scary warning about bubble memory loop mask, TI 763/765 maint manual

Eric Smith spacewar at
Sun Aug 6 00:56:23 CDT 2017

On Aug 5, 2017 19:42, "Chuck Guzis via cctalk" <cctalk at>

My recollection is that the track data was printed by Intel.  At least
mine came that way.

Both Intel and TI printed the bad loop map/mask on the device label.  Intel
also programmed the map into a special "boot loop" in the device; TI did
not, at least on their 92Kbit devices.

The Intel boot loop was deliberately set up to require a special procedure
to write, so that under normal circumstances it was written once at the
factory, and never had to be written again. However, there was a procedure
to rewrite the boot loop in the field if necessary.

For the TI 763/765 terminal, losing the mask data isn't the problem. The
TEST MASK command lets you type in the mask data if needed.

The problem is that if you type in the mask data wrong on the TI, it can
corrupt the device such that it is NOT FIELD RECOVERABLE. Re-entering the
correct mask and "reformatting" won't fix it.

With Intel devices, there is a special "seed module" and procedure that can
be used to recover bubble devices which have become corrupted. TI just says
that such devices have to be replaced, which is pretty difficult these days.

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