The Commodore D9060/D9090 Hard Disks were the only family of hard drives that Commodore made for both the home and business market. The electronics are identical in the D9060 and the larger D9090 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/CBM series of computers, they are compatible with the VIC-20, Commodore 64 and later models with an adapter.
Technical data
on the D9060; 153 Cylinders × 4 Heads × 32 Sectors × 256 Bytes/sector equals 7.52 MB.
on the D9090; 153 Cylinders × 6 Heads × 32 Sectors × 256 Bytes/sector equals 5.01 MB.
on the D9060; about 20% of the hard disk is never used, on the D9090 it is about 25%.
Internally the system was made up of four major parts:
8 × 2114 SRAM chips 4 kB DOS use, system disk buffers
Commodore device number selectable between 8 - 11
SASI controller
The main brain driving this controller is the AMD 'AM2910' The SASI interface was invented by Shugart which would later become Seagate. SASI eventually became standardized and is known today as SCSI.
Connecting two hard drives to one SASI controller
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 DOS will also "lock up" if an attempt is made to access drive unit 1 when there is just the one hard drive unit connected as drive unit 0.
Hard drive
The unit uses Tandon TM602S/TM603S hard disk drive units. Tandon was founded in 1975 and became part of Western Digital in 1988. Data is encoded to the disk platters using the MFM disk format. Internally the system had a transfer rate of 5.0 Mbit/s from the hard disk drive to the CBM DOS 3.0 Controller PCB. Any 4 or 6 head MFM drive mechanism can be used as a replacement mechanism. Cylinders = 153 6 head drive contains 3 platters, 4 head drive contains 2 platters. Sectors per cylinder = 192 Sectors per cylinder = 128 Sectors per track = 32 Bytes per sector = 256 Access time Track-to-Track, Average: 153 ms, 99 ms Error Rates: Soft Read: Hard Read: Seek Errors: Recording density: 7690 BPI Transfer speed: 5 Mbit/s +12V D. C. +/- 10% 1.5 amps tyical, 5 amps maximum for 10 seconds with no more than 5 millivolts PARD* +5V D. C. +/- 5%.. 8 amps typical with no more than 50 millivolts PARD*
Periodic and Random Deviation.
Environmental: Ambient Temperature: Operating: 16 °C to 46 °C Nonoperating: -35.4⁰C to 60 °C Relative Humidity: 8% to 80% Maximum Wet Bulb Temperature: 26 ⁰C without condensation True: 0.0 - 0.4 V Imax=40mA maximum False: 2.5-5.25 V Imax=0mA open Control signal electrical for single ended signals: 7438 driver into a maximum of cable into a +5V..220 ohm..Signal..330 ohm terminator..GND into a 74LS14 load.
Formatting
Despite the small storage space of these legacy hard drives, formatting either can require a fair amount of patience from the user:
D9060 Formatting takes approximately 1 hour.
D9090 Formatting takes approximately 1 hour and 20 minutes.
Partitions and subdirectories
Due to the structure of the onboard DOS 3.0, there is only one main partition which contains the directory and all the saved files. There are no subdirectories so eventually you run into trouble when you type LOAD"$",8 and LIST, the directory list fills the screen and then scrolls away. You can pause the directory listing as with any Commodore computer. But if you have scores or hundreds of files saved, then the user must wait some time until the entire directory listing has finished scrolling.
Using larger disk mechanisms
With minor changes to the CBM DOS ROM code, larger capacity hard disk drives could be swapped into the D9060/D9090 unit. This was done by finding drives with 8 heads and 256 cylinders. The CBM DOS would support these numbers if "hard coded" into the ROM. Nothing larger could be accommodated without major changes to the drive code. In the 1980s, an Arizona company named Copperstate Cash Register was selling upgraded units to the business and BBS operator community.
The drive used and IEEE–488 interface to communicate with computers and the Hewlett-Packard Interface Bus ). The transfer rate was 1.2 kB per second from the D9060/D9090. These hard drives can be daisy chained on the interface with each device using a different device number. The D9060/D9090 were designed for use on the Commodore CBM/PET family of computers, but because these metal-cased family of computers were obsoleted by the VIC-20 and the Commodore 64, the greatest demand for these drives came from the biggest home computer user market in the world at the time, the VIC-20, C64 and C128 users. As a result, Several companies built interfaces that effectively give a VIC-20 and Commodore 64/128 an IEEE-488 port. The first produced was the VIC-20 IEEE 488 cartridge, model number "VIC-1112", produced by Commodore. Commodore 64 IEEE-488 interface cartridges were made by various companies. The original Commodore 64/128 IEEE Cartridge was produced later and were packaged with SFD-1001disk drives in Europe only, that would explain why this unit was unknown in the U.S.
Batteries Included - Buscard II Interface. and and a
Some other interfaces without pictures available:
E-LINK Serial to IEEE Interface.
INTERPOD - A standalone interface box, that connects the CBM serial to parallel IEEE-488 and serial RS-232. It uses the 6502 CPU, 6532 RIOT, 6522 VIA, 6850 ACIA and chips.
Richvale Telecommunications - C64-LINK II - 6821 PIA, EPROM
Commodore 64/128 usage
The D9060 & D9090 Hard Drives were highly sought after in the early 1980s by people using the Commodore 64 and Commodore 128 who wanted to taste the luxury of having all their utilities and games in one place, and being able to load these files and games at high speed, with an overall loading speed faster than the standard drive that most people were using Commodore 1541 with "664 BLOCKS FREE" Where as a D9090 hard Drive has 29,162 BLOCKS FREE Which is why many bulletin board systems were set up using these hard drives as they could access information quickly and could hold massively more information compared to the 1541 disk drive which could only access on one side of a floppy disk at one time. By the late 1980s, the Commodore 64 had obsoleted all other Commodore 8-bit machines mainly because of the sheer number of users worldwide and also the market support from so many 3rd party software & hardware companies. As a result, the older IEEE-488 disk drives and hard drives were being acquired by large numbers of C64 owners to connect to their computer using an IEEE-488 Interface. This has put pressure on the supply of these devices as nowadays they are wanted by both Commodore 64/128 users and also needed by people using the PET family of machines, that these drives were specifically designed for.
Price when new
The oldest pricing reference found for this article was titled "Commodore Price List 1-september 1983"
D9090 Hard Disk Drive 7.5 Megabytes = $5813, £2495
Software, drivers & technical support
Commodore 64 based software for drive management, file transfers & repair diagnosis is available from the . A software & cable combination exists which allows using a common x86 compatible PC as a Virtual IEEE-488 hard drive. See here:
