XOR A with A
= A to CR0
Then it loads a quad (32 bits) to VGA using a flat quad address for the
screen, 0xb8800. And there they are; two characters and two attributes in
one load, burbling happily. Runs in flat 32-bit with protection off, in
other words. I also forgot to use a short loop, so you'll see that it's a
quad relative jump.
IRQs are off. It looks like for a 32-bit unprotected OS you need
8086-style intvecs in the IDT. That's the only real annoyance I see at
this point. This occured to me because I had been assuming rmode vectors
off 0 like an 8086. So Squeal Mode is still on the slab, but Forreal Mode
is up and geekin.
Forreal Mode. Part of this complete Squeal Mode.
INT is rated faster for real mode than pmode, but that might just be
because they are talking about a 16 bit return addy. If not, Forreal Mode
should be interesting for realtime stuff and truly sophistry-free
operating systems like AmigaDos. INT I think is rated 37 clocks rmode, 59
pmode or thereabouts.
What happens when you load DS with 0xb800 or something is LAAETTR. And of
course, I wouldn't be seen in the same convention hall with a paged
Forreal Mode. Or a true 32-bit Minix.
In other words, what INTeL says you're supposed to do when going to real
mode is to be suffixed with "if you're trying to run Dos." Which was quite
legitimate concern in 1986. Conversely, aspects of a segent descriptor
persist if you flip PE after setting up the segment. Like USE32 is USE32
in real or pmode. Once USE32 is set for your code segment, rmode can't
unset it. Hence the recommended INTeL ceremonies.
Rick Hohensee
Precision Mojo Engineer
00000000 00... ALLOT 0x7C00
00007c00 270 28 02 = 552 to A
00007c03 271 01 00 = 1 to C
00007c06 31 322 XOR D with D
00007c08 8e 302 = D to ES
00007c0a 273 00 7c = 0x7c00 to B
00007c0d cd 13 submit 0x13
00007c0f fa nosurprises
00007c10 270 00 b8 = 0xb800 to A
00007c13 8e 330 = A to DS
00007c15 270 48 68 = 0x6848 to A
00007c18 89 006 20 02 = A to @ 544
00007c1c 31 300 XOR A with A
00007c1e 8e 330 = A to DS
00007c20 0f 01 16 7e 7d setGDT initial_gdtr
00007c25 270 00 b8 = 0xb800 to A
00007c28 8e 330 = A to DS
00007c2a 270 61 61 = 0x6161 to A
00007c2d 89 006 c0 02 = A to @ 704
00007c31 270 01 00 = 1 to A 0f 01 f0
00007c37 e9 00 00 jump PMODE16
00007c3a (O) PMODE16
00007c3a 270 33 f2 = 0xf233 to A
00007c3d 89 006 60 03 = A to @ 864
00007c41 ea 46 7c 10 00 far jump addr./GDTindex ptr
00007c46 (O) BIG_CS
00007c46 270 4e 33 73 27 = 0x2773334e to A
00007c4b 89 005 00 04 00 00 = A to @ 1024
00007c51 270 18 00 00 00 = 0x18 to A
00007c56 8e 330 = A to DS
00007c58 8e 300 = A to ES
00007c5a (O) BIG_DS
00007c5a 270 21 3a 6d 27 = 0x276d3a21 to A
00007c5f 89 005 a0 84 0b 00 = A to @ 754848
00007c65 31 300 XOR A with A
00007c67 8e 340 = A to FS
00007c69 8e 350 = A to GS
00007c6b (O) nullifiedextrasegments
00007c6b 270 75 84 74 00 = 0x748475 to A
00007c70 89 005 60 88 0b 00 = A to @ 755808
00007c76 270 18 00 00 00 = 0x18 to A
00007c7b 8e 320 = A to SS
00007c7d 270 d1 00 00 00 = 0xd1 to A
00007c82 272 64 00 00 00 = 0x64 to D
00007c87 ee send byte
00007c88 90 nop
00007c89 90 nop
00007c8a 90 nop
00007c8b 90 nop
00007c8c 90 nop
00007c8d 90 nop
00007c8e 90 nop
00007c8f 90 nop
00007c90 90 nop
00007c91 90 nop
00007c92 270 df 00 00 00 = 0xdf to A
00007c97 272 60 00 00 00 = 0x60 to D
00007c9c ee send byte
00007c9d 272 92 00 00 00 = 0x92 to D
00007ca2 ec recieve byte
00007ca3 0d 02 00 00 00 OR 2 to A
00007ca8 ee send byte
00007ca9 (O) a20loop
00007ca9 270 55 55 aa aa = 0xaaaa5555 to A
00007cae 89 005 d8 ff 1f 00 = A to @ 2097112
00007cb4 8b 035 d8 ff 1f 00 = @ 2097112 to B
00007cba 39 303 -test A to B
00007cbc 0f 85 e7 ff ff ff when not zero a20loop
00007cc2 274 f0 ef 00 00 = 61424 to SP
00007cc7 (O) defaultallvectors
00007cc7 31 377 XOR DI with DI
00007cc9 (O) perIDTvector
00007cc9 60 pushcore
00007cca 270 0c 7e 00 00 = twitch to A
00007ccf e8 00 01 00 00 call install
00007cd4 61 pullcore
00007cd5 107 1+ DI
00007cd6 81 377 7f 00 00 00 -test 127 with DI
00007cdc 0f 85 e7 ff ff ff when not zero perIDTvector
00007ce2 (O) defaultallIRQs
00007ce2 277 20 00 00 00 = 0x20 to DI
00007ce7 (O) perIRQvector
00007ce7 60 pushcore
00007ce8 270 1c 7e 00 00 = IRQtwitch to A
00007ced e8 e2 00 00 00 call install
00007cf2 61 pullcore
00007cf3 107 1+ DI
00007cf4 81 377 30 00 00 00 -test 0x30 with DI
00007cfa 0f 85 e7 ff ff ff when not zero perIRQvector
00007d00 277 20 00 00 00 = 0x20 to DI
00007d05 60 pushcore
00007d06 270 3f 7e 00 00 = IRQ0twitch to A
00007d0b e8 c4 00 00 00 call install
00007d10 61 pullcore
00007d11 0f 01 1d 67 7e 00 00 setIDT 32359
00007d18 (O) PICprogram
00007d18 270 11 00 00 00 = 17 to A
00007d1d 272 20 00 00 00 = 0x20 to D
00007d22 ee send byte
00007d23 272 a0 00 00 00 = 0xa0 to D
00007d28 ee send byte
00007d29 270 20 00 00 00 = 0x20 to A
00007d2e 272 21 00 00 00 = 0x21 to D
00007d33 ee send byte
00007d34 270 28 00 00 00 = 40 to A
00007d39 272 a1 00 00 00 = 0xa1 to D
00007d3e ee send byte
00007d3f 270 04 00 00 00 = 4 to A
00007d44 272 21 00 00 00 = 0x21 to D
00007d49 ee send byte
00007d4a 270 02 00 00 00 = 2 to A
00007d4f 272 a1 00 00 00 = 0xa1 to D
00007d54 ee send byte
00007d55 270 01 00 00 00 = 1 to A
00007d5a 272 21 00 00 00 = 0x21 to D
00007d5f ee send byte
00007d60 272 a1 00 00 00 = 0xa1 to D
00007d65 ee send byte
00007d66 31 300 XOR A with A
00007d68 0f 20 300 = A to CR0
00007d6b 270 44 34 19 18 = 0x18193444 to A
00007d70 (O) fmodeloop
00007d70 89 005 00 88 0b 00 = A to @ 755712
00007d76 100 1+ A
00007d77 e9 f4 ff ff ff jump fmodeloop
00007d7c f4 halt
00007d7d f4 halt
00007d7e (O) initial_gdtr
00007d7e 00 04 84 7d 00 00
00007d84 (O) GDT
00007d84 00 00 00 00 00 00 00 00 0 the required NULL
00007d8c ff ff 00 00 00 89 cf 00 1 0x8 TSS
stackstack
00007d94 ff ff 00 00 00 9a cf 00 2 0x10 ring0 USE32
CS
00007d9c ff ff 00 00 00 92 cf 00 3 0x18 ring0 data
00007da4 ff ff 00 00 00 9a 00 00 4 0x20 USE16 CS
00007dac ff ff 00 00 00 92 00 00 5 0x28 USE16 data
?S
00007db4 00 00 00 00 00 00 00 00 6 0x30
00007dbc 00 00 00 00 00 00 00 00 7 0x38
00007dc4 00 00 00 00 00 00 00 00 8 0x40
00007dcc 00 00 00 00 00 00 00 00 9 0x48
00007dd4
00007dd4 (O) install
00007dd4 273 10 00 00 00 = 16 to B
00007dd9 271 0e 00 00 00 = 14 to C
00007dde c1 347 03 upshift 3 to DI
00007de1 81 307 00 10 00 00 + 0x1000 to DI
00007de7 (O) makegate
00007de7 89 302 = A to D
00007de9 81 342 ff ff 00 00 AND 0x0000ffff to D
00007def 81 312 00 00 10 00 OR 0x100000 to D
00007df5 89 027 = D to @ DI
00007df7 c1 341 08 upshift 8 to C
00007dfa 81 311 00 80 00 00 OR 0x8000 to C
00007e00 81 340 00 00 ff ff AND 0xffff0000 to A
00007e06 09 301 OR A to C
00007e08 89 117 04 = C to @ 4 DI
00007e0b c3 return
00007e0c (O) twitch
00007e0c 120 push A
00007e0d 8b 005 32 8a 0b 00 = @ 756274 to A
00007e13 100 1+ A
00007e14 89 005 32 8a 0b 00 = A to @ 756274
00007e1a 130 pull A
00007e1b cf dismiss
00007e1c (O) IRQtwitch
00007e1c 120 push A
00007e1d 8b 005 0e 81 0b 00 = @ 753934 to A
00007e23 100 1+ A
00007e24 89 005 0e 81 0b 00 = A to @ 753934
00007e2a 122 push D
00007e2b 270 20 00 00 00 = 32 to A
00007e30 272 a0 00 00 00 = 0xa0 to D
00007e35 ee send byte
00007e36 272 20 00 00 00 = 0x20 to D
00007e3b ee send byte
00007e3c 132 pull D
00007e3d 130 pull A
00007e3e cf dismiss
00007e3f (O) IRQ0twitch
00007e3f 120 push A
00007e40 8b 005 6e 80 0b 00 = @ 753774 to A
00007e46 81 300 07 b2 01 00 + 111111 to A
00007e4c 89 005 6e 80 0b 00 = A to @ 753774
00007e52 122 push D
00007e53 270 20 00 00 00 = 32 to A
00007e58 272 a0 00 00 00 = 0xa0 to D
00007e5d ee send byte
00007e5e 272 20 00 00 00 = 0x20 to D
00007e63 ee send byte
00007e64 132 pull D
00007e65 130 pull A
00007e66 cf dismiss
00007e67 (O) initial_IDTreg
00007e67 00 02 00 10 00 00
00007e6d (O) Cat
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