of all 2d cards, cirrus' datasheet seems to give most details on dram timing. in short, tpc seems to be the most critical parameter and equals to 2000/mclk, probably owing to 2cycle access.
as a result, 50mhz, 60mhz and 80mhz demands a tpc of 40ns, 33ns and 25ns respectively. and since edo dram has much lower tpc than regular dram, we can come to a simplified conclusion:
50mhz(5420~28) requires 60ns dram
60mhz(5429/30/34/40) requires 50ns dram
80mhz(5436/46) requires 60ns edo

i guess this applies to most other cards aswell, but the s3 968 and trio64 use single clock edo mode, does this mean that tpc must be halved as well?(20ns for 50mhz, 16ns for 60mhz)
if thats the case, s3 968 would require 50ns edo-vram, while trio64v2 would require 40ns edo.

also i wonder which of the following cards would have more actual bandwidth:
s3 968: 50mhz 64bit single clock vram, vram to ramdac is 128bit.
s3 trio64v2: 60mhz 64bit single clock edo.
cirrus5480: 100mhz 64bit sgram, which also appears to do single clock burst.
chips69030: 83mhz 64bit integrated sdram.
tseng et6100: approximately ~100mhz 64bit mdram, does it have dual port like vram anyway?