Amiga 4000 motherboard fastram modules

[alainneke]

Hi,

I can't seem to get a clear view regarding compatibility of RAM modules on the Amiga 4000 motherboard. Is the board compatible with 60ns EDO RAM modules? In terms of performance, which kind of modules would give best experience (using the motherboard RAM sockets, not an accelerator)?

Thanks,

Alain

[hooverphonique]

Basically, you need to use 1MB,2MB,4MB or 8MB modules. With 2MB or 8MB, you can only use two modules at a time (1 in every second slot).
Using larger modules may work, but since they will have some floating address lines, they could be unreliable without mobo changes.
You need to set a jumper to either 1/2MB or 4/8MB.
EDO doesn't make a difference, as Ramsey doesn't take advantage of this mode (they should work fine though).
You can increase performance a bit by using 60ns modules and changing the "skip" bit in a register in Ramsey (IIRC, you need to do this after each reboot), but it's not something people generally bother doing.

[alainneke]

Great, thanks for the explanation. The Ramsey "skip" bit - is this also set by utilities such as "SpeedRamsey"? I was able to get a moderate increate in read throughput by using this (13,8 MB/s -> 16,3 MB/s).

[hooverphonique]

Yes, SpeedRamsey is indeed twiddling the skip bit. That ~18% increase looks right; IIRC the skip feature reduces memory access time from 5 to 4 cycles (-20%).
I doubt you would see anywhere near 18% general system performance increase though