[rescue] Sun Blade 100 Question - IDE

[Patrick Giagnocavo]

On Sat, May 11, 2002 at 12:32:29AM -0400, George Adkins wrote:
> On Friday 10 May 2002 11:32 pm, Patrick Giagnocavo wrote:
> > On Fri, May 10, 2002 at 06:13:06PM -0400, Kurt Huhn wrote:
> > > > Most systems have at least 2 IDE channels.  Put one drive on each
> > > > channel.
> > >
> > > Thpplt!  Even 1 SCSI bus can handle 6 drives.  So to keep from getting a
> > > performance hit, you have to limit yourself to 2 drives.  I know I sound
> > > like a jerk, but I really think that's crap.
> >
> > Remember that IDE got its start from about 1989 and was designed to be
> > low cost.  Desktop drives of that era were stuffing maybe 200KB/second
> > through the channel.
> >
> This is no excuse for the apalling lack of foresight and piss-poor 
> engineering.  it's right in there with "Who'll ever need more than 640K..."

You gotta be careful when you say those kind of things while defending
SCSI.

What about the way you can blow up stuff by mis-matching HVD and SE
SCSI?  Why did they keep the same connector - they could have
easily keyed it somehow, or put in a small CPLD to figure out if
something wasn't right and avoid damage.

What about the original 8-bit SCSI spec?  What about drive size
limitations?  Go ahead, plug in an earlier SCSI device to your U160
device chain and watch performance go down...

In theory, SCSI is backwards compatible, but the price to convert
between the various interfaces via cabling or tailgates often does not
make sense from a cost standpoint.

IDE at least will never blow up stuff, is completely backwards
compatible (aside from a few drive issues when putting an old Conner
and old Seagate on the same channel), and the connector hasn't changed.

Connectors for SCSI include:

50-pin centronics
25-pin "Apple SCSI"
50-pin micro-D
68-pin 
80-pin SCA

I am not flaming you, just pointing out some stuff that shows that
SCSI isn't perfect either.  And many early SCSI devices are not
exactly compliant.

Let's just say that current SCSI has advantages for multiple drives,
for hot-swap (in terms of implementations, it is easier to find
hotswap SCSI than hotswap IDE) and for some other stuff.

Let's say that IDE has advantages in terms of price/performance and
generally higher storage capacity (higher capacities come out first in
IDE format due to SCSI user's emphasis/preference for IOPs).

./patrick