From: John P. Looney (valen at domain redbrick.dcu.ie)
Date: Wed 12 May 1999 - 13:07:03 IST
On Mon, May 10, 1999 at 03:15:31PM +0100, Edwards, Benjamin () mentioned:
> It is not the Specks of SCSI vs. IDE (We are talking about UltraDMA here I
> assume) which are of most relevance it is the architecture. IDE is built
> into the motherboard and uses its resources, SCSI on the other hand is a
> encapsulated interface (i.e. it works independently or the motherboard).
> This means that if there is a lot of disk I/O going through your system and
> you are using IDE the overall performance of the box will suffer a lot more
> than with SCSI.
Whao. That's nothing do with it. The IDE <-> PCI and SCSI <-> PCI bridges
can be on the motherboard, or in a card. Same performance. If you put an
AGP video chipset onto the motherboard, instead of onto an AGP card, there
is no performance increase.
The main difference is that the SCSI protocol allows the devices and the
interfaces chips to be a lot smarter than the ATAPI protocol does. Smarter
usually means more expensive. The Sun Ultra5s have an IDE CDROM drive.
Stick a CD in, and watch the machine crawl. My machine here has an IDE CD
Writer. Burning a CD at dual speed takes up loads of my CPU. IDE is cheap
> The other thing to consider is the speck of the disks.
> Just because you are using a superior interface douse not mean that the
> drive hardware is fully utilising it. For example there was a time when IBM
> (standard DMA) drives were faster than some ultraDMA drives as IBM had fully
> utilised the band-width from DMA and the others were just shoving UltraDMA
> interfaces in as a marketing thing.
UltraDMA - 33 MB/sec. And guess how many hard disk platters on the market
can deliver evening 8MB/sec ? Bugger all.
> The thing to look for as far as disk performance is concerned is spin speed.
> The problem with looking at data transfer rates is that it is specified is
> various different ways so it is often difficult to make a comparison.
Indeed. Spin speed is the most important factor for considering speed,
heat and cost. 7200RPM drives are damn fast. 10000RPM drives are just plain
silly expensive. 5400RPM are your usual ones, and to be honest, the best
value for money. If you want fast, stick in more memory & hope you can
buffer it. Memory is a thousand times faster than disk, so you win a lot
more on having more RAM than disk. If your system swaps, it means parts of
your programs are running a thousand times slower than they should.
> Lastly as SCSI is more isolated from the motherboard it is more stable.
Have you got worms ? That's got nothing to do with it. It could be
accurate to say that "SCSI cards are generally less buggy doing DMA than
IDE", but that's about it. If you notice, there is a single IDE driver in
the Linux kernel, that has to deal with IDE chipsets by dozens of vendors.
Usually SCSI drivers are fairly chip-specific.
-- Is PIRACY killing the Amiga?" bravely ponders AMIGA FORMAT - well, either that or someone's stopped manufacturing the hardware. -- www.ntk.net (30.04.99)
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