"The ProDOS system file contains a checksum-like subroutine which returns $0C if a genuine Apple is detected and a $00 otherwise. If a non-Apple is detected ProDOS will just hang and not load in the BASIC.SYSTEM interpreter." A disassembly of this routine from 1-JAN-84 ProDOS: 18 CLC AC 31 26 LDY $2631 B1 0A LDA ($0A),Y 29 DF AND 0$DF 6D 31 26 ADC $2631 8D 31 26 STA $2631 2E 31 26 ROL $2631 C8 INY CC 34 26 CPY $2634 D0 ED BNE $263D 98 TYA 0A ASL 0A ASL 0A ASL 0A ASL A8 TAY 4D 31 26 EOR $2631 69 0B ADC 0$0B D0 03 BNE $2660 A5 0C LDA 0$0C 60 RTS A9 00 LDA 0$00 60 RTS In order for this to work the routine has to be modified so that it always returns $0C. This can be done by replacing the BNE $2660 with two NOP's. The easiest way to do this is with a sector editor. Search for the byte sequence 69 B0 D0 03 since the sequence D0 03 is fairly common. Change D0 03 to EA EA and rewite the sector to disk. ProDOS should now come up and run. Sorry if this is common knowledge.... To defeat the ROM checksum in Prodos: ASL ASL ASL ASL TYA EOR $.... (this address varies from version to version and is therefore omitted) ADC $0B BNE $.... ------+ (The address field of this BNE cmd points to LDA $0C | address of LDA $00 cmd) RTS | LDA $00 <------+ RTS This sequence of code appears at $285B for ProDOS 8 v1.9. All you have to do is to replace BNE instruction with NOPs (two bytes, EA EA) ------------------------begin P8Patch.TXT------------------------- To patch ProDOS to run on a Franklin ACE 1000, 1100, 1200, etc. and probably MANY other clones and workalikes, use a sector editor to search for and replace the following byte sequences in the file "PRODOS": Search for: Replace with: -------------- -------------- 69 0B D0 03 69 0B EA EA AE B3 FB E0 38 A2 EA EA E0 38 This works for all versions of ProDOS up to v1.9. It may also work with v2.x if your Franklin or other clone works properly with a 65c02 or 65c802 CPU. 22 April 1994 John D. Baker ->A TransWarp'802'd Apple //e CardZ180 Z-System nut // Internet: jdb8042@tamuts.tamu.edu, @blkbox.com, jdbaker@taronga.com BBS: JOHN BAKER on PIC of the Mid-Town [(713) 961-5817] 1:106/31, Z-Node #45 [(713) 937-8886], The Vector Board [(716) 544-1863] Bibliography: Trueman, Doug., (May 1986)., ***** NEW PATCHES *****., _The Clone ACE_., Vol. $0C., A.S.C.I.I., Tecumseh, MO. --------------------------end P8PATCH.TXT------------------------