More on DEC Pro 380

From: <(>
Date: Wed Jul 28 09:37:57 1999

> Anyway do the MFM controllers in PROs have the same hard-coded drive model
>restrictions as their Qbus big brothers, like the RQDXn family?

On a PRO, the MFM hard drive is ID'd by the number of heads and
number of cylinders. If you look at, for example, DW.MAC on a RT-11
distribution kit, you'll find the table quite easily. You can add
your own devices to the table - just keep in mind that it has to
be in ascending order by heads, and then ascending order by

OK, the above is a bit of an oversimplification - if the drive in
question happens to be a RD50, the drive might be damaged by the
seek test that counts the number of cylinders. So RD50's
are identified by a bit in the status/init register, and not
by the seek test.

The PRO's MFM controller only allows 3 bits for the head ID and 10
bits for the cylinder ID, so you can only use drives up to 8
heads and 1024 cylinders (aka the RD53).

 Tim Shoppa                        Email:
 Trailing Edge Technology          WWW:
 7328 Bradley Blvd		   Voice: 301-767-5917
 Bethesda, MD, USA 20817           Fax:   301-767-5927
Received on Wed Jul 28 1999 - 09:37:57 BST

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