Oric Microdisc Issue

[Simonh1]

Hi guys, I have a strange issue with a Microdisc controller in that it seems to work fine but will not handover to the OS after booting, you get the normal 'Insert System Disc' message and after inserting a valid disc (tested on another machine and controller) it loads but after the bytes free message locks up, I have been in conversation with Mickael who suggested trying Blakes 7 as that boots differently which I have done and that locks up too on the flashing disc logo, I have changed the 1793, 9216 and Eprom from the working controller to no avail, I have swapped leads, PSU's and tried a Gotek and a 3.5" floppy too, does anyone have a block diagram of the boot sequence so I can follow the logic through and test the associated IC's, I don't really want to start swapping out all the logic chips unless I really have to.

Many thanks in advance

[Dbug]

Yeah so from what I saw, when trying Blake's 7 sometimes it freezes before even showing the floppy disk icon, sometimes the icon is shown completely, sometimes it's half corrupted, etc...

What that mean is that at least some of the time the boot sector loads, and the loader loads, and it goes far enough to show the disk access icon, so most probably most of the stuff work... but unreliably! Which made me think of the Jasmin issue: Could it simply be a problem of bad cable, bad shielding, electronic noise, etc... randomly corrupting data on the way from the floppy to the Oric?

[iss]

Indeed, bad cable and/or connectors are always the first suspects.
There's no such 'block diagram' of boot sequence - it's actually simple - FDC ROM loads track0/sector1 in RAM and jums to it, then depending on OS (i.e. Sedoric, FloppyBuilder, etc) boot code loads next sectors...
It's worth to try with AmpliBus and/or shorter cable. Also for first tests use Gotek to eliminate all possible issues with real floppy drives and disks.

[Simonh1]

I have a Cumulubus would that work?? and if so would it need power??

[iss]

Unfortunately, no. Cumulus bus is different.

[Simonh1]

I thought I may as well try and start replacing chips, after looking at the schematic for some time I decided to start with IC3 an LS245 as it seems to handle most of the addresses, et voila it now works first time every time, however, it still wont load Blakes 7 from the Gotek, it loads Sedoric, OricDos, Space 1999, Pulsoids etc???

Think I will change IC2, 5 & 14 too.

[iss]

Post some pics of your setup, maybe they can help.

[Simonh1]

I could but it’s not really a setup, I have several Atmos and Oric 1’s, a Telestrat, 4 Microdisc, a Cumana, a Jasmin and a Byte Drive 500, I also have all the add ons you can get like Loki etc. the controller I’m working on is a C type Microdisc, I have another 2 that also need repair and will get to them in due course, all that’s on the bench is a gotek, the controller and an Atmos, I’m using my bench psu.
I collect and repair 8 bit machines as a hobby.

[Chema]

I thought I may as well try and start replacing chips, after looking at the schematic for some time I decided to start with IC3 an LS245 as it seems to handle most of the addresses, et voila it now works first time every time, however, it still wont load Blakes 7 from the Gotek, it loads Sedoric, OricDos, Space 1999, Pulsoids etc???

Think I will change IC2, 5 & 14 too.

I'm afraid I cannot help with hardware, but, from our last tests with the Jasmin controller, it seems to me that Blake's 7 may hang only when noise in the cable from the controller to the Oric produce errors unrelated with the actual floppy data reading (thus, not being signaled as such from the FDC chip) or strange delays. In other cases, the game routines should retry indefinitely.

Why not put aluminum foil around the cable as mininaller did and see if it works in your case too?

I am surprised that Sedoric disks work, but not Blake's 7, but they may use IRQ driven routines which may be more reliable in some of those cases....

[Simonh1]

Thanks for all your input guys, finally got it running 100% by changing some of the logic chips, now to repair the other 2 I have that don't work at all...

[Chema]

Thanks for all your input guys, finally got it running 100% by changing some of the logic chips, now to repair the other 2 I have that don't work at all...

Great! Another one saved!