🚀 go-pugleaf

In article <13997002@zl2tnm.gen.nz>, don@zl2tnm.gen.nz (Don Stokes) writes:
> What's the R7 jumper?  (He asks naively.)

Turns out that it modifies the behavior of the drive on certain error
conditions.  The RQDXn controllers determine what kind of drive they're talking
to by asking the drive to do things that it can't (seek to non-existent
cylinders, read from non-existent heads, etc.) and looking at the resulting
drive status.  Installing R7 makes the RD53 /Micropolis 1325/1335 behave so
that the RQDXn can identify it as such. 

This bizarre technique is also the reason that "generic" drives with identical
geometries can't be sub'd for the DEC ST506 drives. 

(All of the above info is from Terry Kennedy.)

> I pulled out an RD53 that my VAXstation didn't want to talk to any more,
> set the unit select jumper and tossed it in a PC.  It formatted and it's
> been fine ever since.  Try putting R7 back in....  
> 
> Otherwise, is your power supply up to the task?  

Yes -- both supplies in question can run TWO 5-1/4 FH drives.  

> (Actually, doesn't R7 drop the amount of power pulled by these
> little guys on startup?)

I don't know -- maybe it does that too -- when dealing with stuff from the DEC
"proprietary hardware" era, just about anything is possible.  ("Digital has it
now, and we've made DAMNED certain that nobody else ever will!")

> Don Stokes, ZL2TNM (DS555)                        don@zl2tnm.gen.nz (home)
> Network Manager, Computing Services Centre            don@vuw.ac.nz (work)
> Victoria University of Wellington, New Zealand              +64-4-495-5052

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
drivers, internals, networks, applications, and training for VMS and Windows-NT
uucp 'g' protocol guru and release coordinator, VMSnet (DECUS uucp) W.G., and 
Chair, Programming and Internals Working Group, U.S. DECUS VMS Systems SIG 
Internet:  jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
Uucp:  ...{crash,eisner,uunet}!cmkrnl!jeh