[conspire] Advice on Building a Computer

Mark Weisler mark at weisler-saratoga-ca.us
Mon Dec 31 13:56:44 PST 2007

On Monday 31 December 2007 11:29:00 Rick Moen wrote:
> Quoting Adrien Lamothe (a_lamothe at yahoo.com):
> (I guess, quoting Mark Weisler?):
> >> Well, I found a source for some new 68pin LVD SCSI drives, new...
> >> 73GB SCSI Seagate LVD 10KRPM U320 4MB 68pin ST373307LW
> >> for $123 each. Also some Cheetah's for $200 each. So, I'll proceed
> >> with the SCSI plan.
> >
> > You may want to check those drives, to insure they will configure
> > properly. Rick told me an interesting story about some aftermarket
> > SCSI drives, new ones, that were intentionally crippled by the
> > original system manufacturer so as to be not as configurable. They
> > were perfectly good drives, but only if you used one of them per
> > computer (I think that was the limitation, may not remember it
> > correctly. Rick can correct me).
> Long ago, there was a cheap-computer-parts firm called NCA Computer
> Products, which had several stores in the Bay Area, including a smaller
> one on El Camino Real in Palo Alto and the main store on Lawrence
> Expressway, Sunnyvale, right near Central Expressway.  The latter did
> huge volumes of business, including on cheap hard drives.  They also had
> a returns line that snaked out into the parking lot.
> I bought an inexpensive IBM SCSI drive there, and found after some
> experimentation that it refused to function on any SCSI chain that
> attempted to operate in disconnect mode.  Disconnect mode is one of the
> prime advantages of SCSI:  The HBA issues instructions to the device
> electronics to carry out some operation, and then disconnects from it --
> allows it to carry out that instruction independently without
> babysitting through the end of the operation, so that the HBA can at the
> same time be issuing instructions to other devices.  The net result is
> that, in sharp contrast to a PATA (parallel IDE) chain, a SCSI chain's
> devices can all be reading/writing simultaneously (which is why a SCSI
> chain's theoretical bus throughput limit in some cases actually matters,
> while PATA's was always pretty much a joke, since individual devices
> were slow, and bandwidth draw was never additive under any
> circumstances).
> Anyhow, this particular SCSI drive didn't work with disconnected mode
> enabled, at all.
> I called IBM to open an RMA case, and was referred to Tandem Computer,
> since my drive turned out to have a Tandem-OEM serial number, and not a
> regular IBM one.  Essentially, Tandem had made a bulk deal for cheap
> drives from IBM for a model that had only that one hard drive on a SCSI
> channel, in which scenario disconnected operation wouldn't have mattered
> or been useful, so that support was omitted from the electronics.
> Tandem probably had overstock, sold it off cheaply, and that overage
> ended up resold even more cheaply to NCA Computer Products.
> I drove back down from S.F. to Sunnyvale, stood in the huge long line,
> and swapped the IBM under "store warranty" terms for some other HD.
> Anyhow, Mark, you could verify with the "source" what S/Ns the units
> have (to determine whether they're OEM models), or you can ask the
> vendor whether they're OEMed.  Or you can just take a tiny chance, since
> these are discontinued drives anyway and probably out of warranty -- and
> rely on "store warranty" remedies and such.
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I've found some 68pin LVD SCSI drives here:
and here:
http://www.compuvest.com/Description.jsp?iid=472668 (thanks Ken for the tip)
so the SCSI approach is still in the running.

Thanks for the tip on the OEM aspect.

And concerning the power supplies, I'm not finding ATXGES (or ATX-GES) power 
supplies from the name brands you all have recommended. I do find some new 
off-brand power supplies described as ATXGES that typically include a phrase 
like " ...you can remove the handy adapter cable and use this PSU on an ATX 
should your needs require."  Thus, I think these are just generic PSUs fitted 
with the ATXGES adapter cable that someone is marketing as ATXGES power 

I think I might be better off to get a quality PSU and then use an adapter 
than buy one of these off-brand units.

Mark Weisler 
"Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our 
people need it sorely on these accounts." ---Mark Twain---
PGP: 0x68E462B6  http://pgp.mit.edu:11371/
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