Ahmes is a computer used in some computer architecture classes. There is an executable file in the repository. It can be ran natively on Windows or using Wine under Linux.
You will need Git LFS in order to get the executable from the command line.
Everything here is licensed under the BSD 2-Clause license, except for the simulator itself.
The maintainer of this repository is working on a fully-compatible simulator for Ahmes using Python. This is a step in the direction of making software usable by everyone.
The computer has 256 bytes of memory.
There are also two registers: the accumulator (AC) and the program counter (PC).
The computer also has five indicators:
N - negative, set if the last operation produced a negative result
Z - zero, set if the last operation produced zero
V - overflow, set if the last operation resulted in an overflow
C - carry, set if the last operation resulted in a carry-out
B - borrow, set if the last operation resulted in a borrow
MSB - most significant bit
LSB - least significant bit
NOP - no operation
STA ADDRESS - stores AC on ADDRESS
LDA ADDRESS - loads ADDRESS on AC
AND ADDRESS - bitwise AND with the byte at ADDRESS
OR ADDRESS - bitwise OR with the byte at ADDRESS
NOT - bitwise NOT
ADD ADDRESS - two's complement addition with the byte at ADDRESS
SUB ADDRESS - two's complement subtraction with the byte at ADDRESS
SHR - shifts the AC one bit to the right
SHL - shifts the AC one bit to the left
ROR - rotates the AC one bit to the right (the LSB becomes the MSB)
ROL - rotates the AC one bit to the left (the MSB becomes the LSB)
A jump is a modification of the program counter. Jumping to X and setting the PC to X are practically the same thing here.
JMP ADDRESS - jumps to ADDRESS
JN ADDRESS - if N, jumps to ADDRESS
JP ADDRESS - if not N, jumps to ADDRESS
JV ADDRESS - if V, jumps to ADDRESS
JNV ADDRESS - if not V, jumps to ADDRESS
JZ ADDRESS - if Z, jumps to ADDRESS
JNZ ADDRESS - if not Z, jumps to ADDRESS
JC ADDRESS - if C, jumps to ADDRESS
JNC ADDRESS - if not C, jumps to ADDRESS
JB ADDRESS - if B, jumps to ADDRESS
JNB ADDRESS - if not B, jumps to ADDRESS
HLT - halts the program execution
When the program counter points to a byte with a code, the instruction to be executed is selected according to the following table.
Each instruction is indicated by a byte value in the range [Code, Maximum Code].
| Code | Maximum Code | Mnemonic |
|---|---|---|
| 0 | 15 | NOP |
| 16 | 31 | STA |
| 32 | 47 | LDA |
| 48 | 63 | ADD |
| 64 | 79 | OR |
| 80 | 95 | AND |
| 96 | 111 | NOT |
| 112 | 127 | SUB |
| 128 | 143 | JMP |
| 144 | 147 | JN |
| 148 | 151 | JP |
| 152 | 155 | JV |
| 156 | 159 | JNV |
| 160 | 163 | JZ |
| 164 | 175 | JNZ |
| 176 | 179 | JC |
| 180 | 183 | JNC |
| 184 | 187 | JB |
| 188 | 223 | JNB |
| 224 | 224 | SHR |
| 225 | 225 | SHL |
| 226 | 226 | ROR |
| 227 | 239 | ROL |
| 240 | 255 | HLT |
Only the first code value is mapped to the instruction, all other instruction codes that would map to the instruction will then map to NOP.
ones.mem - A memory file whose bytes are all set to the value 1.