ICL OPD

[Pr0f]

My bits have arrived to put the power supply / video adaptor board together - so that will be done this weekend - the box is big enough to accommodate a 3.5" floppy - and I found my 5V only TEAC 1M floppy drive so that will be pressed back into service for the OPD.

Next steps:

Test the PSU / VIDEO combo - and check we have life in the old OPD.
Finish modifying my CPU board for the additional ROM decoding - plan is to support the OS and extension for the OS in 2 64K ROMS, leaving one 64K ROM slot free for the ICLBasic in ROM and one 128K area free for either RAM or ROM - jumper selectable.
Test that board in the OPD
Set about doing the Disk interface.

If I still have enthusiasm for it after all that - then do the hardware design for a serial port that can run out of a slot - but I have lots to understand in how devices are handled and how the kernel calls work for the comms calls - since there were already serial designs out there - I am hoping there might be some documentation.

I've also ordered a PBX off ebay - and using some old modems I am hoping to have a play with the telephony capabilities...

[stephen_usher]

And is it possible Stephen, if in your improved/upgraded interface that it could use the more common WD1770 instead of WD1772?

I've no idea what the differences are between the WD1770 and the WD1772. If they're not software compatible then the ROM would have to be re-written.

It looks like Charlie Ingley is working upon a WD1772 replacement board at the moment, by the way.

As for S*BASIC on the OPD, the architecture is very different, even though it uses the QL chipset, and the ICLBASIC has some major differences for handling system resources. From what I've gathered the OPD uses a paged memory management system where programs and data can be fragmented in memory, so any program has to be aware of this and be written accordingly.

[Pr0f]

On the WD1770/WD1772 question -

https://www.bing.com/ck/a?!&&p=a82800f7 ... cyLg&ntb=1

[Chr$]

I read that too on the WD1770/WD1772 re the stepping. I suppose I could just try a WD1770 when I've built the adapter.

Thanks Stephen and Pr0f.

[jobdone]

Whilst I've successfully replaced a 1772 in a Trump card with a 1770, it is hit and miss as to what systems you can swap them in and to be honest the 1770 is getting rarer too. About 3-4 years ago I bought 5 1770's from Ali for just over £10, now I'm lucky to find any and they're now £12+ each. If charlie is making a replacement this or another option would be the way to go.

[Chr$]

I made my interface card today, here it is:

Before I even had a chance to test it I found that my working Merlin Tonto has quietly died in storage and now shows 3 vertical white stripes. Instead of cluttering this thread, here is a new one on that:
viewtopic.php?t=4667

[Chr$]

Looking at that pic I had again of the C1 disk controller and even though there is a sticker on the controller chip, I think it's a WD1770, not a WD1772 as they had a later (85) copyright date, not 82. Anyway, thought that might be of interest. Hopefully I'll have a working OPD soon to try it!

[Chr$]

After some faffing today (dodgy FDD cable) I now have a working C1 clone floppy interface connected to my Merlin Tonto.

A couple of useful observations:

1. It seems to work just as well with the slightly cheaper WD1770-PH controller chip as it does with a WD1772 variant.
2. It also had no issue with a random 1.44mb drive I attached to it jumpered as DS0, formatting as drive A to the normal 720k.

I was able to copy all of the files from the ICL microdrive cartridge wallet (Basic, Demo, Welcome, Help) to a single floppy disk. Imagine how convenient that would have been in the day! What is of course not convenient is the way you have to copy each file manually, naming it from the source and giving it a name to become on the target. Absolute nightmare user interface, but that's by the by.

I did use the ROM version with MS-DOS compatibility but have not yet tried the disk in a DOS machine. Also not tried anything with Gotek and disk images etc yet.

Excellent work Stephen. I'll look forward to making an updated version whenever that comes.

[stephen_usher]

I'm glad you finally got things working.

Note that copying to Goteks running FashFloppy has an issue where the copy fails saying that the destination drive is missing or unusable after it's taken an age changing the FAT setting up the copy and then starting to copy. Saving from applications etc. works fine, so goodness knows what the copy program is doing. As noted, it works fine to a real floppy.

I wish the disk ROM didn't take up so much memory too.

I'll probably get around to working on the Mk.II in February after I've got some real life things out of the way.

[Chr$]

I think I may need a pointer or 2 regarding getting OPD images onto real disks! I found the .IMA image online (attached) and am trying to get that onto a real disk in such a way that the OPD can view the files etc.

I note that Windows/DOS couldn't see any content on a disk I created with the OPD, they just see it as empty, I suspect those CAT files that the OPD creates have something to do with that? The disk interface has the modified DOS friendlier ROM version. I was however able to view the content of a real OPD disk using my QXLII card and could use that method to manually copy files onto an OPD disk, and they worked on the OPD.

I tried SAMdisk yesterday and that didn't work - can't remember the settings. Today I'm attempting to get that image file onto a real disk with Diskette Tool by John Elliott. It allows me (using Win XP) to chose the .IMA file and then chose the real A: drive as target. Tried a few settings there, but it doesn't work, it results in a disk that Win XP can read fine, but the OPD doesn't like it at all.