Front panel switches - what did they do?

Chuck Guzis cclist at
Tue May 24 14:13:29 CDT 2016

On 05/24/2016 11:39 AM, Eric Smith wrote:
> On Tue, May 24, 2016 at 12:25 PM, Paul Koning
> <paulkoning at> wrote:
>>> On May 24, 2016, at 2:07 PM, Chuck Guzis <cclist at>
>>> wrote: ...and the "transformer" ROS used on the 360/40 (and
>>> others).
>> You mean "Core rope memory"?
> IBM's TROS and Core Rope Memory use the same principle, but the 
> physical construction is significantly different. Core rope memory
> was very labor-intensive to manufacture, while TROS was not.

There's a photo here;

I seem to recall that reworking the 360/30 microprogramming was
preferred by tinkerers over the 360/40 was primarily that CROS was
easier to work with than TROS.

I don't recall what the RCA Spectrolas used.


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