Omnibus core memory compatibility?

Pete Turnbull pete at dunnington.plus.com
Sat Dec 6 11:11:18 CST 2008


On 06/12/2008 16:23, Philipp Hachtmann wrote:
> G104 X/Y drivers
> G227 Sense/Inhibit
> G619A 4K core stack
> 
> The 4K stack is broken and lost forever.
> 
> But I have a spare G646C "4K or 8" Stack sitting around.
> I *think* it has 8K.

There should be a sticker, usually a white paper DEC sticker but 
sometimes a silvery sticker, on the back, with a DEC part number.  8Kx12 
stacks say H212 or H212A.

> Does anyone know if I could use that stack with the rest of the package, 
> using only 4K of the memory?
> 
> Does anyone have schematics for the 8K core system? In my documentation 
> I have only information about the 4K system.

I don't know if you can use that stack with the 4K drivers and 
sense/inhibit card, but the print set with schematics for the 8K system 
(MM8-EJ) is on David Gesswein's site and mirrored at Highgate.  So is 
the one for the 4K (MM8-E), which seems to include MM8-EJ diagrams.

http://www.pdp8online.com/pdp8cgi/query_docs/view.pl?id=243

You could compare the top connections to the 4K schematics.  I'd be 
interested to know myself.  The notes on the 8K schematic list 
compatibilities that don't include the 4K drivers etc, but that may only 
be because you wouldn't get the full 8K with 4K drivers or sense/inhibit 
controllers.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York



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