[BBC-Micro] Issue 4 will not accept a 1770

Mark Haysman jumbos.bazzar at btopenworld.com
Fri Jun 5 20:28:22 BST 2009


>>  I'm certain the ROM's are fine, as I have a functioning WE 1770 board
>> (the WE is an issue 1) in an Issue 7 B, that's the machine I
>> used to test the newer components in too.
>
> Have you checked the machine is 'seeing' the ROM? Does another ROM work
> in that socket? I've had one iss4 machine with very dodgy ROM sockets in
> the past.
>
> While 1770DFS doesn't start up if it can't see it's controller, it
> wouldn't be too hard to write a bit of BASIC read the first few bytes
> from the ROM to check it is actually there.
>
> I'd also check the /CS line on the FDC  is being driven correctly (ie.
> the address decoding is working)  tho this really needs a scope.

You can check a ROM is being seen by forcing it to do a language startup, if 
the ROM is in the socket next to the OS for instance, a

*FX142,12

Should give a short message identifying the ROM, although it will crash the 
machine. 13, 14 and 15 are the next ones alog.

As for the Watford DDFSs, V1.54T is compatible with the Acorn boards (and 
mine), and uses the DDB3 PCB, all (?) earlier versions use the DDB2 board, 
and have things located differently.

Mark. 





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