peterka@scubed.UUCP (Dan Peterka) (05/07/86)
[eat me]
I have a question concerning hard disk interfaces which arose out of a
conversation about why AT's are faster than XT's. Specifically, what
makes the AT's hard disk so much faster (I guess-timate at least 10 times
faster) than an XT's disk? What are the limiting factors on XT's and
AT's in getting data off of the disk and into RAM?
We came up with a number of factors of which we were unable to give
relative weighting factors to:
a) The AT has a 16 bit data bus while the XT has an 8 bit bus.
b) Generic AT hard disks have access times roughly half those
of generic XT hard disks.
c) The ST506 interface transfers data for both AT's and XT's at
5 megabits/second.
d) The 80286 is faster than the 8088.
Questions we could not find information on were:
a) How fast is an AT physically capable of moving data from a
controller to RAM. - How fast is an XT?
b) The 5 Megabit tranfer rate is (I think) how fast data gets
off the disk and into the controller. How fast does this
data come of the controller for both the AT and XT?
c) How close to the maximum data transfer rate are the AT and
XT disk controllers? - Can AT's and XT's benefit from the
SCSI controllers which have 10 Megabit/second tranfer rates?
Is transfer rate important - or is it all washed out by
disk access times?
And finally, don't bus speeds have to be the same for AT's and XT's
in order for things like graphic cards (originally designed for XT's)
to work in an AT?
-- Dan Peterka
S-Cubed, PO Box 1620, La Jolla CA 92037
seismo!s3sun!peterka (<-- may not work)