Commodore D9090 & D9060 Hard Drive

Last Updated:1-10-18

D9090 Hard Drive - 7.5 MB

D9060 Hard Drive - 5.0 MB

CPU: 2x 6502 @ 1MHz
ROM: 16 kB
RAM: 4 kB

Data Transfer rate

Internal: 5MB /sec
External : 1.2k /sec

External : 5k /sec (with CMD SUperCPU)

Data Bus: IEEE-488

Spin Speed: 3,600 RPM

Computer Compatability: PET, 4000 & 8000 Family, B128.

C64 & C128 with IEEE Cartridge or Serial to IEEE Interface

D9060 Heads: 4

D9060 Storage: 19,442 Blocks free

D9090 Heads: 6

D9090 Storage: 29,162 Blocks free


DEVICE 8 , 9, 10, 11    Click here to learn how to change the device number of the D9060/D9090


4 or 6 HEADS    Click here to learn how to replace the actual HARD DRIVE mechanism with many other Types & Sizes of MFM Hard Drives commonly found.


Other device Jumpers on the SASI board of the D9060/D9090


Another big advantage of using these IEEE-488 Disk Drivers on a Commodore 64 is the improved Loading speed, because the IEEE-488 is a Parallel loading cable. Loading Speed can be 5-10 times faster than a 1541, depending on the Drive type you are loading from, ie- Floppy Drive or Hard Drive.

C64 BASED - D9060 & D9090 TOOLS

D9090 TOOLS V2.1 This file is a good All-round utility, excellent for formatting the HD.

D9090  UNI-COPY This will copy from IEEE devies to Serial devices.

D9090 DIAGNOSTIC A utility to help repair a D9090 or D9060 hard drive


D9060 & D9090 - Firmware

D9090 ROMS This file contains the 3 D9090/D9060 ROM's from the DOS PCB.

D9090 BPROMS This file contains the 5 D9090/D9060 BPROM's from the SASI PCB.

D9090 PARTS LIST & COMPONENT OVERLAY This file conrtains very clear overlay diagrams for DOS & SASI PCB's,  that I Just recently created my self & a Parts list also.

D9090 Technical manual


D9060 & D9090 - Data Transfer Cable

The D9060 & D9090 will connect Directly to the original Families of Commodore Computers, like the: PET,700, 4000 & 8000 Family, but when connecting it to a C64 or C128, you need to use an IEEE-488 Cartridge or Interface of some sort. Which uses an IEEE-488 Parallel cable. For more information on IEEE-488 Interfaces for the C64, Click here.

<- This is what an IEEE-488 Parallel Port looks like.

D9060 & D9090 - LINKS



Commodore D9090 Hard Disk Drive & D9060 Hard Disk Drive (Manufactured by COMMODORE BUSINESS MACHINES [CBM] )

This was the first and last family of Hard Drive that Commodore made for both the Home & Business market. The Electronics are identical in a D9090 and D9060 unit, the only difference is the size of Hard Drive mechanism installed, and a jumper set on the DOS board to distinguish between 4 or 6 heads.


D9090 - TANDON TM603S -- 3,600 ----- 6 --------- 9.6MB ---_____________ 7.52MB____________ = 29,162 BLOCKS Free
D9060 - TANDON TM602S -- 3,600 ----- 4 --------- 6.4MB ---_____________ 5.01MB____________ = 19,442 BLOCKS Free

(on the D9090 25% of the Hard Disc is never used).


In both the D9090 & D9060, MFM Hard Drives are used which are identical to the type used on IBM PC's & Compatibles of the 286 and 386 Family. These utilize a system of two cables that connect the Drives to the controller. One Cable is for Data, the other is for Motor control.

Internally the system was made up of Four major parts:- (1) CBM DOS 3.0 PCB, (2) SASI CONTROLLER, (3) HARD DRIVE, (4) POWER SUPPLY
Input Voltages

100 Volts AC
117 Volts AC
220 Volts AC
240 Volts AC



4 Pin molex plug & cable - wiring and voltages follow world standard for large drive power cables, but colours not standard.

1 - 5 Volts

2 - Ground (black)

3 - Ground (black)

4 - 12 volts


CBM-DOS 113x85.JPG

Ths DOS PCB was made up of several major electronic components: 3 x ROM's (Two for CBM DOS communication with host computer, One for SASI communications for Hard Drive formatting- Track & Sector layout, 4 or 6 heads.) 4 or 6 heads is selectable only by a hardware jumper located on the front of the DOS PCB. 2 x MOS 6502 Microprocessors 2 x 6532 RIOT I/O Chip 1 x 6522 I/O chip Disk system buffer = 4k ( 8 x 2114 RAM chips) Commodore Device number selectable from 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 Which is strange because most Commodore drives of this era required each seperate disk Directory to be called individually by a command LOAD"$0",8 and LOAD"$1",8 for the two drives that reside in Device 8. As a result it looks like the DOS was never fully completed by Commodore, which is evident when you save to the hard drive only to find that the two directories overlap for the one device and the number of blocks free is only 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 Technology was invented by SHUGART who became SEAGATE (SASI, which eventually became standardized and known today as SCSI ) They also went on to create the company ADAPTEC.


Internally the system had a transfer rate of 5.0 MB per second, from Hard Drive to CBM DOS 3.0 Controller PCB. (TANDON became WESTERN DIGITAL.)

HARD DISC (Inside the hard drive)

Cylinders = 153 (per hard disc) 6 head drive contains 3 x hard discs, 4 head drive contains 2 hard discs.

Sectors per Cylinder = 192 (D9090)

Sectors per Cylinder = 128 (D9060)

Sectors per track = 32

Bytes per sector = 256


IEEE 488

IEEE 488 bus [24 wire cable] - (Transfer rate 1.2 K per second from D9090/D9060 to Computer - 8 Data lines

D9090/D9060 Hard Drives can be daisy chained, the same as the Commodore Serial bus used on the 1541, 1571, 1581 Family of floppy drives.

PET The D9090 & D9060 were designed for usage primarily on the Commodore PET Family of computers, but because these Metal cased family of machines were obsoleted by the VIC20 & COMMODORE 64, the greatest demand for these drives came from the biggest home computer user market in the world at the time, ie - The Commodore 64 User. As a result, Several companies built interfaces that effectively give a VIC-20 & Commodore 64/128 an IEEE-488 Port. Commodore created a VIC20 IEEE 488 cartridge : Model number : VIC1112
IEEE-488 (VIC-20)
VIC1112 cartridge
IEEE-488 (COMMODORE 64/128)

The Commodore 64 IEEE-488 Cartridges were made by various companies, but Commodore themselves never made one for the Commodore 64/128 family. Here are a list of a few:








Some other Interfaces, no Pictures available:-

E-LINK Serial to IEEE Interface. (Contains 65C02, 6522 and 4K ROM)

Buscard II Interface. (Contains 6532, 6821 and 8K ROM, & 256 byte PROM)


INTERPOD - An Interface box, that converts IEEE-488 to CBM (IEC) Serial & RS-232 Serial.



The D9090 & D9060 Hard Drive was highly sought after in the early 1980's by the huge number of people using the Commodore 64 & Commodore 128 who wanted to taste the luxury of having all their Utilities & Games in one place, and being able to load these files/Games at high speed, with an overall loading speed 5 times faster than the standard drive that most people were using, Model : 1541 ( 664 BLOCKS FREE ) Where as a D9090 hard Drive has 29,162 BLOCKS FREE !!! Which is why many BBS's (Bulletin Board Systems) were set up on these hard drives because they could access information so fast and could hold so much information compared to the 1541 disk drive which could only access 170k on one side of one disk at one time. By the Late 1980's, the Commodore 64 had obsoleted all other Commodore 8-Bit machines mainly because of the sheer number of users world wide and also the market support from so many 3rd party software & hardware companies. As a result, the older IEEE-488 Disk Drives & 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 now a days 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.



Due to the structure of the on-board DOS 3.0, there is only one main Partition which contins the Directory and all files saved. There are no Sub Directories so eventually you run in to 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 100 Files saved, then you have to wait some time until the Directory Listing reaches the bottom.

PRICE WHEN NEW The oldest Price list I found was titled "COMMODORE PRICE LIST 1-SEPTEMBER 1983"

D9060 Hard Disk Drive 5 Megabytes = $4648 (Australia), £1995 (UK)

D9090 Hard Disk Drive 7.5 Megabytes = $5813 (Australia), £2495 (UK)


Any 4 or 6 head MFM drive mechanism can be used as a replacement mechanism.


D9090 (6 heads) Formatting takes 1 hour and 20 minutes !!! so be very very very very patient...

D9060 (4 heads) Formatting takes about 1 hour !!! so again you need to be very patient...

I would highly recommend Removing the Hard Drive Mechanism and first Formatting it on a PC, which will do it much faster than you can using the D9090 on a PET or C64 computer. This will let you find any READ/WRITE errors and the drive will then be more reliable when re-inserted into the D9090 unit. This will also prevent FORMAT FAILURE when the unit is being Formatted on a Commodore Computer system.


C64 based Software for Drive management, File transfers & Repair diagnosis is available here at the SPACE_TAXI website.

A program & cable exists which lets you use a common IBM compatible PC as a Virtual IEEE-488 Hard Drive, from here :


This Page last updated : 29-11-2011