SC-40 update

Rich Alderson RichA at
Thu Apr 16 19:02:38 CDT 2015

From: Cory Smelosky
Sent: Wednesday, April 15, 2015 11:31 AM

> On Wed, 15 Apr 2015, Rich Alderson wrote:

>> Use the Tops-10 Monitor Calls Reference Manual vol. 2 from Bitsavers, to see
>> the layout of a DEC HOM block (in the tables portion of the manual).  Vol. 1
>> has a good discussion of going from [1,1] to a file in a directory, and the
>> HOM block contains a pointer to [1,1].

> Hmmm. [1,1] is the ...what's the term... UFD? that I can access files 
> from.

MFD (Master File Directory).  It's not quite the same internally as a User
File Directory.  Also found in the tables, come to think of it.

> I figured out what that was, it's an issue with the file being larger than 
> an actual rp06 disk image (truncating it, setting it to an rm05,

Umm, isn't an RM05 300MB vs. 200MB for an RP06 (real unformatted capacities)?

>> If you like, we can move the discussion to the SimH list (to include Tim
>> Litt) or alt.sys.pdp10 (to include lots of other folks).

> That would get a bit offtopic for SIMH as I'm using KLH10 for this (I've 
> only gotten the image to be happy with fmt=dbd9, unsure if SIMH can do the 
> same conversion but I will try shortly)

SimH only knows one disk format, the one that KLH10 calls "dlw8" (little-
endian, 1 word in 8 bytes).

> No responses on alt.sys.pdp10, perhaps you can wake some people up? ;)

I'll rattle the cage.

> Oh, a heads up: the SC-40s you have can all run the newer supervisor (1.08 
> instead of 1.01. I found mine passed all diags after I imaged the newer 
> drive...aside from the SC-40 Exerciser of course, that's still unhappy 
> with my SCSI bus.)

OK, thanks!


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at

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