Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!purdue!bu-cs!mirror!necntc!necis!spencer
From: spencer@necis.UUCP (John Spencer)
Newsgroups: comp.unix.i386
Subject: Re: Mylex SCSI Controller, 16550A UARTS
Message-ID: <1151@necis.UUCP>
Date: 12 Oct 89 13:57:12 GMT
References: <111016@nstar.UUCP> <707@fiver.UUCP> <2834NU013809@NDSUVM1> <22709@cup.portal.com> <765@crdos1.crd.ge.COM> <6075@tekgvs.LABS.TEK.COM> <16173@vail.ICO.ISC.COM>
Reply-To: spencer@necis.UUCP (John Spencer)
Organization: NEC Information Systems, Boxborough, MA
Lines: 9

In article <16173@vail.ICO.ISC.COM> dougp@ico.ISC.COM (Doug Pintar) writes:

>The real problem with disk transfer on AT-bus (and MCA as well, for that
>crowd) is NOT bus bandwidth but lousy controller design.  PIO controllers
>are cycle hogs, and most DMA controllers DON'T SUPPORT SCATTER/GATHER!  This
>makes transfers to/from physically-discontiguous memory pages very inefficient.
Could someone tell me where I can get more information on understanding PIO
controllers -vs- DMA controllers supporting and not supporting scatter/gather.
Any information would be extremely helpful.