ISA bus throughput
trixter at oldskool.org
Tue Jan 31 17:30:50 CST 2006
mbbrutman-cctalk at brutman.com wrote:
> While discussing this beast, the topic of putting a CD-ROM on it came up. (I
> would never do such a thing except for giggles.)
I've successfully used my Sound Blaster Pro + 1X CDROM drive to play
Sherlock Holmes (a video title, no less) on a 12MHz 286, so it is
possible. 1X is, as I'm sure you remember, 150KB/s.
As for giggles, it's really useful. Most 286s don't have 650MB of
> Well, let's go throught some quick math. 6 million clock cycles per second is a
> lot, but when you consider that each transation on the bus takes 4 to 5 cycles,
> and instructions take 4 to 5 cycles (average) on a 80285, the throughput might
> not be so hot.
Don't forget memory timing. Different boards/manufacturers did
> When writing to a hard disk, would this machine have used a tight processor
> loop, or would it have used DMA? Under what circumstances would it use DMA to
> transfer data to a hard disk?
I believe the AT and later used tight processor loops as they beat the
speed of DMA but I could wrong.
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
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