1541 clone help needed

From: Jim Brain <brain_at_jbrain.com>
Date: Thu, 16 May 2019 20:48:02 -0500
Message-ID: <bfdac072-5b05-95cb-da2a-54c1cd8d3b51_at_jbrain.com>
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.

Jim

-- 
Jim Brain
brain_at_jbrain.com
www.jbrain.com
Received on 2020-05-29 22:06:40

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