\u003C/a\u003E thing.\u003C/p\u003E\u003Ch2\u003ENEC V20 vs Intel 8088\u003C/h2\u003E\u003Cp\u003EWhen it comes to an NEC V20 vs Intel 8088, the chips have obvious similarities. But while there were lots of second-source 8088s, made with Intel\u0026#8217;s blessing, the V20 wasn\u0026#8217;t one of them. The V20 is more like the spiritual ancestor of \u003Ca href=\u0022https://dfarq.homeip.net/cyrix-processor-chips/\u0022\u003ECyrix 6\u0026#215;86 processors\u003C/a\u003E: independently reverse-engineered and pin-compatible with the dominant Intel processor of the time, with some more advanced technology bolted on. UMC was another company who tried NEC\u0026#8217;s approach, in the 486 era, but \u003Ca href=\u0022https://dfarq.homeip.net/umc-green-cpu-the-forbidden-486/\u0022\u003EUMC\u0026#8217;s 486 didn\u0026#8217;t survive Intel\u0026#8217;s challenges in court\u003C/a\u003E.\u003C/p\u003E\u003Cp\u003EThe 8088 wasn\u0026#8217;t the most efficient CPU of its era and NEC tried to address that, which is why a V20 is a bit faster than an 8088 when running at the same clock speed. The V20 gets about 20% more work done per clock cycle than its more famous competitor.\u003C/p\u003E\u003Cp\u003EThe V20 also ran at higher clock rates than the 8088, generally at 8, 10, and 16 MHz, but in PC applications it was generally clocked at 7.16 or 9.54 MHz. When you swap it in for an 8088, it runs at the same clock speed as the 8088 it replaced, with the performance increase coming strictly from its improved efficiency.\u003C/p\u003E\u003Cp\u003EThe V20 is still an XT-class CPU, like the 8088. But if you have an 8088-based system and want to put a little more spring in its step, the V20 is a reasonably priced upgrade to do so. It was affordable in the 1980s. And it\u0026#8217;s still readily available and affordable today.\u003C/p\u003E\u003Ch2\u003EThe PC-Sprint and the NEC V20\u003C/h2\u003E\u003Cp\u003EIn the mid 1980s, there was a hack going around called the \u003Ca href=\u0022https://ctrl-alt-rees.com/2020-03-02-overclocking-the-ibm-5150-8088-cpu-with-pc-sprint.html\u0022\u003EPC-Sprint\u003C/a\u003E. This was (and is) a free project that made a cheap accelerator for an IBM PC or XT. It also works in some of the more popular compatibles like the original \u003Ca href=\u0022https://dfarq.homeip.net/first-compaq-computer/\u0022\u003ECompaq Portable\u003C/a\u003E and the early Tandy 1000/1000A. In theory it might work with some other XT clone motherboards too. By adding the PC-Sprint daughterboard to a PC or XT and swapping the CPU, you can run a PC or XT at 7.16 MHz instead of 4.77 MHz. Some people call this the \u003Ca href=\u0022https://dfarq.homeip.net/history-of-overclocking/\u0022\u003Efirst overclocking project\u003C/a\u003E, but it\u0026#8217;s not really overclocking. You\u0026#8217;re swapping the CPU for one that runs at the rated speed, and the whole point of the mod is running the rest of the motherboard at 4.77 MHz.\u003C/p\u003E\u003Cp\u003EIn theory you probably \u003Cem\u003Ecould \u003C/em\u003Erun the stock 8088 at 7.16 MHz. And that would be overclocking. But it\u0026#8217;s also less reliable.\u003C/p\u003E\u003Cp\u003EThe PC-Sprint of course works fine with the V20. The V20 is designed to run at 8 or 16 MHz, so 7.16 MHz doesn\u0026#8217;t hurt it at all. A PC or XT running a V20 at 7.16 MHz will run noticeably faster than the original. It should give a 50-75% improvement. It still won\u0026#8217;t be as fast as a 6 MHz 286, but it will make a PC or XT more enjoyable to use, while retaining the soul of the old machine. 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class=\u0022shariff-text\u0022\u003Eemail\u003C/span\u003E\u0026nbsp;\u003C/a\u003E\u003C/li\u003E\u003Cli\u003E\u003Ca href=\u0022https://dfarq.homeip.net/feed/rss/\u0022 title=\u0022RSS feed\u0022 class=\u0022shariff-link\u0022\u003E\u003Cspan class=\u0022shariff-icon\u0022\u003E\u003C/span\u003E\u003Cspan class=\u0022shariff-text\u0022\u003ERSS feed\u003C/span\u003E\u0026nbsp;\u003C/a\u003E\u003C/li\u003E\u003C/ul\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cimg src=\u0022https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2017/06/dave_farquhar_181px.jpg?resize=100%2C100\u0026amp;ssl=1\u0022 width=\u0022100\u0022 height=\u0022100\u0022 alt=\u0022\u0022\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Ca href=\u0022https://dfarq.homeip.net/author/admin/\u0022 class=\u0022vcard author\u0022 rel=\u0022author\u0022\u003E\u003Cspan class=\u0022fn\u0022\u003EDave Farquhar\u003C/span\u003E\u003C/a\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Cdiv\u003E\u003Cp\u003EDavid Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.\u003C/p\u003E\u003C/div\u003E\u003C/div\u003E\u003Cdiv\u003E\u003C/div\u003E\u003Cdiv\u003E\u003Ca title=\u0022Mastodont\u0022 href=\u0022https://ioc.exchange/@siliconundergro\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003Ca title=\u0022Linkedin\u0022 href=\u0022https://www.linkedin.com/in/david-f-12656039/\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003Ca title=\u0022Pinterest\u0022 href=\u0022https://www.pinterest.com/davidf3612/\u0022 rel=\u0022nofollow noopener\u0022 class=\u0022saboxplugin-icon-grey\u0022\u003E\u003C/span\u003E\u003C/a\u003E\u003C/div\u003E\u003C/div\u003E\u003C/div\u003E"},"name":"NEC V20 CPU: A bit of pep for an XT","nameMap":{"en":"NEC V20 CPU: A bit of pep for an XT"},"icon":{"type":"Image","url":"https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2020/03/nec-v20-cpu.jpg?resize=55%2C55\u0026ssl=1","mediaType":"image/jpeg","name":"NEC V20"},"image":{"type":"Image","url":"https://i0.wp.com/dfarq.homeip.net/wp-content/uploads/2020/03/nec-v20-cpu.jpg?fit=720%2C409\u0026ssl=1","mediaType":"image/jpeg","name":"NEC V20"},"preview":{"type":"Note","content":"The NEC V20 was an Intel 8088-compatible CPU that ran slightly faster. It was a niche CPU in the 1980s and 1990s but had a following as a cheap upgrade for power users, especially in instances where motherboard swaps were impractical. It's popular with retro computing enthusiasts today, as a period-correct upgrade. On September 22, 1986, NEC prevailed over Intel in court, clearing the way to sell it.\n\nThe NEC V20 was pin-compatible with the Intel 8088 but included some unique forward and backward compatibility features. It included the 80186 instruction set and could also emulate the Intel 8080, in addition to being faster than the 8088. [\u2026]"},"published":"2026-09-21T11:00:09Z","summary":"The NEC V20 was an Intel 8088-compatible CPU that ran slightly faster. It was a niche CPU in the 1980s and 1990s but had a following as a cheap upgrade for power users, especially in instances where motherboard swaps were impractical. It's popular with retro computing enthusiasts today, as a period-correct upgrade. On September 22, 1986, NEC prevailed over Intel in court, clearing the way to sell it.\n\nThe NEC V20 was pin-compatible with the Intel 8088 but included some unique forward and backward compatibility features. It included the 80186 instruction set and could also emulate the Intel 8080, in addition to being faster than the 8088. [\u2026]","summaryMap":{"en":"The NEC V20 was an Intel 8088-compatible CPU that ran slightly faster. It was a niche CPU in the 1980s and 1990s but had a following as a cheap upgrade for power users, especially in instances where motherboard swaps were impractical. It's popular with retro computing enthusiasts today, as a period-correct upgrade. On September 22, 1986, NEC prevailed over Intel in court, clearing the way to sell it.\n\nThe NEC V20 was pin-compatible with the Intel 8088 but included some unique forward and backward compatibility features. It included the 80186 instruction set and could also emulate the Intel 8080, in addition to being faster than the 8088. [\u2026]"},"tag":[],"updated":"2026-09-21T11:02:01Z","url":"https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/","to":["https://www.w3.org/ns/activitystreams#Public"],"cc":["https://dfarq.homeip.net/wp-json/activitypub/1.0/actors/1/followers"],"mediaType":"text/html","replies":{"id":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/replies","type":"Collection","first":{"id":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/replies?page=1","type":"CollectionPage","partOf":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/replies","items":[]}},"likes":{"id":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/likes","type":"Collection","totalItems":0},"shares":{"id":"https://dfarq.homeip.net/wp-json/activitypub/1.0/posts/23245/shares","type":"Collection","totalItems":0},"interactionPolicy":{"canAnnounce":{"automaticApproval":"https://www.w3.org/ns/activitystreams#Public","always":"https://www.w3.org/ns/activitystreams#Public"},"canLike":{"automaticApproval":"https://www.w3.org/ns/activitystreams#Public","always":"https://www.w3.org/ns/activitystreams#Public"},"canQuote":{"automaticApproval":"https://www.w3.org/ns/activitystreams#Public","always":"https://www.w3.org/ns/activitystreams#Public"},"canReply":{"automaticApproval":"https://www.w3.org/ns/activitystreams#Public","always":"https://www.w3.org/ns/activitystreams#Public"}}}