I know this ground has been trod before, but here goes...

Can Non-DEC MFM drives be made to work with a RQDX3 controller by 
formatting with a Vaxstation 2000?

Definitely.  Last weekend I formatted a Seagate St-225 (RD31)
ST-251 (RD32), and a Maxtor XT2190 (RD54) that the previous owner
said had come out of a PC.  I also formatted a Mitsubishi MR535
(977,5,17->42 Mb), but it required some trials.  I needed to keep
cutting down the LBNs until all phases of the format worked.  My 
usable space when I brought it up on the MicroVax 3500 was 40 Mb.
(Now I'm sorry I threw away that 80 Mb MFM drive from my old PC.)

However, be forewarned: I also had three utter failures.  I subjected a 
perfectly good (worked with NetBSD!@) RD54 to this procedure, it went 
through the formatting stage just fine, and then ground noisly away 
in the "ChkPass" phase, until it woke the baby, and I had to halt.
I tried a second time the next day.  Same result (except the baby was on
a stroll.)  The other 2 failures were another ST-225 and ST-251 I had
astutely purchased on E-bay.  They also got to the ChkPass phase, 
issued several dots to the terminal, and then gave up.  

Now, of course, my RD54 no longer is usable.  At least not for the moment.
Now, my question is: If the Vaxstation 2000 thinks it knows the drive
parameters (i.e., RD54, RD31, RD32), it doesn't go through that
complicated dialog with you.  The bad part is, then you also have no
control over these parameters.  I had read somewhere that often the reason
for failing in the ChkPass phase was that the RBNsize (replacement
blocks) needed to be set
higher, if there were too many bad blocks.  And then you might need to
reduce the LBNsize (usable blocks), to make room for the RBNs.  Is 
it then possible to override the Vaxstation's suggested parameters for the
RD54, and drop down in that dialog and do it manually?

Of course this is no emergency.  I've a hoard of RD54s, and much larger
and more boring disks to play with.  But I particularly miss that one.

> [...]
> > Looking XT1140 up in my handy POCKET PCRef, I find that the 
> > CHS is (917,15,17), and the RD54 (XT2190) is (1224,15,17).
> > Formatted capacity 119 Mb, about a third of the way between an RD53 and
> > RD54.

For the person who asked, the POCKET PCRef is something you 
can find in many Electronics stores for about $10.  It has drive 
parameters for about 4000 drives, including the above.  It's blue, 
and fits in your pocket, if you wear loose clothing.


Doug



> 
> If a drive with CHS that doesn't match any normal DEC RDxx drive is
> formatted on a VAXstation 2000, will an RQDX3 deal with it properly?
> 
> I thought that the drive parameters were *required* to match the DEC
> drives.  It's my understanding that the RQDX3 does strange and wondrous
> things to figure out what kind of drives are attached.  Are there some
> on-disk structures describing the geometry which the controller will
> respect?
>