Date: Wed, 22 Mar 95 13:17:17 MET From: sos@login.dknet.dk (S|ren Schmidt) To: phk@ref.tfs.com (Poul-Henning Kamp) Cc: hasty@star-gate.com, hackers@FreeBSD.org, faq@FreeBSD.org Subject: Re: Why IDE is bad Message-ID: <9503221217.AA08636@login.dknet.dk> In-Reply-To: <199503220912.BAA04694@ref.tfs.com>; from "Poul-Henning Kamp" at Mar 22, 95 1:12 am
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>
> I don't think you will find many ide's faster than the WDC, I know
> it can run faster on a better IDE-controller, but this is a fairly
> standard IDE controller so it's a good indication.
> And yes, but FreeBSD doesn't support DMA in IDE (yet ?)...
Was that my que word ??
DMA does not pay on E-IDE devices, it's not busmaster DMA, it
is the motherboards DMA we are talking about here.
This is very slow on standard MB's, but faster on PCI
(if they implemented it right).
However a "generic" driver would have to fall back to
the std. PC DMA and that is slower than using polled mode.
And besides only few drives support it anyway, and the high
rates of the PIO modes looks better in advertizing.
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.
And here is the catch, in that most el cheapo IDE drives has
inferior drive mechanics (hey they are cheap), and then some
fancy cache/interface electronics to make up for outdated
hardware....
>
I personally think that E_IDE and friends are the cleverest
sales trick in todays PC hardware.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Soren Schmidt (sos@FreeBSD.org | sos@login.dknet.dk) FreeBSD Core Team
So much code to hack -- so little time
..
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