Looking forward to watching this when I get time tonight 😀 Keep up the good work! 😀

dacow wrote:

Looking forward to watching this when I get time tonight 😀 Keep up the good work! 😀

Thank you!

It ended up a bit long winded but would have taken me much longer to produce had I tested it all first and then shot the footage. So my recommendations / thoughts at the end are a little bit different.

This board / CPU / system is much better at simulating a 486 than a 386. At the lowest setting it perfectly simulates a fast and tuned 386DX 40 MHz, which is often too fast for old, speed sensitive games.

I have been doing some testing on my P5GX-M board recently. I run the system at 266 MHz (8x33) normally and get 103.6 fps in DOOM timedemo3.

Turning L1 off, I get DOOM = 18.0 fps.

Turning AISP on (Part of the Performance Control Register), I get DOOM = 16.9 fps
At this point, my Speedsys score is 25.2
Note that setting AISP=on normally decreases the DOOM score by 40% if you leave L1 enabled.

Setting the RAM to 3T and divide by 4, while turning off some other register features (which don't help much, if any, because L1=off), DOOM = 12.6 fps
At this point, Speedsys score is 18.36

Now, if I set the CPU speed to 150 MHz with all the above, DOOM = 8.7 fps
Speedsys = 13.31

There is only a one jumper difference between 8x and 5x, so you can use the turbo button for this mod. This gives you 166 MHz.
To get to a 30 MHz FSB, there is also a one jumper difference, but your case needs to have an extra switch, or you can mount one to a slot cover. You'd need to use a single-pole, double-throw switch for this (which most turbo buttons are). Or you can be content with 166 MHz.

At 8.7 fps in DOOM, you are looking like a AMD 386DX-40. It would be interesting to see if increasing the I/O wait states can slow this down further if using an ISA graphics card, but at that point, it doesn't help much with getting back to Pentium speed levels.