i looked up a number of datasheets, trying to find out how long it takes for each vga card to perform a dram read/write, and come to such a conclusion, but not sure if i am reading the charts right:
2 clocks per read/write: cirrus5320 and later, et4000, oak087, s3 928/801/805, wd90c11 and later.
3 clocks: chips450 and 65530- 65545, trident8900cl/d and 9000. trident's 3-clock persisted till at least the 9420, 9440 has no detail, 9680 and later have 2-clock.
5 clocks: chips441, pvga1a/wd90c00, unimpressive, probably not going to be fast in svga modes.
7 clocks: oak037, chips451, cirrus51020, no wonder why they are slow.
8 clocks: chips452, intel82706.
unlisted cards are due to short of datasheets.