PDP-8 /e/f/m memory

Allison ajp166 at bellatlantic.net
Tue Aug 15 07:33:37 CDT 2006


>
>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



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