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kernel
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correct xor to test not clear value, invert test so 808x is 0 and NEC is 1 matching returned value

This commit is contained in:
Kenneth J Davis 2024-02-04 19:38:42 -05:00
parent 07155e6184
commit f7bf549544
2 changed files with 7 additions and 5 deletions
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10
kernel/cpu.asm
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@ -53,15 +53,15 @@ CPU 386
; based on https://hg.pushbx.org/ecm/ldebug/file/7f3440d5824d/source/init.asm#l3071 ; based on https://hg.pushbx.org/ecm/ldebug/file/7f3440d5824d/source/init.asm#l3071
; which is based on http://www.textfiles.com/hamradio/v20_bug.txt ; which is based on http://www.textfiles.com/hamradio/v20_bug.txt
mov ax, sp ; we use stack to do test mov ax, sp ; we use stack to do test
mov cx, 1 ; after pop still 1 if 8088/8086 mov cx, 0 ; after pop still 0 if 8088/8086
push cx push cx
dec cx ; after pop still 0 if NEC V20/V30 inc cx ; after pop still 1 if NEC V20/V30
; next instructions may lock system if breakpoint or trace flag set ; next instructions may lock system if breakpoint or trace flag set
db 8Fh, 0C1h; pop r/m16 with operand cx on 808x, nop on NEC V20/V30 db 8Fh, 0C1h; pop r/m16 with operand cx on 808x, nop on NEC V20/V30
mov sp, ax ; reset stack to known good state (pre push, optional pop) mov sp, ax ; reset stack to known good state (pre push, optional pop)
xor cx, cx ; cx is 1 if NEC, 0 if 808x or cx, cx ; cx is 0 if 808x, 1 if NEC
jz is808x jz is808x ; if not NEC then goto test for 808x vs 8018x
mov bx, cx mov bx, cx ; treat NEC V20/V30 as 8018x, i.e. return 1
jmp short cleanup jmp short cleanup
is808x: is808x:
mov ax,1 ; determine if 8086 or 186 mov ax,1 ; determine if 8086 or 186

2
kernel/main.c
View File

@ -461,6 +461,8 @@ STATIC VOID signon()
" - 80386 CPU required" " - 80386 CPU required"
#elif defined (I186) #elif defined (I186)
" - 80186 CPU required" " - 80186 CPU required"
#else
" - 808x compatible"
#endif #endif
#ifdef WITHFAT32 #ifdef WITHFAT32