GA21-9182 (8”) floppies¶
IBM invented the floppy disk and used it for microcode, until commercial pressure from Mohawk Data Systems made them also use it for key-punch data exchange (Model 3741 etc.)
GA21-9182, which underwent a handful of revisions as the floppy disk expended with double density and double sides, lays down both the physical format and a logical format for data exchange, clearly inspired by tape-labels, but with random access and bad sector handling.
Cylinder zero is called “The Index Cylinder” and head zero is always formatted in single density with 26 sectors of 128 bytes.
IBM seems to have used the GA21-9182 format slavishly, but in some cases, like the DisplayWriter (Model 6580 etc.) somewhat performatively.
Other vendors seem to have used it only to the extent they needed to for data exchange with IBM systems.
Usage¶
from autoarchaeologist.vendor.ibm import ga21_9182
…
self.add_examiner(*ga21_9182.ALL)
Notes¶
Bad sector handling is not implemented.
Test input¶
COMPANY/IBM/SYSTEM3
