Posted By
JamesC
on 2003-09-08
|  Re: Strange 1551
Regarding the second auction you posted, I presume that the seller has simply mismatched the disk drive with the computer, not knowing that they are not compatiable.
Commodore dropped the TCBM standard (and hence development for the parallel disk drive for the C64) when the 264 series was dropped. The only reason 1551s were sold in any quantity in Europe is because of all the 264's being dumped there. The 1551 was never released here because the computers were quietly pulled from dealer shelves in March of 1985, after only 6 months on the market. With the 128 soon to appear on the horizon, Commodore didn't want upset dealers refusing to carry yet ANOTHER orphan machine.
And THAT'S why the 1542, or a TCBM drive for the 64, never appeared. When the Tramiels left, the computers were shoved out the door only to recover development costs and fulfil minimum sales commitments from the software suppliers (Tri-Micro, Scott Adams, Island Graphic, etc).
Itonically enough the idea was persued here in the States by an independent company. If you can find a Lt. Kernal hard drive, it uses the C64's parallel port directly, instead of the serial port or an IEEE adapter. With a 10 meg hard drive, it sold for US$1000.
Another thought as to why the TCBM standard wasn't persued by Commodore -- there were several companies that sold cardridge port expansions here.... add two, three, or 4 cartridge slots to the C64, add in am operating system that doesn't directly support the parallel disk drive to start with, and system stability becomes eerily Windows-like in its' kludges, core code upgrades, and work-arounds.
As I've mentioned before, Commodore US released all Plus/4 disk software with copy protection code dependant on the 1541's ROM. Evidently Commodore software development knew something that Commodore marketing did not. 
Regarding the 1551's ROM, all the ROM code does is read info from the disk and put it in a buffer, and pull information from a buffer and write it to the disk. It's the other chips and wiring in the system that makes the drive serial or parallel. If the same code is run on a 6502 as opposed to a 6510, the code itself doesn't know that it's running slower. Evidence: 1551s run in the US without any 50/60Hz adjustments (well two of the three known 1551s, mine is still acting very strangely). As long as the proper voltage is coming out of the transformer, the disk drive merrily lights up and turns the disk, reads or writes just as a 1541 is expected to. Bo Zimmerman and Jim Hehl made no internal mods to their 1551s to make them work here.
Even if it doesn't work, it would make a nice experiment. 1541s are cheap enough here to try it; I have 2 plus 2 1541-IIs to experiment with.
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