8 Jul
2006
8 Jul
'06
1:22 a.m.
Had a bit of a breakthrough on the quest to inexpensively get storage on the '4200 -
if you take apart the HSD05 SBB and pull off the white
sticker on the PCB there are solder pads for a 50-pin header on the DSSI bus side -
whoopee! After disassembling the PCB from a dead hard
drive (soaking them in an oven set at 375 is a great way to remove parts, but a bit
smelly. For SMDs you can shake or scrape them off, a pair
of pliers takes care of reluctant through-hole components) for the SCSI header, I soldered
it in place. Now for a trip to the electronics store for a
DIN-96 and a IDC 50-pin pin header (I'm going to wire up a SCSI cable with a F on one
end to plug into the backplane, a F for the HSD, and a M to
plug the bulkhead cable into). Now all I need to do is figure out power, mounting, and
SCSI signal issues.
For power, does anyone know about how much one ISE sled can source? I have one sled
mounting the TK70, so I can wire up a multitap feed from there
as long as it doesn't overload the sled. I don't think that the HSD, TK70 and one
or two 3.5" drives will overload a sled that can support a 5.25" full height
drive, but I'm not positive there yet.
The easiest way to do SCSI would be to have a direct ribbon cable from the HSD to the
drives. The slickest would be to feed it into the backplane as per
the official instructions. If I did that, I'd have to pull the SCSI signals back off
at the TK70 sled (it connects to the backplane SCSI instead of DSSI) and do a cable
anyway,
so at this point I'm thinking that the realism is not strictly necessary (only have
the one sled). Everything is reverseable, the HSD could even go back in its
SBB if necessary.
Mounting is the last issue - for the drives I think I'll use metal sheet stock with a
few holes drilled in it. Undecided for the board. DEC did a BA400 integrated HSD05
that sat in the QBUS bay and pulled power from the bus. The qbus-supplied power is not
hacker-friendly, and i'm not sure what to use as a support (would probably
use perfboard or acrylic, toyed with using stripped old PCBs). For convienience, I think
I'll probably wind up mounting the HSD on the back side of one of the homebrew
drive sleds.
If it works (and is photogenic), I'll take pictures. Definitely more attainable than
the $500 CMD SCSI cards.