Mailinglist Archive: opensuse (3637 mails)

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Re: [SLE] ATA 100 vs. UDMA 33/66
I believe Dave Smith is essentially correct about the issues. A person will
see a reasonable and noticable increase in HDD response time more with drives
that run at 7200rpms, combine this with a ATA/udma 66/100 drive and you will
notice a difference. However, if you have a standard or 5400 rpm drive with
ata/udma 66/100 then the increase in speed/performance will be minimal. The
real increase comes from the seek-time and speed of the drive - 7200 rpms is
the real ticket. Also the HDD buffers help because it will load/cache of
data that is ready to go when called (e.g 2 or 4 MB HDD buffer/cache is
better the 512KB - excuse my mixing of term "buffer" and "cache", can't
remember the exact term for this feature - i believe it's a buffer but not
sure).

Cheers, Curtis Rey

On Sunday 06 May 2001 13:14, Dave Smith wrote:
> On Sun, May 06, 2001 at 01:22:35PM -0400, abrahams@xxxxxxx wrote:
> > Curtis Rey wrote:
> > > Paul Abrahams wrote:
> > > > 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?
> > > >From my experience the differences between ATA and UDMA are a matter
> > > > of
> > >
> > > semantics. I do beleive that the marketing departments of the various
> > > HD makers use this term ad-hoc (though I have read that there is a
> > > difference from a technical standpoint) For example mobo makers refer
> > > to their IDE channels as UDMA and the HD makers will use both terms
> > > (ATA and UDMA).
> >
> > So am I likely to gain anything by hooking my ATA100 hard drive to an
> > ATA100 controller rather than hooking it directly to an UDMA 33/66 mobo?
>
> AFAIK, ATA (AT Attachment) refers to the basic protocol by which the
> controller talks to the disk, whereas UDMA (Ultra-DMA) refers to the
> ability of the drive/controller combination to transfer data directly from
> the disk to the processor memory. I believe that the numbers (33/66/100)
> refers to the speed of the controller-drive bus. Therefore, if your drive
> is (for example) marked as ATA100 with UDMA, then it is UDMA100 compatible
> (i.e. the numbers can be placed after ATA or UDMA, and they mean the same
> thing). I believe that the correct way to say it is to put the speed after
> 'ATA', and put the UDMA separately, but, as usual, PC manufacturers seem to
> use the terms interchangeably.
>
> Anyway, as for whether it'll be faster, your PCI bus is limited to 33 MHz,
> 32 bit, and ATA is 16-bits wide, so an ATA66 card can (theoretically)
> saturate the PCI bus. There will be a slight performance advantage from
> ATA100, as the drive will be able to get data to the card faster, so will
> be able to ensure that the controller card never runs out of data to put on
> the PCI bus, but I don't think that the performance increase will be as
> much as you might hope for.
>
> Basically, latency for new accesses is determined more by the seek time of
> the drive (even the whizzy fast ones), and for large accesses, the data
> transfer rate will be limited by the PCI bus. Going from ATA33 to ATA66
> will probably make a significant difference; from ATA66 to ATA100 won't.
>
> Sorry.
>
> Of course, I could be totally wrong...
>
> --
> David Smith Tel: +44 (0)1454 462380 (direct)
> STMicroelectronics Fax: +44 (0)1454 617910
> 1000 Aztec West TINA (ST only): (065) 2380
> Almondsbury Home: 01454 616963
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> BS32 4SQ Work Email: Dave.Smith@xxxxxx
> Home Email: David.Smith@xxxxxxxxxxxxxxxxxxxx

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