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My pleasure. That's great news. Looking back at the schematic, I see that the default jumpering actually places the banks at $2000-$3FFF, $4000-$5FFF, and $6000-$7fff. This was probably based on the assumption that a 502 board with 8K was present. For your 505 system, the 527 jumpering would be diff...

Hi Phil, The 2114 chips are organized as 1K x 4 bits, so two chips form each 1K block, each chip spanning the entire 1K. The 1K boundaries span xx00-xx3F, xx40-xx7F, xx80-xxBF, and xxC0-xxFF. So all the errors are in a single 1K block, from 4400-44FF. The RAM on the 527 is organized as 3 x 8K banks,...

Sounds like a good plan. Don't forget, you will still need to set the jumpers on the 527 board to have a place to put the BASIC interpreter. Since you have a 505 board that already has a floppy interface and boot code, perhaps it would be no harder for you to locate a 3.5" internal floppy, build up ...

Hi Frank, Thank you for documenting that. I have added your mod to the tips/tricks section of the website, along with a transcript of this thread as a kind of read-me file. Does the consolidated BASIC image include the garbage collection fix? If not, I can provide a fixed ROM image. Best regards, Dave

I think the adapter would work fine. But then again, you could just move the jumper going to pin 20 of U2D from pin 4 of U4E to pin 2 of U4E. I suppose it's a good policy not to fiddle with something that is working. For me, though, the whole appeal of the OSI, as opposed to an Apple, was always tha...

The circuit is a little odd, in that the ROM doesn't just map to the address space. It's purpose is to make sure that the computer finds the keyboard routine at $FD00, the 65V monitor at $FE00, and the boot routine at $FF00. To save money, OSI used the same BASIC ROMs and monitor ROMs throughout the...

Did you check the jumpering of your 527 board? Don't forget that to run BASIC-in-ROM, you need a place to put the BASIC at $A000, and also RAM at $0000. The three 8K blocks on the 527 can be assigned on any 8K boundaries, so you could put one at $A000, and the others at $0000 and $2000, but I doubt ...

It's a home-made 8" floppy interface board. You may want to keep it just for fun, in case you ever come across an 8" drive.

Dave

Now that the main machine is fixed (although I'm still having issues with the other 24k board) I'm going to concentrate on the cosmetic issues. First I have to get the case sandblasted, then I'm going to patch all the holes with HTS 2000 (amazing stuff) http://www.youtube.com/watch?v=N-cv3R4fWZc an...

Thread moved to Discussion & Projects. That's great Phil! I remember that auction! I also bought a couple of boards from the same seller. You got a nice machine there. Fixing the other RAM board should be pretty straightforward. Have you checked the power rails on the second 527 board? If not, then ...