keenmaster486 wrote on 2025-03-31, 20:28:

Well, I'm talking "bottleneck" in terms of "upgrading won't gain you any performance", which is the effect of the advice people tend to give about 286 video cards - "don't bother with the fast ones, the 286 isn't worth it!" - but what I'm finding is you can gain significant performance benefits anyway, even though it's a 286.

keenmaster486 wrote on 2025-04-01, 21:44:

that you shouldn't knock putting a faster VGA card in your 286 just because "it's a 286, it's already pushing pixels as fast as it can" or something like that.

All I'm reading here is a clear case of regurgitating (and responding to) old biases towards 286s that people still believe is gospel for some reason.

My favourite one is that Windows is slow on a 286 - which is weird, because I find Windows 3.0a to be relatively fast and responsive on a Turbo XT.

My favourite one is that Windows is slow on a 286 - which is weird, because I find Windows 3.0a to be relatively fast and responsive on a Turbo XT.

It's just a theory, but I think it had to do with how existing PC/XTs had been upgraded.
The simplest/cheapest upgrade was a motherboard swap. IBM 5160 style motherboard out, new no-name 80286 board in.
That would also explain horrible performance reports of the time.
If 8-Bit cards were kept, if old MFM/RLL fixed-disk drives remained set at bad interleave factor..
Then the 286 was essentially being turned into an 8086/V30 machine.
The RAM was being stuck at 1MB at best, too, of course.

Edit: What also comes to mind: RAM speed, waistates and 8-Bit bus speed.
It could have been that Turbo XTs had fast RAM, zero waistates and a higher clocked bus speed - which affected ordinary 8-Bit cards.

On an AT motherboard, the situation might have been different.
System had used waitstates and 8-Bit slots locked at 4,77 MHz for compatibility reasons.
Thus, it was slower than a native 8-Bit platform, such as an Turbo XT at 8 or ~10 MHz.

Also, Turbo XT owners maybe had changed interleave factor of their HDD.
Especially if the system was freshly assembled or if no HDD was in the system before the upgrade.

keenmaster486 wrote on 2025-03-31, 18:57:

Just an anecdotal experience. […]
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Just an anecdotal experience.

Had a WD90C00 card in my 286-12. Was getting benchmark speeds of ~1800 char/sec in Landmark, ~430us in Topbench. Noticeable slowdowns in Commander Keen when drawing lots of animated tiles, sprites, etc.

Replaced it with a WD90C30. Now Landmark says ~2800 char/sec (noticeably zippier character fills on startup), and Topbench says ~330us. Keen noticeably much faster, difficult to get enough changing stuff on screen to slow it down.

I have always heard that a 286 will bottleneck a very fast ISA video card. WD90C30 is on the top tier, fastest ISA VGA cards you can get, in the same league as ET4000. WD90C00 is among the slowest. So that gives you a little idea of what a 286 can do.

My bus speed is 6 MHz btw. The only two options in the BIOS are to match the CPU clock or cut it in half, and the system did not run stable at 12 MHz bus, even with every wait state under the sun.

Yesterday I got from ebay a WD90c30 , tested with a 286-12MHZ
I got 2824 Chr /ms just like you in landmark (I have a GD5429 that gets a similar score)

Then i found a jumper and read that it enables 0 wait states so I tried it and got 3766 Chr /ms

When I have more time i'll download the wolf3d benchmark for a more real test.

MarmotaArmy wrote on Today, 13:22:

Then i found a jumper and read that it enables 0 wait states so I tried it and got 3766 Chr /ms

Ooh. Very interesting. I'm going to look for that jumper now.

when using WDC90C3x cards it is also important to populate the full 1mb of VRAM in order to get the max speed from them

keropi wrote on Today, 15:47:

when using WDC90C3x cards it is also important to populate the full 1mb of VRAM in order to get the max speed from them

Sadly the mems that i bought from Aliexpress don't work. I bought five and I'll have to swap them to try if I can make the full mb work, but for now it stays at 512k