PDP-8 /e/f/m memory - test-drb@ccmp.vtda.org

15 Aug 2006

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Subject: Re: PDP-8 /e/f/m memory
   From: Dave McGuire <mcguire at neurotica.com>
   Date: Mon, 14 Aug 2006 20:59:31 -0400
     To: "General Discussion: On-Topic Posts Only" <cctech at
classiccmp.org>

On Aug 14, 2006, at 8:54 PM, Ethan Dicks wrote:
    Why not use a pair of 62256s?  32Kx16 and ignore 4
bits.  It'd even   be
  easy to use a Dallas DS1210 or something like it
to provide battery
 backup. 
 I'd probably do something like what the SBC-6120 does... use some 
 typical 486
 motherboard cache SRAM.   Cheap, and relatively easy to find. :)

 You'd end up with one or two chips to do 32k x 12. 
 32Kx8 are easy to find as old cache RAM.  They are not, however, low
 power, and would not be the best solution if you wanted to hang a
 battery off of them.  OTOH, unless you are using paper tape software
 only, chances are you have a mass storage device and are booting into
 OS/8 and don't really need battery backup. 
   True, but I think the idea there was to duplicate the functionality 
of core, i.e. the nonvolatility in this case. 
Presumed only.  Though with the parts I ahve it would be easy it was not
a significant consideration.

...
    That said, though, I've not found 486
motherboard cache memory to be 
particularly easy to find.  I did, however, buy a box of about 80 6264 
chips on eBay a few months ago for fifteen bucks.  And 62256s are still 
manufactured, as far as I'm aware. 
Both are easy to find.  My supply of RAM came off some really nice but
excess 486 boards must from the 1995-1998 timeframe.

Allison