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====== RBBS/BYE and CP/M ======

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  * //To//: N8VEM-Post <<n8...@googlegroups.com>>
  * //Subject//: RBBS/BYE and CP/M
  * //From//: "Richard A. Cini" <<rc...@optonline.net>>
  * //Date//: Tue, 23 Jun 2009 19:55:17 -0400
  * //Authentication-results//: gmr-mx.google.com; spf=neutral (google.com: 167.206.4.196 is neither permitted nor denied by best guess record for domain of <rc...@optonline.net>) smtp.mail=<rc...@optonline.net>
  * //Thread-index//: Acn0Xg7Z9NKqmCdG00m/UadCCuELGw==
  * //Thread-topic//: RBBS/BYE and CP/M
  * //User-agent//: Microsoft-Entourage/12.19.0.090516

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Title: **RBBS/BYE and CP/M**

All:\\
\\
    Although I have more testing to do, I believe that I’ve solved the problem. BYE and RBBS now work after I looked into Max’s suggestion about the combined CP/M and CBIOS, which also revealed an error introduced when we patched CP/M for the user-area prompt. Be sure to verify that CCP, BDOS and the CBIOS origination addresses match or otherwise reconcile to what is expected for the related MSIZE as specified in the modification guide or the “Programmer’s\\
CP/M Handbook”. When the user-prompt compilation switch is used, you need to add 3 to the related offsets in order for the addresses to line-up properly:\\
\\
0046   0000             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%*\\
0047   0000             ; "BIAS" IS ADDRESS OFFSET FROM 3400H FOR MEMORY SYSTEMS\\
0048   0000             ; GREATER THAN 16K.\\
0049   0000             ; ONLY VALID FOR CP/M 2.2 SYSTEMS    \\
0050   0000             BIAS    .EQU    (MSIZE-20)*1024                0A000H\\
0051   0000             CCP     .EQU    3400h+BIAS    ; CCP ENTRY POINT     0D400H\\
0052   0000~                .IF    CONDUSRPATCH       ; budget for extra 3 bytes for JP\\
0053   0000~            BDOS    .EQU    CCP+800h+6    ; BDOS ENTRY POINT    0DC06H\\
0054   0000~            CBIOS   .EQU    CCP+1600h     ; CBIOS jump table    0EA00H\\
0055   0000                 .ELSE\\
0056   0000             BDOS    .EQU    CCP+800h+9    ; BDOS ENTRY POINT    0DC09H\\
0057   0000             CBIOS   .EQU    CCP+1600h+3   ; CBIOS jump table    0EA03H\\
0058   0000                 .ENDIF\\
0059   0000             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%*\\
\\
    The “800h+6” is normal per the code in the alteration guide. Notice the “else” clause where the offsets are three bytes greater — that accounts for the “JP AAAA” for the prompt patch.\\
\\
    I remembered from my IMSAI that MBASIC relied on the CBIOS jump table being just that — a table of jumps — and nothing else. The current N8VEM table had a minor short cut relating to the punch, reader, and list devices. I corrected these so that the table is a true jump table.\\
\\
    Second, I made each entry an internal jump. For example (only first two shown) and modified any loop routines so that they didn’t loop to the jump table and back.\\
\\
3922   EA03             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%\\
3923   EA03             ;*\\
3924   EA03             ;*        B I O S   J U M P   T A B L E\\
3925   EA03             ;*\\
3926   EA03             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%\\
3927   EA03             ;\\
3928   EA03             ; JUMP VECTOR FOR INDIVIDUAL SUBROUTINES - these must be\\
3929   EA03             ; JMP/JP instructions and nothing else.\\
3930   EA03             ;\\
3931   EA03 C3 F0 EA    BOOT:     JP    IBOOT        ; COLD START\\
3932   EA06 C3 0B EB    WBOOT:    JP    IWBOOT       ; WARM START\\
\\
    Note that the address of EA03 matches the math in the “CBIOS” equate above. All of the routines in the CBIOS are now “I” plus something to indicate that they are “internal” routines. The location reference name is the “real” name expected by CP/M.\\
\\
    For completeness, here is the BDOS entry showing the matching entry address:\\
\\
1319   DC03             ;   NOTE THAT THE FOLLOWING SIX BYTES MUST MATCH THOSE AT\\
1320   DC03             ; (PATTRN1) OR CP/M WILL HALT. WHY?\\
1321   DC03             ;\\
1322   DC03 001600000000PATTRN2:.DB 0,22,0,0,0,0    ; (* SERIAL NUMBER BYTES *).\\
1323   DC09             ;\\
1324   DC09             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%\\
1325   DC09             ;*\\
1326   DC09             ;*                    B D O S   E N T R Y\\
1327   DC09             ;*\\
1328   DC09             ;%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%%%**%%\\
1329   DC09             ;\\
1330   DC09 C3 14 DC    FBASE:    JP    FBASE1\\
\\
    I have to pull together a web page about this but I think that these changes will reduce future compatibility problems and make the ROM distribution closer to standard CP/M.\\
\\
    The only RBBS problem I have to trace down is an anomaly with the menus.\\
\\
Rich\\
\\
--\\
Rich Cini\\
Collector of Classic Computers\\
Build Master and lead engineer, Altair32 Emulator\\
http://www.altair32.com\\
http://www.classiccmp.org/cini\\

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      * //From:// "James Moxham (Dr_Acula)" <mox...@internode.on.net>

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