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pcjs/disks/pc/unix/microport/system-v/2.3
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Repository files (latest commit first)
Filename Latest commit message Latest commit date
Jeff Parsons d97c773613 Some task-switching fixes
2015-05-17 11:58:36 -07:00
..
manifest.xml More 80286 testing 2015-05-15 09:08:42 -07:00
README.md Some task-switching fixes 2015-05-17 11:58:36 -07:00
SYSTEMV23-DISK01.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK02.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK03.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK04.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK05.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK06.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK07.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK08.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK09.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK10.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK11.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK12.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK13.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK14.json More 80286 testing 2015-05-15 09:08:42 -07:00
SYSTEMV23-DISK15.json More 80286 testing 2015-05-15 09:08:42 -07:00

README.md

Debugging Notes

The boot sector contains the following code:

0000:7C3E B003 MOV AL,03 0000:7C40 B200 MOV DL,00 0000:7C42 B417 MOV AH,17 0000:7C44 CD13 INT 13 0000:7C46 72B8 JC 7C00

For BIOSes that don't support INT 0x13, AH function 0x17, patch the JC with two NOPs; eg:

e 0:7c46 90 90

After booting, the following code is executed:

12E8:01D3 52 PUSH DX ;history=5 12E8:01D4 51 PUSH CX ;history=4 12E8:01D5 2BC9 SUB CX,CX ;history=3 12E8:01D7 BA6400 MOV DX,0064 ;history=2 12E8:01DA ED IN AX,DX ;history=1

For virtual machines that don't support word I/O to port 0x64, patch IN AX,DX with IN AL,DX; eg:

e 12e8:1da ec

Here's where the first task switch (far jump using a TSS selector) occurs:

AX=02F0 BX=0008 CX=0000 DX=0000 SP=037E BP=037E SI=1852 DI=0000 
SS=0044[001800,07FF] DS=0228[009E00,851B] ES=0220[001000,8DFB] A20=ON 
CS=0200[012320,FFFD] LD=02E0[002000,01FF] GD=[001006,072F] ID=[0053E2,07FF] 
TR=02D0 MS=FFF5 PS=0016 V0 D0 I0 T0 S0 Z0 A1 P1 C0 
0200:016D FF6E06          JMP      FAR [BP+06]

The far address at [BP+6] is 02F0:0000.