Core memory emulator using non volatile ram.

allison allisonportable at
Sun Dec 16 22:04:32 CST 2018

On 12/16/2018 10:07 PM, ben via cctech wrote:
> On 12/16/2018 8:00 PM, allison via cctech wrote:
>> In the end, current generation CMOS ram is the easy out, battery is
>> small, cost is small,  and
>> produces much less of the heat that is killer to systems.   The only
>> reason to do that is core
>> cost big if you can find it for your machine.  I can cost more if you
>> want to run an OS that
>> needs a fair amount of it.  AC as well as it can help heat the room and
>> also power as in
>> makes the meter spin.
>> So much lathering and speculation about what and how.  When the point is
>> totally missed.
>> Allison
> What programs or operating sytems require non volatile core?
> Did DEC have any BOOTSTRAP programs in prom for the 8?
> A small prom and regular slow mos memory may be the solution.
> Ben.

Non volitility was handy if you wanted to power down go home and restart
where you were
the next day but at the OS level that was never a consideration.

CMOS is MOS!  Current generation parts are cheap and easy to use.  Its
not a speed issue as
core was so slow, PDP-8 the fastest core was 1.5uS and even current cmos
(5101) was under 1uS.
No advanatage for slow memory as everything from 1978 on was likely much
faster than an 8e
needed anyway. 

The easy way if obvious use cmos as its cheap and common as house
flies.  Leave out the
small lithium cell. 

The problem is PROM cards for PDP-8 omnibus was not common at at then
then time cheap
and used parts likely to be unobtainium now.  The machines that had it
used an abbreviated
front panel  maybe 12 sense switches for the OSR instruction and a
boot/start switch.  Not many
made and FS contract required the full panel to do checkout and fix.  So
cost wise the boot card
was not common.  Call it an artifact of systems then.

The loader for most stuff was small anyway, toggle it in, usually rim or
bin loaders.  Run the reader
and that loaded whatever.

Typical small non disk systems were CPU, TTY and maybe a high speed
reader.  Next level added TU56
or maybe RX01 floppy, from there a DF32 disk and maybe a RK05 or two. 

The user interacted with them the box ala the CPU was a small part of
that interaction/experience.


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