* Mark Hahn (hahn@coffee.psychology.mcmaster.ca) [000419 18:31]:
> > > > and if you want to give it a try. As to my experience, SCSI stuff is
> > > > usually smoother, particularly in respect to CPU load.
> > >
> > > please don't repeat this trite old falshood. modern ATA controllers
> > > are just as busmastering as decent SCSI cards.
> >
> > So please name:
> > - ATA implementations that do tagged command queueing
>
> none. but TCQ has NOTHING to do with busmastering. under Linux,
> and all other nontrivial OSs, the kernel does head scheduling for IDE.
> this works extremely well, since linear address is monotonic with
> head position (ignoring bad-block remapping).
You're not referring to my previous two mails. I'm talking about
smoothness and CPU load. Smoothness means the system stays usable.
Imagine page faults during CD-ROM transactions, for example.
> > - ATA implementations that do dis-/reconnect in the same channel
>
> current IBM disks support this, and there's no controller support necessary.
> our driver doesn't support it yet either. again, it has nothing to do
> with busmastering, and indeed since you get 2 or 4 free ATA channels,
> and can add them for about $10 apiece, this is almost irrelevant.
I have a limited number of slots and am not going to fill all that junk
into my slots if I can do the same with only one SCSI adaptor.
> > To do busmastering, you also need a drive that actually offers this in
> > a decent manner.
>
> no, busmastering is a property of the controller. just as there exist
> plenty of non-busmastering SCSI controllers.
Name non-busmastering PCI SCSI controllers.
> > The Pioneer DR-A14S does not offer UDMA, just to name one.
>
> does it do any DMA mode? UDMA is much better, because it CRC's everything,
> but 16MB/s busmastering mode2 DMA is widely available and plenty fast for
> cdroms.
I don't currently have access to that drive. Still, with DMA, the
actual data transfer locks other devices in the same channel out.
During seeking, other devices are locked out.
This is not what I call "smooth".
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