Re: IBM 1620; was: Early Programming Books

[Paul Koning via cctalk]

> On Jun 21, 2021, at 2:43 PM, Chuck Guzis via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> On 6/21/21 10:55 AM, Paul Koning via cctalk wrote:
>> 
> memory. Nobody explained why that was a real problem.
>> 
>> Core memory is fairly sensitive to temperature.  In the case of the 1620, 
>> there is a heating system that brings the core memory box up to its 
>> operating temperature, which is why it takes several minutes after you turn 
>> on power before the machine will run.
>> 
>> Possibly the fan problem meant the temperature control system was no longer 
>> adequate.
> 
> For some (jprobably hallucinatory) reason, I thought there was a project
> at CHM to replace the 1620 core stack with semiconductor memory.   Guess
> that never happened.
> 
> --Chuck

Perhaps you were thinking about the CDC 6500 at the late lamented LCM?  That 
got some replacement stacks, which was an interesting puzzle because the read 
data connection out of the memory modules is a differential analog signal 
carrying the sense wire data, so the replacement module had to produce signals 
of that form.

        paul