Mailinglist Archive: opensuse (3637 mails)

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Re: [SLE] Info re supported hardware
  • From: Dave Smith <Dave.Smith@xxxxxx>
  • Date: Mon, 7 May 2001 14:48:44 +0100
  • Message-id: <20010507144844.W22572@xxxxxxxxxxxxxx>
On Sun, May 06, 2001 at 08:15:31PM -0400, abrahams@xxxxxxx wrote:
> Philipp Thomas wrote:
>
> > * Paul Abrahams [Sun, 06 May 2001 10:20:38 -0400]:
> >
> > >My hard drive claims to be ATA100; the motherboard claims UDMA 33/66 IDE. I'll
> > >admit that I know nothing of the relationship between ATA and UDMA, but I had
> > >assumed that the numbers were comparable, especially since most hard drives seem
> > >to be ATA66. Can you enlighten me?
> >
> > Yes, they're used interchangeably. BTW, what hard drive is it exactly?
> > But just try to run 'hdparm -tT /dev/<your disk>' (and please post the
> > output :). If you get Numbers below 66 MB/sec (and *no* currently
> > available hard disk even comes near that), it won't get any faster when
> > connected to a ATA100 controller.
>
> Well, there are two numbers, one above 66MB/sec and one below:
>
> root@suillus:/aux/home/pwa > hdparm -tT /dev/hda
>
> /dev/hda:
> Timing buffer-cache reads: 128 MB in 1.10 seconds =116.36 MB/sec

You won't improve much on this. Normal PCI is 32-bit, 33 MHz. As they
say, 'you do the maths'.

Unless things have moved on and we actually have 66 MHz PCI machines
around? Does anyone know about this? Of course, the moment you plug
in a 33 MHz card, the whole bus will slow down to 33 MHz anyway, so
even if there are 66 MHz machines around, they'll probably be slowed
down by one or more of the cards plugged in to them.

> Timing buffered disk reads: 64 MB in 2.03 seconds = 31.53 MB/sec

Limited by the physical disk itself; again, you won't improve on this
much. You'll get a slightly lower latency because the data can come
down the 100 MHz ATA bus faster, but compared to the latency of the drive,
the bus latency is peanuts.

>
> I'll see what happens when I attach the controller.
>
> > So if you've bought the controller for higher speed, you've wasted your
> > money. But at least you've now got two more ATA channels, so you can run
> > four ATA devices as master on their own channel. Running ATA devices as
> > master on their own channel is always the best way to attach them as
> > that will give you the most speed when talking to them in parallel (like
> > installing from CD) and will avoid trouble.
>
> That's good to know.
>
> Paul
>
>
>
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