alexhagn@neabbs.UUCP (ALEXANDER HAGEN) (07/11/90)
While exploring my Amiga bridgeboard, I found a bug in the Janus 2.0 system
software (Handler 2.63, Library 33.1). Since I can program in 8088
Assembler as well, I decided to fix it myself.
The bug is located in the JFreeMem routine in the PC.Boot file.
What's wrong? When returning allocated memory, the JFreeMem function adds
the wrong memory locations together. Also, the wrong byte is unlocked,
causing data destruction elsewhere in Janus memory! Any other call to the
janus mem alloc and free functions will lock up the bridgeboard. Only an
Amiga-reset will fix this - unless you know what byte to change :-)
To find out wether your bridgeboard contains the bug, enter the following
lines on the MS-DOS side:
A> debug
-a 0100
1436:0100 mov ax,0202
1436:0103 mov bx,0100
1436:0106 int 0b
1436:0108 push bx
1436:0109 mov ax,0202
1436:010C mov bx,0100
1436:010F int 0b
1436:0111 mov ax,0302
1436:0114 int 0b
1436:0116 pop bx
1436:0117 mov ax,0302
1436:011A int 0b
1436:011C nop
1436:011D
-g=0100 011c
-q
If the bridgeboard does not return to the dos prompt, your system software
contains the bug. In that case, follow the steps below:
1) Reset the Amiga
2) Run the BASIC program, listed below
3) Reset the Amiga again
REM Janus 2.0 Bug fix
REM Copyright (c) 1990 by drs. A.D. Hagen
CLEAR,50000&
REM Checking data for typing errors
check&=0
FOR i=0 TO 100
READ num
check&=check&+num
NEXT i
IF check&<>700730& THEN PRINT "Data contains error!!!":STOP
REM Removing bug
RESTORE
NAME ":pc/system/pc.boot" AS ":pc/system/pc.boot.old"
OPEN ":pc/system/pc.boot.old" FOR INPUT AS #1 LEN=4096
OPEN ":pc/system/PC.Boot" FOR OUTPUT AS #2 LEN=4096
PRINT #2,INPUT$(1168,#1);
a$=INPUT$(202,#1)
FOR i=0 TO 100
READ num:IF num<0 THEN num=num+65536&
msb=INT(num/256):lsb=num-256*msb
PRINT #2,CHR$(msb);CHR$(lsb);
NEXT i
PRINT #2,INPUT$(10918,#1);
CLOSE #1,#2
DATA &H1E83,&HEB04,&H2E8E,&H06EE,&H218C,&HC18E,&HD9BF,&H0200
DATA &H3C01,&H7407,&H3C02,&H75D7,&HBF10,&H0026,&H3B5D,&H0A73
DATA &HCEF9,&HF026,&HD015,&H7304,&H9090,&HEBF5,&H8D75,&H0857
DATA &H0656,&H068B,&H7508,&H8E5D,&H068B,&H4F02,&H2601,&H4D0C
DATA &HEB49,&H222A,&H2A2A,&H2042,&H7567,&H7320,&H6669,&H7865
DATA &H6420,&H6279,&H2064,&H7273,&H2E20,&H412E,&H442E,&H2048
DATA &H6167,&H656E,&H2028,&H5555,&H4350,&H3A20,&H616C,&H6578
DATA &H6861,&H676E,&H406E,&H6561,&H6262,&H732E,&H7575,&H6370
DATA &H2920,&H2A2A,&H2A58,&H5856,&H1E8B,&H3439,&HDE72,&HF607
DATA &H5F89,&H3726,&H891D,&H268B,&H5502,&H89D0,&H01FA,&H39DA
DATA &H750E,&H2601,&HC826,&H8945,&H028B,&H0726,&H8905,&H89FB
DATA &H89D8,&H01C8,&H39F0,&H750A,&H8B44,&H0201,&H4702,&H8B04
DATA &H8907,&HB000,&H075F,&H26C6,&H057F
END
Hope this helps...
-----------------------------------------------------------------------
_ Alexander Hagen | PRIV MSGS IN DUTCH, GERMAN OR ENGLISH
_/_\__ Newtonstraat 20 |
````-o--o- 4532 KH Terneuzen | UUCP alexhagn@neabbs.UUCP
The Netherlands | Fido 2:285/403.2
------THE-FIRST-AND-ONLY-UNREGISTERED-AMIGA-BRIDGEBOARD-DEVELOPER------