Re: 1541 clone help needed

On 2019-05-17 21:43, Jim Brain wrote:

> 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.com [1]

Hi Jim, 

I went back and found my Lemon64 post about it, and it was an "Enhancer
2000" drive that I had that would not work with the 1541 Jiffy ROMs, not
the Blue Chip. A lot of those drives were clones of each other, though,
so who knows. 

It's actually pretty crazy what it does. The drive boots, responds to
IEC commands, everything. When you try to load something, it flips out
and acts like the disk is full of errors, chattering and carrying on.
With the original ROM back in, everything loads fine. 

I expected maybe a byte-swapped ROM or something, but not the case here.


-- 
--
Pete Rittwage 

Links:
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