NEC V20 CPU: A bit of pep for an XT
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https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/...
(If not - zoom way in, and it's relatively readable.)
Works fine in Firefox on macOS 15 here.
https://en.wikipedia.org/wiki/NEC_V20#Variants_and_successor...
IIR, the V30 provided a notably better improvement (over the 8086), because the 16-bit memory bus meant it was less often starved for bandwidth.
I knew the V20 was a nice little upgrade for an XT, but had no clue people were actually running CP/M stuff on it too.
Would be pretty cool to see how that worked in real life. Old PC compatibility stuff was kinda nuts.
One very nice little win:
If you had an NEC chip, then Windows 3.0 ran in colour VGA mode. If you had an Intel chip, it wouldn't.
The VGA device driver was 286 code and the assumption was that VGA chips were only in 286 PCs.
(IBM's own 8086 and later very-low-end 80286 PS/2 machines, both called the Model 30, did not have VGA which was only in Microchannel machines; they had the inferior MCGA instead.)
If you had an 8088/8086 PC with VGA you couldn't run Win 3.0 in VGA mode. If you fit a V20 (instead of an 8088) or V30 (instead of an 8086), you could run Win 3.0 in colour VGA mode.
In 1990 this was the first mass-deployed 286-specific code a lot of people ever encountered: a device driver.
Lotus 1-2-3 r3 was 286-specific but it was niche; you could just stay on 1-2-3 r2 which worked fine on everything. Almost all other DOS apps were for 8088/8086.
The 80186 was so rare it wasn't even mentioned: the distinction was 8086 code or 80286 code. So this was a rare instance of Real Mode 286 code -- plain old unextended DOS 16-bit code, as opposed to Protected Mode code that needed an actual 80286 chip.
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