[comp.sys.dec] DEC Hard Drive Question

durham@w2xo.pgh.pa.us (Jim Durham) (03/30/91)

Does anyone know why an RQDX2 controller will not use
just any ST-506 interface drive, even if that drive is
physically identical (heads,cylinders,etc) to an RD53?
I know that an RD53 is a Micropolis 1325 and that you merely
change a jumper (R7) on the Micropolis to make the Digital
controller think it's OK (a real RD53). My question is, how
do you do this to a Maxtor 1085, which has the same head/cyllinder
layout? Anyone know this deep, dark secret?

-Jim  (durham@w2xo.pgh.pa.us)
 

terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.) (03/31/91)

In article <139@w2xo.pgh.pa.us>, durham@w2xo.pgh.pa.us (Jim Durham) writes:
> Does anyone know why an RQDX2 controller will not use
> just any ST-506 interface drive, even if that drive is
> physically identical (heads,cylinders,etc) to an RD53?
> I know that an RD53 is a Micropolis 1325 and that you merely
> change a jumper (R7) on the Micropolis to make the Digital
> controller think it's OK (a real RD53). My question is, how
> do you do this to a Maxtor 1085, which has the same head/cyllinder
> layout? Anyone know this deep, dark secret?

  Because the RQDX2 has to determine the drive type each time it is initial-
ized, it relies on the behavior of the drive when presented with various re-
quests, some legal and some not. You'd have to redo the firmware on the drive
to respond exactly as an R7-jumpered 1325 would, or re-do the firmware in the
RQDX2 to always assume an RQDX3.

  A better solution would be to use an RQDX3 controller, which writes the
geometry information on the drive itself. Thus, the RQDX3 formatter asks what
drive you have (if you respond "yes" to "Download UIT"). The RQDX3 can even
control drives with characteristics different from the supported DEC drives.
[Please don't write and ask how - it needs enough knowledge of MSCP layouts
that you'd figure it out yourself if you were up to it]

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381