SD Card disk drive for C-64?

Jim Brain brain at
Sat Jan 23 21:28:08 CST 2016

On 1/23/2016 8:58 PM, Eric Christopherson wrote:
> On Sat, Jan 23, 2016, Jim Brain wrote:
>> On 1/23/2016 7:15 PM, drlegendre . wrote:
>>> " I am saying don't make a permanent hardware change to a 1541 that
>>> does not have the switches unless you really want it to be permanent
>>> because there is a software method of assigning drives that is good enough
>>> most of the time.  BUT if you must make it permanent and you don't have the
>>> external switches, consider adding some form of external switch so you
>>> don't ever have to open the case again to put it back to the default."
>>> Well then, we're having a major agreement. ;-)
>>> The device ID switch is the ultimate fix for Commodore drives, and I'm
>>> really not sure why CBM didn't incorporate one into the design - at least
>> >from the 1540 on upwards. Can't have cost much to add a discretely located
>>> access hole (or a knock-out) in the case, along with a 2-place DIP switch
>>> for controlling device ID.
>> But, they did.  The 1541-II, 71, and the 81 have switches.
>> I would disagree on your point that Commodore should have made it part of
>> the design...
>> Let's travel back in time.
>> After the PET intro, Peddle designs a drive, a beast of a device, with 2
>> CPUs and it costs a fortune.  Peddle is convinced a smart drive is best, and
>> the delay allows other manufactures to create "dumb" drive options (saw one
>> at World of Commodore, forgot the name).
> How did these dumb drives interface with the computer at a software
> level? I'd think a DOS would need to be loaded somehow.
The one I saw at the WoC was a 8" drive connected to a PSU and the cable 
attached to a small PCB that replaced the editor ROM in the PET.  THe 
PCB mapped a controller into the address space and the editor ROM was 
patched to support a DOS.

It was an interesting setup.  Mike N (of had the unit. Steve 
Gray on here was there too and could provide more details.


Jim Brain
brain at

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