🚀 go-pugleaf

In article <1990Jun26.200549.792@amd.com> phil@pepsi.amd.com (Phil Ngai) writes:
>I wouldn't be quite so strong about that. VRAMs are a lot more expensive
>than regular DRAMs, and since you can run 50 ns page mode cycles on
>ordinary DRAMs, you can easily get 20 Mhz * 32 = 640 million bits/sec
>or 80 million 8-bit pixels/sec out of 1 megabyte of memory (8 x 256K x 4).
>That's 1.3 million pixels/frame at 60 Hz.

Aren't you a little optimistic in saying that you can easily get a
bandwidth of 20 MHz * 32 out of regular DRAMs? You will have to write
to the chips too, which, in addition to making one cycle unavailable
for a read operation, also makes the next read 'out of page'.

The calculations should be made for the worst case, not the best case.
And even a realistic assumption of 1.3 million pixels per frame
doesn't give you a very big margin, if you want a display of say 1024
pixels across.

--
Johan Myreen
jem@cs.hut.fi