Ohio Scientific

djg at pdp8.net djg at pdp8.net
Fri Jan 25 11:16:48 CST 2008


I'm working on getting my Ohio Scientific Challenger II running.
The system is a 505 CPU (first rev that doesn't match schematics online), 
535 memory 48k (no schematics online I have found), 540B video card 
with color and dual 8" floppy.  This machine was modified with a switch so 
I can use either the video board or a serial terminal.
Its pretty close to the system I first used in high school.

I think I have the computer working but would like to run a memory test.
Does anyone know of one available that I could load in through the
monitor? Or do I need to see how much 6502 I can remember from 25 years
ago? 

The video card generates the first line right after end of vertical
blank so all my monitors cut off most of the first line. Is this normal?

Next is moving on to the the 8" floppies. After I get them working I want
to dump all the disks I have.
I found at osiweb a program to dump floppies but it was for 5 1/4".
Does anybody know of one that will dump the 8"? Perferably in a format
that an emulator can use so I can verify the dumped disks are good.




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