Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss

When I finally prove my point everyone shuts up [x86 is Turing complete]

3 views
Skip to first unread message

olcott

unread,
Aug 18, 2020, 9:50:05 PM8/18/20
to
The abstract model of computation specified by the x86 language already
has access to unlimited memory when we assume the implementation detail
that the underlying memory architecture of this abstract model is
organized as an unlimited sequence of adjacent 4GB blocks.

(1) signed 32-bit relative jumps
// Jumps to the first address of the next 4GB block
FFFFFFF0: E90B000000 ; signed 32-bit relative jumps

(2) signed 32-bit relative offsets
// Moves a 32-bit integer from the first address of the next 4GB block
xxxxxxxx: BBFFFFFFFF mov ebx, 0xffffffff
xxxxxxxx: 8B4301 mov eax, dword ptr [ebx+0x1]

x86 Instruction Set Reference
https://c9x.me/x86/

The correctness of the above machine language instructions was verified
with Intel XED.

The X86 Encoder Decoder (XED), is a software library (and associated
headers) for encoding and decoding X86 (IA32 and Intel64) instructions.
https://intelxed.github.io/

E9 cd JMP rel32
Jump near, relative, displacement relative to next instruction.

f0: E90B000000 jmp 0x100
f5: 90 nop
f6: 90 nop
f7: 90 nop
f8: 90 nop
f9: 90 nop
fa: 90 nop
fb: 90 nop
fc: 90 nop
fd: 90 nop
fe: 90 nop
ff: 90 nop
100: BBFFFFFFFF mov ebx, 0xffffffff
105: 8B4301 mov eax, dword ptr [ebx+0x1]

--
Copyright 2020 Pete Olcott
0 new messages