SD Card disk drive for C-64?

drlegendre . drlegendre at
Sat Jan 23 20:20:27 CST 2016


That's an interesting and colorful narrative, and much of it makes good
sense - in the giddy days of the 1980s home computer market, and for CBM in
particular. But speaking as one who was fairly hot & heavy into the VIC-20
(and then almost immediately the C-64), this 'drive ID' issue has
more-or-less dogged us since day one.

While it's true that +most+ end-users couldn't or didn't buy a second 1541,
it was very common to connect two or more drives to a single machine for
demonstrations, software shows, user group meetings or what might have been
the 1980's equivalent of the LAN party.. where we shared & swapped
software. And on top of that, as time wore on, there were a number of
programs that supported multiple drives.

So we can agree that Jack, being Jack, had his reasons. But ultimately, I
still see this decision as short-sighted. There's a reason that the circuit
board jumper pads were well-publicized, as were the many text files on
adding device ID switches to the 1541.

On Sat, Jan 23, 2016 at 7:33 PM, Jim Brain <brain at> 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).
> Tramiel is mad, and the drive doesn;t sell terribly well at first.
> When the VIC-20 comes out, the drive is just marketing materials. Why
> would someone want a business storage system for a home computer basically
> built because Jack needs to unload a bunch of VIC-I ICs that he can't sell
> to video game firms?
> But, people asked for it, and CBM delivered, taking Peddles IEEE design,
> ditching the IEEE cabling (Jack: "Get OFF that bus", as the cables from
> Belden/Beldin(sp?) cost a mint and supplies had been spotty at times).  The
> unit is retooled to use 1 drive, 1 CPU (and in the process the changes
> introduce the fabled "save with replace" bug.  Enter the 1540
> But, the designers put little jumper pads on the drive to set dev number,
> as they were very sure most people would never buy two of them.
> Then the 64.  Paddle's ColorPET design loses out to a hacked VIC-20, which
> became the 64
> Now the drive seems more useful, and can be made more cheaply.  As well,
> other units in the marketplace have drives, so it is a competitive need.
> All is well, though, as the 1540 is already in production. Dump some gray
> tan/gray colorant in the injection mold machines, and you're done.  That's
> classic Jack.
> The 1540 has a problem though.  The bit banging protocol (introduced late
> in the 1540 design cycle after it was determined that the VIC shift
> register has issues) fails on the 64.  high/low times are 20uS/20uS, and
> sometimes the CPU is stopped for 50uS on the 64. Enter the 1541.  No
> changes except the ROM, which slows down sends from the drive to the 64 to
> 60/60uS clock.  Jack is done.  He doesn't care if people buy them per se,
> just that the drive is there so he can tout it being there as he competes
> with the Apples and Ataris.
> So, at the time, with the drive being as much as the computer, no one
> thought people would buy more than 1, and thus no need to pay for extra
> parts (switches) and changing the molds.
> With the C128 and the case redesigns, people were buying multiple drives,
> and it was a selling point, so the switches made their appearance.
> Jim

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