Search found 429 matches

by stephen_usher
Thu Jan 11, 2024 8:12 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

The biggest problem is not so much getting the programs as making Microdrive carts which can be read by the OPD.
by stephen_usher
Wed Jan 10, 2024 9:48 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

The issue with BASIC is that it doesn't fit in the 32K ROM slot size. The Telestore hacked things and fitted it in two 32K ROM slots. RAM expansions have to pretend to be ROMs in the ROMpack and then have code which hacks the OS into ignoring the "BAD ROMs" and telling where the extra RAM ...
by stephen_usher
Wed Jan 10, 2024 9:38 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

The interface maps the floppies to the left and right Microdrives. As far as the system and applications are concerned it still has only the two Microdrives and nothing else.
by stephen_usher
Wed Jan 10, 2024 7:35 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

I've no idea how to access it from BASIC at the moment as I don't have a fully working version of BASIC as that comes on Microdrive and isn't built in. As for the design being published. I'll work on a Mk.II which will fix a few things such as the connector having to be on the "wrong" side...
by stephen_usher
Wed Jan 10, 2024 7:13 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

David Warne and Rich Mellor got the Computer One floppy interface ROM image to me today...

Wrote it to EEPROM, set things up, switched on and...

IMG_3533.jpeg

The interface only goes and works first time!

IMG_3532.jpeg
by stephen_usher
Sun Jan 07, 2024 2:44 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

Mine only has three MOSFETs.
by stephen_usher
Sat Jan 06, 2024 10:02 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

Oh, OK.I wonder why my system runs without that signal being high. Everything runs except the SRAM. Bad MOSFET maybe?
by stephen_usher
Sat Jan 06, 2024 7:39 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

But the "shutdown" pin doesn't go anywhere other than to one transistor which controls the SRAM. I can't find it going anywhere else. You'd have thought it would have kept the machine from powering up at all until it was high, but it doesn't.
by stephen_usher
Sat Jan 06, 2024 1:37 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

I've been having issues with my OPD not starting up and giving the 5 bar error, which according to this document is "SRAM fault" OPD-Boot-Diagnostics.jpg This morning I traced the issue to /CE1 never going low. Chased the line way over to the left of the board to a transistor which inverte...
by stephen_usher
Wed Jan 03, 2024 8:59 pm
Forum: Hardware
Topic: ICL OPD / Merlin Tonto Issues
Replies: 1
Views: 2597

Re: ICL OPD / Merlin Tonto Issues

Looks like 6 bars is DRAM and not SRAM fault from that document.


OPD-Errors.JPG