DEC ST506 Interface Adapter Part No 54-17003-01

Pete Turnbull pete at
Sat May 16 10:05:08 CDT 2009

On 14/05/2009 22:51, Julian Skidmore wrote:
>> I thought it could only format "known" disk types, not arbitrary disks
>> (a firmware limitation in the formatter application, not a hardware
>> limitation). 
> Surely, it's possible to hack an RQDX3 controller's ROM to support arbitrary geometries? I have an old ST506 MFM drive hanging around here I keep toying with using. Does someone have a listing for the ROM?

The geometry information isn't in the controller ROM, it's in the 
formatter software.  In the PDP-11 version, it's in tables in the 
ZRQC??.BIN diagnostics program that runs under XXDP.  The tables have 
space for eight entries.  I don't know about the version in microVaxen, 
which may be in firmware.  The data isn't just drive geometry, though. 
There's lots of other formatting information in the tables, some of 
which is hard to work out, things like the encoded drive type, 
interleave factors, head-to-head skew, cylinder-to-cylinder skew, gap 
sizes, step times, replacement and cacheing control tables, location of 
spare tracks and blocks, location of disgnostics blocks, track and block 
groupings, that are written to the disk.  Something like 40 words per 
table, IIRC.  I worked most out 18 years ago for some Rodime disks but I 
can't find all the notes I made.

Pete						Peter Turnbull
						Network Manager
						University of York

More information about the cctalk mailing list