Hello Jim, > Many clone drives used a direct copy, an obfuscated copy, or a > marginally modified 1541 drive ROM to power their units. > > Someone provided me a BlueChip/Amtech drive ROM, and I finally had a > chance to look at it. It's a 16kB ROM, and the e000 looks almost > exactly like the 1541 -05 or -06 ROM. The $c000 portion is radically > different, or at least looks different at first glance. But, given > the minimal changes in the upper half, I burned a copy and > successfully booted a 1541 with it. Thus, I'm wondering if someone > could help me decipher: What is indeed different (of note) in the > $e000 rom? > Why the $c000 rom is so different, and does it need to be that way > (or, can I just replace it with a 1541 $c000 ROM image)? > The files, if folks are interested, are at: > http://www.jbrain.com/incoming/BlueChip/Amtech_BlueChip_ROM.BIN > http://www.jbrain.com/incoming/BlueChip/Amtech_BlueChip_ROM_c000.BIN > http://www.jbrain.com/incoming/BlueChip/Amtech_BlueChip_ROM_e000.BIN > The latter two are just the first split in half. It's the same as the roms of Rapid Access FD148. So, i've disassemled some time ago. Look at http://mhv.bplaced.de/cbmdos/Amtech_BlueChip_ROM.ZIP. Your will find Rapid Access FD148.s and dos2.6_1541_Rev2.s to compare. This rom based von revision 2. I would say that's equal. Only some operation sequence are changed. Any loops are changed to use an index minus/plus one. But both version do the same. MartinReceived on 2020-05-29 22:05:52
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