First post, by FesterBlatz
The title says it all! Following a vague post on k6plus.com regarding a simple modification to correct the "slowness" issue when paring K6-2/3 "plus" variants with Aladdin V rev G Northbridge equipped P5As (rev 1.05 & 1.06), I went ahead and tried this on my P5A rev 1.06 -- so far the results look promising!
The post I saw is here: http://www.k6plus.com/phpBB3/viewtopic.php?f=3&t=2340
To attempt this myself, all I did was use a 1K resistor to pull WB/WT# (pin AA5) up to Vcore 3.3v at VCC3 pin AJ19.
So far the only test I've done is run Quake 2 using 3DNow Software 800x600 mode with a K6-2+ @550MHz installed, and compare to my MVP3 based K6-3+ 550MHz machine with the exact same Quake settings, 98SE, identical video cards and driver version. I get 19.8 FPS on the modded P5A K6-2+ and 16.1 FPS on the MVP3 K6-3+. Considering the K6-3+ on the MVP3 board has double the on-die L2 cache, my P5A outperforming it even slightly seems to be a good indication that it isn't being hampered by the "slowness" hardware bug that effects rev 1.05 and newer boards.
I have no idea what the actual "bug" is, but this seems to indicate the ALi M1541 rev G Northbridge may not be asserting WB/WT# correctly--either poor timing or not at all. Somehow simply forcing that input high seems to work around the issue... I'm not sure if there are any side-effects yet, but so far the system seems perfectly stable.
Having just got back into SS7 since the 90s, I don't have a collection of benchmark utilities installed yet to perform a more detailed comparison. But considering Quake2 seems to play just fine the bug appears to be a non-issue now. Prior to the mod I was getting about half that frame-rate.
I'll continue to mess around with this and be sure to update with pictures and whatever benchmarks I can provide, so feel free to request.
Hopefully some folks find this useful!
UPDATE: Here's a picture of the mod. I used a SMD resistor but an axial resistor would work fine too. Just be careful not to accidentally bridge to any adjacent pins or vias. It's a little difficult to see in the picture, but I used Kapton tape to help prevent any shorts.