Front panel switches - what did they do?

Lawrence Wilkinson ljw-cctech at
Wed May 25 12:41:37 CDT 2016

On 25/05/16 01:03, Paul Berger wrote:
> On 2016-05-24 7:44 PM, Chuck Guzis wrote:
>> On 05/24/2016 02:21 PM, Paul Berger wrote:
>>> The CROS cards used in a 360/30 where the same size as an 80 column
>>> card on purpose so you could you a keypunch machine to program the
>>> microcode.
>> But I believe that the CROS cards were mylar, no?
>> --Chuck
> Yes mylar with copper tracks keypunch was used to cut tracks as required.
> Paul
Card (paper) ones did exist! But I suspect they were only for emergency 
FE use.
It may be that the mylar ones were not manual-punch friendly, so you could
make a duplicate to use while you waited for the proper spare to arrive.

There's a photo of a mylar card at

Lawrence Wilkinson                          lawrence at
The IBM 360/30 page         

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