Commodore 4040 Disk Subsystem The CBM 4040 was a dual-drive full-height 5-1/4" disk subsystem intended for use with the PET-range of computers. It incorporated an IEEE-488 interface and each disk could hold 170k. Commodore at one point was developing a half-height version of the 4040, labled the CBM 4040LP, but the drive never went into production.

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