REU jumpers and function ROMs
Posted: Thu Mar 21, 2013 10:30 pm
I am searching for information and experience about using the function ROM socket in a CBM REU with a C-128. I own a 1750. I soldered in a 28-pin chip socket at the bare spot on the board and have been experimenting with it for function ROM use with my C-128D. So far I can’t get a function ROM to work in the REU socket. The same ROM works in the internal socket. (I made sure to disable the internal ROM before trying the external.)
Here are the notes I have on the jumpers inside the REU:
Has anyone else used the external function ROM socket in the REU successfully? Any info would be most appreciated.
Thanks,
--Kent
Here are the notes I have on the jumpers inside the REU:
- J1 = how much RAM / how dense. I believe it’s cut for 1700/1750 and connected for 1764.
- J2 = How big of a function ROM for socket—connect one direction for 16K, the other for 32K
- J3 – J5 = ROMH, ROML, and ROMHL. I think this indicates where in the memory map the ROM will appear:
- 16k ROM at $8000 thru $BFFF (ROML)
- 16k ROM at $C000 thru $FFFF (ROMH)
- 32k ROM at $8000 thru $FFFF (ROMHL)
Has anyone else used the external function ROM socket in the REU successfully? Any info would be most appreciated.
Thanks,
--Kent