Below is the cross reference of part numbers you asked for. I have written it as a text file since writing an e-mail this long without errors would be very difficult (at least for me). petbasic-4 [ 901465-23 + 901465-20 + 901465-21 ] petbasic-4-unpatched [ 901465-19 ] petchars [ 901447-10 ] petedit-2-n [ 901447-24; also the same as 6540-024 ] petedit-4-40-b-noCRTC [ 901474-02 ] petedit-4-40-n-50Hz-reconstruc [ 901498-01 ] petedit-4-40-n-60Hz [ 901499-01 ] petedit-4-40-n-noCRTC [ 901447-29 ] petedit-4-80-b-50Hz [ 901474-04 ] petedit-4-80-b-60hz [ 901499-01 ] petkernel-4 [901465-22] petrom-1 [ 901447-09 + 901447-02 + 901447-03 + 901447-04 + 901447-05 + 2K of fill + 901447-06 + 901447-07 also the same as 901439-09 + 901439-05 + 901439-02 + 901439-06 + 901439-03 + 2K of fill + 901439-04 + 901439-07 ] petrom-2-b [ 901465-01 + 901456-02 + 901474-01 + 2K of fill + 901465-03 also the same as 6540-020 + 6540-021 + 6540-022 + 6540-023 + no equivalent + 2K of fill + 6540-025 + 6540-026] The table below, from the information file in the PET section, can be interpreted as follows: The three digits before the decimal point are the 6540 suffix. The digits after the decimal point are a date code. For instance, 018.4378A is a 6540-018 made the 43rd week of 1978 > $F800-FFFF 018.4378A > $D800-DFFF 014.4278A > $C800-CFFF 012.4278A > $F000-F7FF 016.4478A > $E000-E7FF 015.4478A > $D000-D7FF 013.4478A > $C000-C7FF 019.1878A The two tables below, from the same file, present a problem. I can vouch for the ROM numbers in the first table since I have a computer with those ROMs in it. I also have service information on that machine from before the upgrade was issued. This information uses the part numbers in the first table as the numbers for the ROMs in the first table. Unless Commodore issued two different sets of ROMs using the same part number, the part numbers in the second table are wrong. > Location ROM Part Number > ------------------------------ > H1 6540-019 901439-09 > H2 6540-013 901439-02 > H3 6540-015 901439-03 > H4 6540-016 901439-04 > H5 6540-012 901439-05 > H6 6540-014 901439-06 > H7 6540-018 901439-07 > A2 6540-010 901439-08 [character generator] As noted above, the following table has problems. The part numbers cannot be right. I have other documentation that confirms that the ROM numbers below are for Basic 2, the same as that in the 2001-N. Commodore's replacement parts list uses the part numbers according to the table below, however that list is notoriously unreliable and should not be depended upon without other confirmation. > Location ROM Part Number > ------------------------------ > H1 6540-020 901439-09 > H2 6540-022 901439-02 > H3 6540-024 901439-03 > H4 6540-025 901439-04 > H5 6540-021 901439-05 > H6 6540-023 901439-06 > H7 6540-026 901439-07