DEC MM15 core mem found

Rich Alderson RichA at
Wed Dec 9 14:32:15 CST 2015

From: Pontus Pihlgren
Sent: Tuesday, December 08, 2015 11:52 PM

> On Tue, Dec 08, 2015 at 09:42:27PM +0000, Rich Alderson wrote:

>> Flip Chip technology was invented for the PDP-7, after the failure of
>> the large System Modules used in the PDP-6.

> What where the failure(s) with System Modules in the PDP-6? cost? 
> reliabilty?

Soldered edge connectors on 2 sides of the board.  In order to remove or
repair a board in the middle of a module (say, a bit in an accumulator),
you had to carefully unsolder all the connections to boards next to it and
move the wiring out of the way.

Seriously fragile.

>> If you'd like to visit the museum, I'll happily show you the internals of
>> a running PDP-7. :-)

> Oh yes! If/when I cross the atlantic you will have to show me internals 
> of _everything_. Can you buy a five-day pass? :-)

Annual memberships are available.  I'll send you costs of 1 day vs.
membership privately, or you can look them up on our site under the
"Visit Us" and "Get Involved" tabs on the home page.


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

mailto:RichA at

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