PCjs Machines
Home of the original IBM PC emulator for browsers.
DEC PDP-10 Opcode Tests
The PDP-10 machine below loads the following PDPjs opcode test:
Details on how to run and modify the test, and perform similar tests in SIMH, are provided below.
[PCjs Machine "testka10"]
Waiting for machine "testka10" to load....
The PDP-10 Half-Word Opcode Test file specifies that the following words:
0o505040111111, // HRLI 1,111111
0o541040444444, // HRRI 1,444444
0o544100000001, // HLR 2,1
0o504100000001, // HRL 2,1
...
should be loaded at address 0o100, and that the program counter (PC register) should be set to 0o100. The embedded comments display the instructions that correspond to each word.
If you want to alter or add new instructions, the PDP-10 Debugger now includes a rudimentary assembler. Using the a command,
along with an optional start address, you can enter “assembler mode”. For example, here’s how the first four instructions from
the PDP-10 Half-Word Opcode Test could be entered by hand:
>> a 100
begin assemble at 000100
>> hrli 1,111111
000100: 505040 111111 HRLI 1,111111
>> hrri 1,444444
000101: 541040 444444 HRRI 1,444444
>> hlr 2,1
000102: 544100 000001 HLR 2,1
>> hrl 2,1
000103: 504100 000001 HRL 2,1
ended assemble at 000104
Entering a blank line exits “assembler mode”. To disassemble the four instructions, use u 100 l4:
>> u 100 l4
000100: 505040 111111 HRLI 1,111111
000101: 541040 444444 HRRI 1,444444
000102: 544100 000001 HLR 2,1
000103: 504100 000001 HRL 2,1
You can also copy-and-paste a series of instructions into the PDPjs Debugger, as long as each command ends with a semicolon:
a 100;
hrli 1,111111;
hrri 1,444444;
hlr 2,1;
hrl 2,1;
end
Individual instructions can also be assembled without entering “assembler mode”, as long as you precede
each instruction with the a command and a specific address:
a 100 hrli 1,111111;
a 101 hrri 1,444444;
a 102 hlr 2,1;
a 103 hrl 2,1
Individual instructions can be executed with the t command and memory can be dumped with the d command.
After executing the first four instructions and using the d 0 l4 command to dump first four words of memory
(also known as AC registers 0-3), you should see the following output:
>> r
000100: 505040 111111 HRLI 1,111111
>> t
000101: 541040 444444 HRRI 1,444444
>> t
000102: 544100 000001 HLR 2,1
>> t
000103: 504100 000001 HRL 2,1
>> t
000104: 000000 000000 UUO 0,0
>> d 0 l4
000000: 000000 000000 111111 444444 444444 111111 000000 000000
To assemble and test the same instructions in SIMH, using the pdp10 binary:
sim> dep 100 505040111111
sim> dep 101 541040444444
sim> dep 102 544100000001
sim> dep 103 504100000001
sim> ex -m 100-103
100: HRLI 1,111111
101: HRRI 1,444444
102: HLR 2,1
103: HRL 2,1
sim> dep pc 100
sim> step
Step expired, PC: 000101 (HRRI 1,444444)
sim> step
Step expired, PC: 000102 (HLR 2,1)
sim> step
Step expired, PC: 000103 (HRL 2,1)
sim> step
Step expired, PC: 000104 (000000000000)
sim> ex 0-3
0: 000000000000
1: 111111444444
2: 444444111111
3: 000000000000