The weird stuff I keep finding: 19 bit core memory?

Chris Zach cz at
Tue Oct 20 23:02:31 CDT 2020

Ok, so the MF10 would have been hooked up to a KI10. That makes sense 
then. Still interesting wonder what set of bad decisions led it to my 
box of parts....

Anyone need DZ11's?


On 10/20/2020 11:39 PM, Eric Smith wrote:
> On Tue, Oct 20, 2020 at 8:06 PM Chris Zach via cctalk 
> <cctalk at <mailto:cctalk at>> wrote:
>     The real weird one is a quad board H216. I thought it was a Unibus core
>     memory board,
> Most of the DEC core plane boards were not specific to any particular 
> bus. though there are some exceptions.
>     but it's 8k*19 bits, which means it came from one place:
>     An MA10 memory box. The only one I may have been exposed to was AI (the
>     original KA10).
> I'm pretty sure the H216 was too new to have been used in an MA10 or 
> MB10, but I don't know which core planes or other modules were used. 
> They might have still been using core modules made by external vendors 
> like Ferroxcube.
> The much later MF10 does use the H216, while the MG10 uses the H217 and 
> the MH10 uses the H224.
> The H216 also might have been used in memory systems for a PDP-9 (late 
> in its life) or the PDP-15. The ME15 normally used the H215 18-bit core 
> planes, but I think there was a parity option, which would have used the 
> H216.

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