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Enhancer 2000 with 1541-II ROM

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While reading around about the Enhancer 2000 disk drive, I found a few posts which reference some controversy over its initial release. Supposedly, the original drives had an exact copy of the 1541-II ROM which elicited a legal response from Commodore.


In another thread I made mention of problems using the Enhancer 2000 with the XU1541 via the OpenCBM USB library. My initial experience with its compatibility problem was back in 1987 trying to load GEOS. I really have no idea why I keep the damned thing, there is just some weird appeal to it.


Anyway, I decided tonight that while I had things disheveled around the bench I would go ahead and swap in a 1541-II ROM, 251968-03, reported to be "16K ROM DOS 2.6 rev. 4, $C000-$FFFF".


The drive starts up with the exception of the LED indicators: only the error and power LEDs illuminate, then the error LED goes out. I expected that since the 1541-II does not have two activity LEDs. It responds to the serial bus reporting the proper 1541-II DOS status string. It responds to most commands just fine, until disk access is required.


The drive motor spins up but the head will not step. As an aside, I suspect the red drive LED is tied somehow to the stepper drive circuits, which means DOS is ignorant of its existence. Again, makes sense give the 1541-II's LEDs. I have not done any more investigation, I just put the Enhancer DOS ROM back in place.


So, if the assertions are true, then I would have one of the later models of the Enhancer 2000. The chips soldered on the board are all dated 1984 (4584 on the 6522s,) but that does not give real indication of the date of manufacture of the drive, itself.


The main board has the strings "708V" and "073FIJC EP01" screened on, and a stamp "A0945". The drive is a Chinon F-051A II.


Thinking about the possibility of two ROMs, one an exact copy of the 1541-II ROM and one a re-worked and mostly-compatible version. I can see that. But what I cannot see is a re-worked second release with electronically incompatible head movement -- even if just inverted -- as that would require two releases of the re-worked Enhancer DOS, and, while not impossible, I cannot imagine Comtel Group would want that hassle.


I may play again, later. It could be something about the drive mechanism and that ROM: perhaps an earlier version of the 1541-II ROM would work properly, or maybe there is something screwy about the track zero sensor. I dunno, but I may be spending too much time on the matter when I could just turn up a real 1541-II and call it a day. But, why? Because it's there.


EDIT: Just read here, apparently the -03 ROM cannot have the track zero sensor active. Now my curiosity is piqued, again, but I do not have an earlier version of the 1541-II ROM.

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