Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!gatech!hubcap!ncrcae!ncrlnk!ncrwic!mlawless
From: mlawless@ncrwic.Wichita.NCR.COM (Mike Lawless)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Need info on 16-bit DMA for AT
Keywords: 8237-5, AT Bus
Message-ID: <4928@ncrwic.Wichita.NCR.COM>
Date: 14 Mar 89 18:04:21 GMT
References: <1901@randvax.UUCP> <37068@bbn.COM>
Reply-To: mlawless@ncrwic.UUCP (Mike Lawless)
Organization: NCR Corporation, Wichita, Kansas
Lines: 19

In article <37068@bbn.COM> tchu@BBN.COM (Tom Chu) writes:
>
>Unless you want to do things very slowly do not use DMA !! The DMA on the PC-
>is very slow. In fact the only device that I know of that uses DMA is the
>floppy controller. The DMA circuitry of the PC-AT is running at 5 MHZ (I thin
>but it has been awhile since I looked at a PC-AT). Hard disks on the PC-AT us
>MOVE strings, software to move data to and from the hard disk.

I have heard this before, but I wonder if this is true of all AT-class
machines, or just the ones from Big Blue and those that closely follow that
design.  For instance, is DMA performance any better on a typical 10-12 Mhz
At compatible machine using the Chips and Techologies chipset rather than
the antique Intel 8237?  Are there other proprietary DMA designs out there
that are faster?  Inquiring minds want to know.
-- 
Mike Lawless, NCR E&M Wichita, Box 20     (316) 636-8666   (NCR: 654-8666)
3718 N. Rock Road, Wichita, KS  67226     Mike.Lawless@Wichita.NCR.COM
{ece-csc,hubcap,gould,rtech}!ncrcae!ncrwic!Mike.Lawless
{sdcsvax,cbatt,dcdwest,nosc.ARPA}!ncr-sd!ncrwic!Mike.Lawless