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Coco SDC & OS9 Boot - Solved

Posted: Wed Jan 20, 2021 12:12 am
by dublevay
Some of you will be aware of the issues that have been experienced with the Coco SDC and OS9. It has often meant mounting the VDK in DOSplus and then BANKing across to another DOS prior to BOOTing the image.

Finally, the root cause of that has been identified, and I have prototype boards which demonstrate this.

This video shows a DragonPlus-endowed machine booting OS9 from a CocoSDC before the fix and after the fix.

I hope to have the adapter boards available for sale soon.

Re: Coco SDC & OS9 Boot - Solved

Posted: Sun Apr 25, 2021 10:49 am
by MaestroSoftware
Hello. I recently dug up my Dragon 64 with Dragonplus. I have to repair the Dragonplus monitor connection, so I don't know yet if it still works, but the Dragon itself seems to work.
I'm afraid I lost ALL my floppy disks (but I have vdk images of many of them), so I thought I would buy a CocoSDC from The Zippster Zone. Is it easy to solve the reliability issue with OS/9 ? (I really suck at electronics, I'm afraid). Or should I maybe try and find a DragonDrive or DragonMMC instead if I want to get back to OS9 L1 on my D64 with Dragonplus?
Thank you for your help

Re: Coco SDC & OS9 Boot - Solved

Posted: Tue Apr 27, 2021 6:50 pm
by dublevay
There's two ways to solve the CocoSDC issues with the DragonPlus (or OS9 in general).

First would be simply to BANK to another DOS version before booting.

So you'd start in DOSPLUS. Then...

BANK 3 (I have Eurohard DOS in ROM bank 3 of the Coco SDC)
The machine cold boots into Eurohard DOS with your VDK still attached.

Second way is to use the pull-up solution, as detailed here: ... resistors/