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Very interesting! I had never seen those ads. By the time I heard about OSI, they had just introduced the 500 board, although I remember their SSJ was full of 400-series references. I find these old Byte magazines just as fascinating now as I did back then, although for different reasons. What's mos...

Latest update: the board is on its way from Hong Kong. . .

Glad to hear it! I'm also glad you have documented it all here, for others to learn from. I am hoping the disk will work. Keep us all posted!

Dave

A short description of the ROM/EPROM page remapping scheme which allows a single 2K ROM to store 8 256-byte code blocks to configure the OSI CPUs for ROM BASIC, disk boot, ASCII vs Polled Keyboard, serial vs video-based monitors, while avoiding stepping on the serial port at FC00. The ROM mapper is ...

Hi Dave, Thanks for the tip. Unfortunately I don't have Basic in ROM. If you recall from another thread I have been trying to get Basic to load from the Serial port, but I need to get the SYN600 ROM to load to C/W/M menu before I can do that, and I was going to attack that project after finishing t...

It's probably a good plan to just start replacing chips. Then, you can start putting chips back until it fails, to find out which one was bad. That way you also can reserve most of the new chips to fix something else. You are right that it could be a socket problem. Even if it isn't you may want to ...

I moved my reply from the Files. . . Forum, since it's really more applicable here. That might give you a starting point Also, if you try the obvious and are still stymied, then do you by any chance have BASIC in ROM available? Or, can you map an 8K block of RAM to A000? The reason I ask is, if you ...

[Moved from "Files. . .Looking for OSI 542C Keyboard Schematic "] Merry Christmas! I only have the 542 and 542B schematics. I checked the SAMS manual, and it appears to only have the "B" revision. However, the only difference between the "B" and "C" models, according to Mark's OSI page is the additi...

That's really neat. Would you care to post a little tutorial on changing the bearings, and can you show which nut was overtightened? I imagine many of these drives may have end-of-life bearings.

Hi Philip, The 505 card has ROM-segment remapping logic, just like the 502 card, to map any 256 byte block in the ROM to FE00, FD00, and FF00. So theoretically, you could put the blocks in any order, and set the jumpers accordingly. However, if the ROM in the machine works, you can use it; default s...