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NEC V20 CPU: A bit of pep for an XTdfarq.homeip.net

It's a drop in replacement, it's faster, and it's cheap. What's not to like?

11 points•jnord•10 days ago•11 comments•
#cpu#bit#nec#v20#pep#v20 cpu#nec v20#nec v20 cpu

11 comments

tom_10 days ago
I just got served a big chunk of JSON, not even pretty-printed, with the text in there... somewhere. Difficulty level: quite high, even in reader mode.

(same on macOS+Firefox and iPhone+Safari)

vlasky10 days ago
I think it's a caching issue. I got it to render properly by adding a cache-busting query string to the URL:

https://dfarq.homeip.net/nec-v20-cpu-a-bit-of-pep-for-an-xt/...

lproven9 days ago
> Difficulty level: quite high, even in reader mode.

Works fine in Firefox on macOS 15 here.

glimshe10 days ago
I thought it was an error message but I can't tell from my phone using Brave.
lproven9 days ago
General tip...

https://www.spacebar.news/stop-using-brave-browser/

bell-cot10 days ago
Appears to be fixed now.

(If not - zoom way in, and it's relatively readable.)

drcongo10 days ago
You're not alone.
bell-cot10 days ago
Not mentioned - the NEC V30 CPU, which was the V20's 8086-replacement near-twin:

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.

rbanffy10 days ago
I knew it was possible to run CP/M programs (and CP/M itself) on my PC with its V20, but I never found out how.
mr_big_bowls9 days ago
Honestly the CP/M part is what caught my attention.

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.

lproven9 days ago
It worked well. I used a few V20 and V30 PCs.

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.

Citations:

https://www.os2museum.com/wp/antique-display-driving/

https://www.vogons.org/viewtopic.php?t=53942

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