Date: Thu, 23 Mar 1995 01:13:13 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, sos@login.dknet.dk Cc: faq@FreeBSD.org, hackers@FreeBSD.org, hasty@star-gate.com, phk@ref.tfs.com Subject: Re: Why IDE is bad Message-ID: <199503221513.BAA17998@godzilla.zeta.org.au>
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>> >And that is the main thing on E-IDE, the drives are designed >> >with enough onboard cache, that coretest etc. reports transfer >> >rates close to the interface speed (13MB sec or so), but the >> >drive cannot hold this speed when it has to read from the media. >> >> This is also good for reducing interrupt overhead. >Hmm, most of the drives would intterupt once each sector anyway >even when doing DMA, so there is really nothing gained... Interrupts don't take long (< 10 usec on a DX2/66) if the driver doesn't do anything. The IDE driver does a lot. It takes at least 155 usec to transfer 512 bytes at 3.3MB/sec. Dividing `a lot' by (11.3/3.3) has good effects. >> I expect better IDE drives would have been avaiable if the >> interface had supported them. >Actually I think not, the IDE thing is about making CHEAP disks >for the average PC user. It is much better advertising to have a >500MB drive than a 300MB drive, who cares about performance ??? "Only" half the posters in comp.sys.ibm.pc.hardware.*. Even the average user needs ever increasing performance to run the latest bloatware. Bruce
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