Supersoft BASIC 2+4

  • The BASIC 2+4 board from Supersoft is a daughterboard that provides software-selectable BASIC 2.0 and BASIC 4.0. The machine boots to BASIC 4. Entering “SYS 65520“ switches to BASIC 2 and back again.

    The board is designed for older PET machines. Compatible PETs have the BASIC ROMs in sockets UD6-9 and dynamic RAM. To install the BASIC 2+4, the BASIC ROMs are removed and the BASIC 2+4 is installed into one of those sockets. A cable is then connected from the BASIC 2+4 to the J9 expansion header.


    Top Side
    Top Side: Parts Placement
    Top Side: EPROMs Removed
    Bottom Side

    The board has no reference designators. The “B4” and “B2” EPROMs are 27128s (16 KB). The “004” EPROM is a 2764 (8 KB). The other chips are a 74LS174 (close to the “B2” EPROM) and a 74LS139.

    Note the photo with the EPROMs removed. The instructions call it the “BASIC 2+4 BOARD” but the board has “Microport Issue 2.0” written on it under the “B2” EPROM. The board also has two space for 28-pin chips that are unpopulated and has various pads on both sides that are for reconfiguration. It’s likely this same circuit board was used for other products.


    B4.BIN – 27128 (16 KB), Sticker reads “B4”
    B2.BIN – 27128 (16 KB), Sticker reads “B2”
    004.BIN – 2764 (8 KB), Sticker reads “004”