Path: utzoo!mnetor!uunet!husc6!bloom-beacon!spdcc!eli
From: eli@spdcc.COM (Steve Elias)
Newsgroups: comp.sys.ibm.pc
Subject: progs faster at 4.77 than 10...  (dma?)
Message-ID: <1063@spdcc.COM>
Date: 9 May 88 00:38:18 GMT
References: <23988@ucbvax.BERKELEY.EDU>
Reply-To: eli@spdcc.COM (Steve Elias)
Organization: yes
Lines: 13


the program described did lots of disk IO...

disk IO on an xt always goes through the DMA controller.
when your clone speed is increased from 4.77 to 10 MHz -- the clock
for the DMA chip may not be increased by the 10/4.77 ratio.

if the DMA clock has to be divided by some factor -- it may actually
run slower at 10 mhz than 4.77.  this obviously wouldn't be a great
design -- it may not be your problem...

a related note:  the dma chip on a stock 6 Mhz AT runs slower than the
chip on a 4.77 Mhz xt.  the AT doesn't use DMA for disk IO, though...