Strange peripherals… Commodore hard drives

When we consider hard disks for the Commodore C64/C128, one name always pops up: the HD20 from CMD (Creative Micro Designs).

This drive had an internal 6502A CPU, 64 KB of RAM and an EPROM containing the boot system for the drive and it sported a whopping 20 MB, which could be extended up to 4 GB.
You could play around with this drive in 4 different modes, such as a classic 1541, 1571 and 1581 mode, for which you could split up the 20 MB in 255 partitions, with each then having a “disk image”. (see the article “Strange peripherals… the HD20 hard disk“)

All this happened in the early 90s and the drive is widely considered to be THE drive for the breadbox. With all this firepower, one would almost forget that Commodore themselves made hard drives too, albeit for their PET-range of computers: the CBM 9060 and the CBM 9090 drives.
Both drives however did not perform superbly (some would outright fail after a period of continuous use) and it would come as no surprise then that Commodore discontinued the production of these drives for their PET-line.

Interest for these drives rekindled in the late 80s though, as professional users of the C64 were looking at mass storage capabilities (i.e. databases) for their breadboxes.
So a couple of firms saw the potential of these drives for the up-market segment and set out to refurbish them, resulting in higher capacity and faster drives.

Using a 9060/9090 hard drive provided you with two new logical drives (0 and 1) each with 38884 blocks available, resulting in roughly 20 MB of space.
Speed wise, it was not faster than the regular 1541 and unlike the HD20, you could not upgrade it with JiffDOS. Nonetheless, the main use and target audience for this drive was the professional user, who needed huge amounts of trustworthy storage space (and could afford the 500 Euro price tag). As most of us have experienced, the good old 5.25” disk surely was not the prime medium for that purpose, so these drives nicely bridged that gap… at least until the HD20 came along.

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4 Responses to Strange peripherals… Commodore hard drives

  1. Not related to this post but I found this in the trash a while ago, put a battery in it, worked like a charm.
    It’s a Commodore SR4120D and it has the serial no. 144764 printed underneath.
    Do you know anything more about it?

  2. Robby "The C= guy"

    That’s a nice scientific calculator you have there!
    Some more info on the calculator itself right here:
    As you probably know, Commodore was into calculators before moving into computers. In the early 70s they got their chips from Texas Instruments, but when TI decided to start selling their own calculators, which were cheaper than Commodore’s it initiated the “Calculator Wars”.

  3. There is a knowledge base article on the HD20 here :

    Great article, Thank You!

  4. Pingback: Strange peripherals… the Lt. Kernal hard drive | MOS 6502

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