AST-AUTISMO wrote on 2020-09-11, 02:40:

- Will EDO modules work interchangeably with the existing FPM modules?

Perhaps, it depends on the timing of the OE signal. Avoid EDO if possible.

AST-AUTISMO wrote on 2020-09-11, 02:40:

- Will 50ns parts work interchangeably with the existing (i'm guessing) 60ns modules?

Very likely yes. If you have two banks that run interleaved on the same data lines (2 banks of 32bit each), you might get problems with very different RAM speeds, but as 50 and 60ns is not very different, and you still should have only one bank of 64 bits, with all data lines separate, I don't expect any problem.

AST-AUTISMO wrote on 2020-09-11, 02:40:

- Are there any other specifications to look for in terms of compatibility?

Yes! There are multiple variants on how 16-bit RAMs allow single-byte writes. The chip number you quoted is "DUAL CAS". There also are "DUAL WE" chips. Many graphics chip support both schemes (the BIOS has to choose which one to use), but you can't mix both schemes.

AST-AUTISMO wrote on 2020-09-11, 02:40:

- Are there any brands or specifications to avoid?

Not that I am aware of. It's best to get chips you can at least find a datasheet for, though.

AST-AUTISMO wrote on 2020-09-11, 02:40:

- What are the odds this upgrade will speed up the bad VBE performance?

Expanding the memory bus width can yield a great boost in performance. Use a video benchmark tool to find out whether video write performance actually is extremely low. On a PCI graphics card in a socket 7 system without write combining, I expect around 60MB/s for a decent graphics card.

mkarcher wrote on 2020-09-11, 05:54:

AST-AUTISMO wrote on 2020-09-11, 02:40:

- Are there any other specifications to look for in terms of compatibility?

Yes! There are multiple variants on how 16-bit RAMs allow single-byte writes. The chip number you quoted is "DUAL CAS". There also are "DUAL WE" chips. Many graphics chip support both schemes (the BIOS has to choose which one to use), but you can't mix both schemes.

Thank you for all this. I've found some Mosel chips that seem to fit.

Dual CAS like you pointed out, FPM and also appear to support both 50 and 60ns timings. From China, but I think I will roll the dice unless there is something I am missing.

Thanks again!

Quick update:

Found some chips on ebay:
9815F
v53c16256HK50

Installed and work great! (No performance increase in dos games though, which is a bummer... all slots full were supposed to double mem bandwidth)

Memory bandwidth is increased in Windows and the performance is increased by around 70% - depends on the resolution and colors used.

kixs wrote on 2020-11-13, 20:07:

Memory bandwidth is increased in Windows and the performance is increased by around 70% - depends on the resolution and colors used.

I suppose that may be true. I was hoping it would also be true in Dos games but since the ones I tried are 640x480 8-bit presumably memory bandwidth wasn't the limitation to begin with.