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

14 Aug 2006

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Subject: Re: PDP-8 /e/f/m memory
   From: "Ethan Dicks" <ethan.dicks at gmail.com>
   Date: Tue, 15 Aug 2006 12:54:00 +1200
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On 8/15/06, Patrick Finnegan <pat at computer-refuge.org> wrote:
  On Monday 14 August 2006 19:43, 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.   
I have a bag of them I salvaged from old 386 and 486s and most are 
either low power or CMOS.  I've bumped into a few of the older NMOS
parts that are not low power but they do gow down in power when 
deselected.  Nothing like the old 2114 or 2147 or 2167.

However power it not a prime consideration as the lamps on the FP
are a big load compared to most everthing else.

For me it's board space, heat and a one card solution.

Allison

...
 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.

-ethan 