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| author | H. Peter Anvin <hpa@zytor.com> | 2014-05-11 16:35:11 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2014-05-11 16:35:11 -0700 |
| commit | fbd3070fba255b7ec16fd8eb91abd3156916bb63 (patch) | |
| tree | a0b41a98552372208b42b43177694042f49ea35e | |
| parent | 837edd686efd1bb3454bd6597509f93ba0a05f30 (diff) | |
| download | abc80-fbd3070fba255b7ec16fd8eb91abd3156916bb63.tar.gz abc80-fbd3070fba255b7ec16fd8eb91abd3156916bb63.tar.xz abc80-fbd3070fba255b7ec16fd8eb91abd3156916bb63.zip | |
CP/M: Always clear memory beyond the BIOS
Always clear the memory beyond the BIOS. It also means we don't have
to store it explicitly as a bunch of zeroes in cpm.bas.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
| -rw-r--r-- | data/Makefile | 4 | ||||
| -rw-r--r-- | data/cbios.asm | 5 | ||||
| -rw-r--r-- | data/cpm.asm | 9 |
3 files changed, 12 insertions, 6 deletions
diff --git a/data/Makefile b/data/Makefile index 673889c..9048cc6 100644 --- a/data/Makefile +++ b/data/Makefile @@ -56,7 +56,9 @@ chargen.mif : chargen.bin $(BIN2MIF) videoram.bin: video.txt genvideo.pl $(PERL) genvideo.pl -40 < $< > $@ || ( rm -f $@ ; exit 1 ) -cpm.bin: cpm.asm cbios.bin +cpm.bin: cpm.asm cbios.bin stripzero.pl + $(Z80ASM) -o$@ -l$*.lst $< + $(PERL) stripzero.pl $@ cpm.bas: cpm.bin $(PERL) bin2poke.pl $< 32768 100 'Z%=CALL(32768%)' > $@ \ diff --git a/data/cbios.asm b/data/cbios.asm index 3d30a63..caaa382 100644 --- a/data/cbios.asm +++ b/data/cbios.asm @@ -553,8 +553,6 @@ bootmsg: db "CP/M BIOS (H. Peter Anvin, 2014-05-09)\r\n" ;--------------------------------------------------------------------------------------------------------------- - - ; scratch RAM used by BIOS curdisk: db 0 cursector: db 0 @@ -572,6 +570,3 @@ chk00: ds 0 ; check vector for disk 0 (must be CKS bytes long) chk01: ds 0 ; check vector for disk 1 (must be CKS bytes long) chk02: ds 0 ; check vector for disk 2 (must be CKS bytes long) chk03: ds 0 ; check vector for disk 3 (must be CKS bytes long) - -db "</bios>" -; we point the stack at 0x0000 on restart, so that may overwrite the very end of RAM. diff --git a/data/cpm.asm b/data/cpm.asm index 1299aec..061a3c3 100644 --- a/data/cpm.asm +++ b/data/cpm.asm @@ -36,6 +36,15 @@ _start: ld bc,bios_size ldir + ; Zero memory above the BIOS + ld l,e + ld h,d + inc de + ld bc,CPMCURSOR-(CPMBIOS+bios_size)-1 + xor a + ld (hl),a + ldir + jp CPMBIOS bios: |