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Fixed a couple of PDP-10 opcode emulation bugs (AOBJN, AOBJP, and CMP), and rounded out the set of DEC's basic instruction diagnostics

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Jeff 2017-03-27 11:44:42 -07:00 • committed by Jeff Parsons
commit 2a8c2a74d2
21 changed files with 29570 additions and 84 deletions
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94
_posts/2017-03-24-stepping-through-pdp-10-diagnostica.md → _posts/2017-03-24-stepping-through-pdp-10-diagnostics.md
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@ -8,10 +8,10 @@ machines:
type: pdp10
config: /devices/pdp10/machine/ka10/test/debugger/machine.xml
debugger: true
commands: a 30724 /apps/pdp10/diags/klad/dakaa/MYDAKAA.MAC
commands: a 30724 /apps/pdp10/diags/klad/dakaa/DAKAA.MAC
---
Now that the PDPjs MACRO-10 Mini-Assembler is [limping along](/blog/2017/03/21/), it was time to start assembling some
Now that the PDPjs MACRO-10 Mini-Assembler is [limping along](/blog/2017/03/21/), it's time to start assembling some
of DEC's PDP-10 diagnostics and loading them into a test machine. The first diagnostic I tried was
[KA10 Basic Instruction Diagnostic #1 (MAINDEC-10-DAKAA-B-D)](/apps/pdp10/diags/klad/dakaa/), which has been loaded into
the machine below.
@ -20,9 +20,9 @@ the machine below.
Here were the results of my first run attempt:
>> a 30724 /apps/pdp10/diags/klad/dakaa/MYDAKAA.MAC
>> a 30724 /apps/pdp10/diags/klad/dakaa/DAKAA.MAC
starting PCjs MACRO-10 Mini-Assembler...
loading MYDAKAA.MAC
loading DAKAA.MAC
CPU will not be auto-started (click Run to start)
2844 words loaded at 030724-036357
00=000000000000 01=000000000000 02=000000000000 03=000000000000
@ -60,9 +60,9 @@ Happily, this was a good outcome, because 035057 is the end of the test. If you
Next, I tried [KA10 Basic Instruction Diagnostic #4 (MAINDEC-10-DAKAD-B-D)](/apps/pdp10/diags/klad/dakad/):
>> a 30724 /apps/pdp10/diags/klad/dakad/MYDAKAD.MAC
>> a 30724 /apps/pdp10/diags/klad/dakad/DAKAD.MAC
starting PCjs MACRO-10 Mini-Assembler...
loading MYDAKAD.MAC
loading DAKAD.MAC
1986 words loaded at 030724-034625
00=000000000000 01=000000000000 02=777777777777 03=000000000000
04=777777777777 05=000000000000 06=000000000000 07=777777777777
@ -91,8 +91,88 @@ Next, I tried [KA10 Basic Instruction Diagnostic #4 (MAINDEC-10-DAKAD-B-D)](/app
032005: 312140 034462 CAME 3,34462 ;history=2
032006: 254200 032007 HALT 32007 ;history=1
This looked less good.
This looked less good. Both AC3 and memory location 34462 contained 400000000000, so the CAME instruction should have
"skipped if equal." There was a bug in the [cpuops.js](/modules/pdp10/lib/cpuops.js) *CMP()* function:
```javascript
/**
* CMP(dst, src)
*
* Performs the SIGNED comparison (CMP) of two 36-bit operands.
*
* @param {number} dst (36-bit value)
* @param {number} src (36-bit value)
* @return {number} (dst - src)
*/
PDP10.CMP = function(dst, src)
{
return (dst < PDP10.INT_LIMIT? dst : dst - PDP10.WORD_LIMIT) - (src < PDP10.INT_LIMIT? src : src - PDP10.INT_LIMIT);
};
```
And here's the correction:
```javascript
return (dst < PDP10.INT_LIMIT? dst : dst - PDP10.WORD_LIMIT) - (src < PDP10.INT_LIMIT? src : src - PDP10.WORD_LIMIT);
```
Just a stupid typo. After fixing that and trying again, the diagnostic got a bit farther:
>> g
running
stopped (1119 instructions, 1118 cycles, 12 ms, 93167 hz)
00=000001000001 01=000000000000 02=000000000002 03=000000000003
04=000000000004 05=000000000005 06=000000000006 07=000000000007
10=000000000010 11=000000000011 12=000000000012 13=000000000013
14=000000000014 15=000000000015 16=000000000016 17=000000777723
PC=033446 RA=00033446 EA=033446 C0=0 C1=0 OV=0 ND=0 PD=0
033446: 324000 033447 JUMPA 0,33447
>> dh
033432: 253000 033434 AOBJN 0,33434 ;history=10
033434: 324000 033435 JUMPA 0,33435 ;history=9
033435: 200000 034573 MOVE 0,34573 ;history=8
033436: 252000 033440 AOBJP 0,33440 ;history=7
033437: 334000 000000 SKIPA 0,0 ;history=6
033441: 324000 033442 JUMPA 0,33442 ;history=5
033442: 474000 000000 SETO 0,0 ;history=4
033443: 253000 033444 AOBJN 0,33444 ;history=3
033444: 312000 034574 CAME 0,34574 ;history=2
033445: 254200 033446 HALT 33446 ;history=1
The problem here was that after `SETO 0,0`, AC0 contained 777777777777, so when AOBJN added 000001000001 to it, the result
should have been 000001000000, but because other another typo, this time in the *opAOBJN()* function:
```javascript
/**
* opAOBJN(0o253000): Add One to Both Halves of AC and Jump if Negative
*
* From the DEC PDP-10 System Reference Manual (May 1968), p. 2-41:
*
* Add 1000001 [base 8] to AC and place the result back in AC. If the result is less than zero
* (ie if bit 0 is 1, and hence a negative count in the left half has not yet reached zero or a positive
* count has reached 2^17), take the next instruction from location E and continue sequential operation
* from there.
*
* The incrementing of both halves of AC simultaneously is effected by adding 1000001 [base 8]. A count
* of -2 in AC left is therefore increased to zero if 2^18 - 1 is incremented in AC right.
*
* @this {CPUStatePDP10}
* @param {number} op
* @param {number} acc
*/
PDP10.opAOBJN = function(op, acc)
{
var dst = (this.readWord(acc) + 0o000001000001) % PDP10.WORD_MASK;
this.writeWord(acc, dst);
if (dst >= PDP10.INT_LIMIT) this.setPC(this.regEA);
};
```
when `dst` became 0o1000001000000 and exceeded WORD_MASK (0o777777777777), it needed to be mod'ed with WORD_LIMIT (0o1000000000000),
not WORD_MASK, to truncate the value to 36 bits. Here's the corrected line:
```javascript
var dst = (this.readWord(acc) + 0o000001000001) % PDP10.WORD_LIMIT;
```
*[@jeffpar](http://twitter.com/jeffpar)*
*Mar 24, 2017*