nec v20

3 Articles

NEC V20 - Konstantin Lanzet, CC BY-SA 3.0 via Wikimedia Commons

Intel V. NEC : The Case Of The V20’s Microcode

November 7, 2023 by 18 Comments

Back in the last century, Intel saw itself faced with a need to have ‘second source’ suppliers of its 8088 and 8086 processors, which saw NEC being roped in to be one of those alternative suppliers to keep Intel’s customers happy with the μPD 8086 and μPD 8088 offerings. Yet rather than using the Intel provided design files, NEC reverse-engineered the Intel CPUs, which led to Intel suing NEC over copying the microcode that forms an integral part of the x86 architecture. In a recent The Chip Letter entry by [Babbage] this case is covered in detail.

Although this lawsuit was cleared up, and NEC licensed the microcode from Intel, this didn’t stop NEC from creating their 8086 and 8088 compatible CPUs in the form of the V30 and V20 respectively. Although these were pin- and ISA-compatible, the internal microcode was distinct from the Intel microcode due to the different internal microarchitecture. In addition the V20 and V30 also had a special 8080 mode, that provided partial compatibility with Z80 software.

Long story short, Intel sued NEC with accusations of copyright infringement of the microcode, which led to years of legal battle, which both set many precedents about what is copyrightable about microcode, and ultimately cleared NEC to keep selling the V20 and V30. Unfortunately by then the 1990s had already arrived, and sales of the NEC chips had not been brisk due to the legal issues while Intel’s new 80386 CPU had taken the market by storm. This left NEC’s x86-compatible CPUs legacy mostly in the form of legal precedents, instead of the technological achievements it had hoped for, and set the tone for the computer market of the 1990s.

Thanks to [Stephen Walters] for the tip.

An NEC V20 For Two Processors In One SBC

July 10, 2020 by 22 Comments

In the days when the best an impoverished student could hope to find in the way of computing was a cast-off 1980s PC clone, one upgrade was to fit an NEC V20 or V30 processor in place of the Intel 8088 or 8086. Whether it offered more than a marginal advantage is debatable, but it’s likely that one of the chip’s features would never have been used. These chips not only supported the 8086 instruction set, but also offered a compatibility mode with the older 8080 processor. It’s a feature that [Just4Fun] has taken advantage of, with V20-MBC, a single board computer that can run both CP/M-86 and CPM/80.

If this is starting to look a little familiar then it’s because we’ve featured a number of [Just4Fun]’s boards before. The Z80-MBC2 uses the same form factor, and like this V20 version, it has one of the larger ATMega chips taking place of the acres of 74 chips that would no doubt have performed all the glue logic tasks of the same machine had it been built in the early 1980s. There is a video of the board in action that we’ve placed below the break, showing CP/M in ’80, ’86, and even ’80 emulated in ’86 modes.

The only time a V20 has made it here before, it was in the much more conventional home of a home-made PC.

Continue reading “An NEC V20 For Two Processors In One SBC” →

Build Your Own PC — Really

April 14, 2017 by 37 Comments

There was a time when building your own computer meant a lot of soldering or wire wrapping. At some point, though, building a PC has come to mean buying a motherboard, a power supply, and just plugging a few wires together. There’s nothing wrong with that, but [Scott Baker] wanted to really build a PC. He put together an Xi 8088, a design from [Sergey] who has many interesting projects on his site. [Scott] did a great build log plus a video, which you can see below.

As the name implies, this isn’t a modern i7 powerhouse. It is a classic 8088 PC with a 16-bit backplane. On the plus side, almost everything is conventional through-hole parts, excepting an optional compact flash socket and part of the VGA card. [Scott] acquired the boards from the Retrobrew forum’s inventory of boards where forum users make PCBs available for projects like this.

Continue reading “Build Your Own PC — Really” →