Commodore D9060
Commodore D9090 Hard Disk Manufactured by Commodore Business Machines [CBM]
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| Manufacturer | Commodore Business Machines, Inc. |
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| Type | Hard disc |
| Release date | 1983 (or earlier) |
| Introductory price | 1995 GBP (1983) 6200 GBP (2017 equivalent) |
| Media | 5¼" Hard disk |
| Storage | 5-7.5 MByte ST-506 MFM |
| Connectivity | IEEE-488 |
| Backward compatibility |
Commodore PET, With special interfacing also VIC-20 and Commodore 64 |
The Commodore D9090 Hard Disk was the only family of hard drives that Commodore made for both the home and business market. The electronics are identical in the D9090 and the D9060 unit; the only difference is the size of the installed hard drive, with a jumper set to distinguish between 4 or 6 disk heads. Originally intended for the metal-cased PET series of computers, they were also usable with the Commodore 64 and later models with an adapter.
Internally the system was made up of four major parts:
Input voltage: 100, 117, 220, 240 V AC
4-pin plug & cable - wiring and voltages follow world standard for large drive power cables, but colours are not standard.
This DOS PCB is made up of several major electronic components:
Disk system buffer = 4 kB (8 × 2114 SRAM chips) Commodore device number selectable between 8 - 11 (on IC 7H : 6532)
Capable of managing 2 x MFM hard drive mechanisms, which is communicated to the user as two combined directories, with one header number = 0 and the other header number = 1 This is unlike other Commodore drives of this era, which required each separate disk directory to be called individually with a command LOAD"0:$",8 and LOAD"1:$",8 for the two drives that reside in device 8. It appears the DOS was never fully completed by Commodore; this is indicated by the way two directories overlap for the one device and the number of blocks free is displayed as if only one hard drive is in use.
The main brain driving this controller is the AMD 'AM2910' (a high-performance 8-bit slice microprogram sequencer) The SASI interface was invented by Shugart that became SEAGATE. SASI eventually became standardized and is known today as SCSI.
Internally the system had a transfer rate of 5.0 Mbit/s from the hard drive to the CBM DOS 3.0 Controller PCB. TANDON was founded in 1975 and became part of Western Digital (WD) in 1988.
Cylinders = 153 (per hard disc) 6 head drive contains 3 x platters, 4 head drive contains 2 platters.
Sectors per Cylinder = 192 (D9090)
Sectors per Cylinder = 128 (D9060)
Sectors per track = 32
Bytes per sector = 256
Access time Track-to-Track, Average: 153 ms, 99 ms
Error Rates: Soft Read: 1×1010 bits Hard Read: 1×1012 bits Seek Errors: 1×106 seeks
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Wikipedia