16mb SRAM Version 03 Board Success!

One board that's been frustrating me for a long time has been the Version 03 16mb SRAM board with the 80386 processor board

I built one of the earlier mezzanine based boards which worked well with 2mbx8 SRAM (Cypress CY62167ELL-45ZXI 45ns 5v), but was never able to get the V3 board to work properly with 4mbx8 SRAM (Alliance AS6C3216 55ns 3.3v). The errors were unpredictable, but most commonly resulted in 55H fill errors in the A00000-BFFFFF and E00000-FFFFFF range and almost random 1234H fill errors anywhere in memory. The errors weren't isolated to a single bank or SRAM and wait states / clock speed didn't seem to change much, although it was more stable at very low clock speeds.

After several months of intermittently trying things, I substituted 74F240 for U9 and 74F139 for U4. The board has run two full passes of the protected mode "J4" test without a single error.

Hopefully this might save someone else a bit of time.

- Gary