8 May
2007
8 May
'07
9:18 a.m.
On 8 May 2007 at 4:30, Jules Richardson wrote:
Some drives have speed control on one of the pins
(300/600 RPM, or 300/360
RPM), LED signal, motorised eject, disk change reset etc. - I suspect that it
doesn't hurt to have a few I/O lines set aside on the interface connector for
special cases.
One of the problems in engineering is knowing when to stop. DC37
connectors are not uncommon, exist in IDC versions (easy attachment).
50-pin D-subs are far less common. IDC headers aren't made for
frequent use and are subject to pin breakage and stress on the PCB.
Most of the signals you're talking about above are slow signals--
there's no particular need for those extra 5 pins that I mentioned to
be paired with a return, so you could have 5 additional programmable
pins (1 input, 4 outputs?) if needed. But the basic 32 lines I
specified will work with 95%+ of existing drives.
But please let's not run power over the cable--I've seen too many
toasted drives that resulted from someone getting something wrong.
Wouldn't you have to have motors running on four
drives at once, though? I'm
not sure that it matters in practice though as for an archival box I suppose
you only have one disk in one of the drives at any one time...
Before IBM came along, there were plenty of systems that ran the
5.25" drive motors at the same time. IBM gave up 2 drive selects
with their twist and got to use a feebler PSU on the 5150. Some DTC
hard disk/SCSI controllers gave back 4-drive operation by using an
"untwisted" cable. I don't see that as a problem.
Cheers,
Chuck