Kevin Williams
Experienced Member
Hello Everyone,
I have a Tandy Model II working like a champ, and I was lucky enough to get ahold of an 8Mhz 68k board, and two 256k memory boards. This board seems to be the one used in a Tandy 6000, and minus the dual floppies and internal hard drive, I'm guessing this machine should basically be a Tandy 6000. After some reading, it seems the Z80 CPU board is pretty much the same for all of the machines in the series. As such, I expected that this would work fine. However, the speed of the original 68k board being 6mhz makes me wonder which CTC was used on the Model II board vs the 6000. I know each Z80 is running @ 4mhz. The 6000 schematics shows a 2mhz signal being provided to the CTC and the Model II board also shows the same. The only 68k code I can run it seems is the diag disk which was posted to the archive, and it runs just fine even in 68k mode. However one of the interrupt tests fails, which is the 68000 Interrupt to Z80 which says "can't verify Z80 CTC count".
So, I'm left scratching my head! I guess I'm wondering if anyone out there has a real 6000, and what happens when this test is run? Also, this seems bad, as I'm sure being able to read this value will be critical, in-particular for HW interrupt functions which would probably be an issue running Xenix or other 68k based OS's. Maybe it's not an issue? Not sure, but every other test run passes like a champ! I didn't compare everything in the schematics, but I would guess all of the address and data lines are plumbed the same way, so speed seems like it would be the only other factor. I don't expect the CTC is faulty, as I'm sure booting any OS in Z80 mode would fail, not to mention some of the Z80 tests should fail. They all pass as they should.
Anyway, I'm guessing there isn't really a lot that I can do about this. I just couldn't find that anyone else has tried this combo before and thought it wouldn't hurt to give it a try. I did replace the power supply, by the way, so there is plenty of amperage to run the boards. I even removed the HANS-01 to make sure it wasn't somehow interfering but the condition remains the same. I also tried with only one memory board, no luck there either. There really isn't anything else I can remove and still run the test, so I'm likely at a dead-end, but I was hoping someone out there had a thought.
Thanks!
-Kevin
I have a Tandy Model II working like a champ, and I was lucky enough to get ahold of an 8Mhz 68k board, and two 256k memory boards. This board seems to be the one used in a Tandy 6000, and minus the dual floppies and internal hard drive, I'm guessing this machine should basically be a Tandy 6000. After some reading, it seems the Z80 CPU board is pretty much the same for all of the machines in the series. As such, I expected that this would work fine. However, the speed of the original 68k board being 6mhz makes me wonder which CTC was used on the Model II board vs the 6000. I know each Z80 is running @ 4mhz. The 6000 schematics shows a 2mhz signal being provided to the CTC and the Model II board also shows the same. The only 68k code I can run it seems is the diag disk which was posted to the archive, and it runs just fine even in 68k mode. However one of the interrupt tests fails, which is the 68000 Interrupt to Z80 which says "can't verify Z80 CTC count".
So, I'm left scratching my head! I guess I'm wondering if anyone out there has a real 6000, and what happens when this test is run? Also, this seems bad, as I'm sure being able to read this value will be critical, in-particular for HW interrupt functions which would probably be an issue running Xenix or other 68k based OS's. Maybe it's not an issue? Not sure, but every other test run passes like a champ! I didn't compare everything in the schematics, but I would guess all of the address and data lines are plumbed the same way, so speed seems like it would be the only other factor. I don't expect the CTC is faulty, as I'm sure booting any OS in Z80 mode would fail, not to mention some of the Z80 tests should fail. They all pass as they should.
Anyway, I'm guessing there isn't really a lot that I can do about this. I just couldn't find that anyone else has tried this combo before and thought it wouldn't hurt to give it a try. I did replace the power supply, by the way, so there is plenty of amperage to run the boards. I even removed the HANS-01 to make sure it wasn't somehow interfering but the condition remains the same. I also tried with only one memory board, no luck there either. There really isn't anything else I can remove and still run the test, so I'm likely at a dead-end, but I was hoping someone out there had a thought.
Thanks!
-Kevin
I'm learning more still, and still have a few Tandy's in my collection.