On Mon, Mar 27, 2000 at 09:40:07AM +0200, Thomas Michael Wanka wrote:
> Hi,
> 
> that statement needs to be cleared! It depends upon what one wants 
> to do with the computer. As ide drives still need the processing 
> power of the CPU to do transferrs there are many environments 
> where SCSI is still more performant. Looking at these reviews will 
> show, that ide disks have equal or higher ransferrates than SCSI 
> disks, but most reviews do not consider CPU utilisation. From what I 
> know ide drives do not come close to scsi drives for latency. 
> 
> So a general rule was that when the pc has a high CPU utilisation 
> ide drives just dont get it. For the typical office environment ide 
> hardware was just fine.

No, this is not true. Ultra/33 DMA disks (with Ultra/33 controllers) use
DMA for data transfers, and don't need CPU work, just like SCSI.
Now there is the command setup and end; for this IDE beats SCSI:
just a few registers write for starting the command. IDE latency is much
better than SCSI (SCSI command startup has more overhead), and depending on
your SCSI board the IRQ load may be much higther (need to deal with
disconnect/reselect messages, etc ....).

Now all this is true only if you have one drive per channel. If you want
more drives SCSI is better :)

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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