SC-40 update

Cory Smelosky b4 at
Wed Apr 15 13:31:22 CDT 2015

On Wed, 15 Apr 2015, Rich Alderson wrote:

> Cory,
> It may be that CI$ defined some bits differently in their monitor.  I strongly
> suggest that you examine the (emulated?) drive using FILDDT.  Start by locating
> the HOM block (which might not be where DEC would put it; I vaguely remember a
> difference between Stanford and Mike&Stewart vis-a-vis TOPS-20 file systems).
> You can that with

Could be, will look in a bit.

Could also be an error in (what a 
friend used to convert the 584-byte-sector drive to something usable in 

I can copy all files in the first 132 blocks (not counting any metadata 
blocks) fine.  That's HOM.SYS, BATBLK.SYS, and MARSFE.SYS.  I'm not the 
greatest with the mathematics and whatnot - better at installing the OSes 
and getting everything wired together. ;)

>    $"/HOM   /$w
> or  505755,,0$w
> (equivalent invocations of the word-search function.  "$" is altmode = escape,
> not dollar)


> 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 

> What do you mean by "I get a BUGCHK whenever I boot  TOPS-10 in KLH10"?  I've
> done that any number of times, and never had a BUGCHK.  What specifically is
> it doing?

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,

> 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)

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

>                                                                Rich
> P. S. OBTW, congratulations!!!


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.)

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

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