Commodore D9060

Lore & Background

The D9060 was originally designed for the metal-cased PET/CBM series but found its greatest demand among VIC-20, Commodore 64, and Commodore 128 users, who used IEEE-488 interface cartridges such as the Commodore VIC-1112 or third-party interfaces like the Batteries Included Buscard II. Internally, the drive uses a Tandon TM602S or TM603S MFM hard disk mechanism with 4 heads, and the DOS PCB contains two MOS 6502 microprocessors, 8 × 2114 SRAM chips, and three ROMs. A hardware jumper on the DOS PCB selects between 4 or 6 heads, distinguishing the D9060 from the D9090.

The SASI controller, built around an AMD AM2910 sequencer, can manage two MFM hard drive mechanisms, but the DOS was never fully completed; when only one drive is connected, accessing drive unit 1 causes the system to lock up, and the directory display treats two drives as one combined directory. The drive uses the IEEE-488 interface and can be daisy-chained with other devices using different device numbers.

Reader's Guide

The D9060 was highly sought after in the early 1980s by Commodore 64 and 128 users who wanted faster loading and greater storage capacity than the common Commodore 1541 floppy drive. Many bulletin board systems were set up using these hard drives because they could access information quickly and hold far more data than a single-sided floppy disk. By the late 1980s, the Commodore 64 had obsoleted other Commodore 8-bit machines, and older IEEE-488 disk drives and hard drives were acquired by large numbers of C64 owners, putting pressure on the supply of these devices. The D9060 remains wanted by both Commodore 64/128 users and PET family users for whom the drives were originally designed. Its SASI interface, which later evolved into SCSI, and its use of standard MFM drive mechanisms make it a notable early example of a hard drive for home computers.

Did You Know?

• The D9060 and D9090 share identical electronics; only the number of disk heads differs, selected by a jumper.
• The SASI controller can manage two MFM hard drives, but the DOS treats them as one combined directory.
• Any 4- or 6-head MFM drive mechanism can be used as a replacement.
• The drive uses two MOS 6502 microprocessors running at 1 MHz.