On 5/17/2019 8:49 AM, Martin Hoffmann-Vetter wrote: > 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. > > Martin > > Thanks. I was attempting to disassemble it last night, but it was going to take some cleanup. Given Pete's response about putting a JD ROM in and the thing refusing to work, does anyone on list have the drive and would be willing to test? I've got some folks wanting a JD ROM, and I'd rather just suggest a 1541C ROM if it would work. Jim -- Jim Brain brain_at_jbrain.com www.jbrain.comReceived on 2020-05-29 22:05:19
Archive generated by hypermail 2.3.0.