Reproducing old machines with newer technology (Re: PDP-12 at the RICM)

Jon Elson elson at
Tue Jul 14 22:18:40 CDT 2015

On 07/14/2015 09:42 PM, ben wrote:
> I guessing ( no schematic handy) that they made the 360 
> register file
> easy to decode and build with latches.
Not just the register file, but the entire machine.  So, all 
the hidden registers in the RTL description,
such as storage address register, storage data register, the 
temp registers that held the data from
a selected local store register, etc. were ALL latches.

By the way, the 360/30 through the 360/50 did not have an 
electronic register file (local store in
IBM terminology).  On the 360/30, they were implemented in a 
separately-addressed extension to
main storage.  On the 360/40 and /50, they were in a small, 
fast core memory unit.  So, on all these machines, the 
register set could only be accessed one location at a time.  
I don't know on the 360/65 whether they had dual ports to 
read the electronic registers two locations at a time, but I 
might guess not.
>> The 11/45 used TTL ICs, so real FFs were available in 
>> that technology,
>> although they may have used latches as well.
> I have seen some 11/?? schematics on bitsavers that the 
> alu uses AOI gates
> and includes a latch term.
yes, the 11/45 was implemented in pretty early TTL, and the 
original 74xx family did have some 6-wide latch devices that 
used less power than the equivalent 6-wide full D FF.


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