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VAX, VAX780: Added hook for unpredictable indexed immediate

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Originally, the VAX allowed immediate operands (8F) to be used without
restrictions in address mode instructions, either standalone or indexed.
Starting with MicroVAX II, immediate indexed became reserved. This
remained true for all subsequent chip implementations. The SRM was
ECOed in March, 1985 to make immediate indexed unpredictable.

In MicroVAX II, immediate g-floating operands didn't work correctly. The
problem was found a couple of months after tape-out. While the index
flows could be fixed, and were fixed according to the microcode revision
history:

;    7-May-84    [RMS]    Fixed FD problem in index flows (JLR)

the problem in indexed immediate could only be fixed by a significant
hardware change in an area that was already packed full. The VAX
Architecture Team, which had always been very sympathetic to the
VAX chip efforts, proposed a much simpler solution: make immediate
indexed unpredictable. It was useless, in any case.

I'm rather surprised that this wasn't flagged by the 780 diagnostics.
Maybe it was never tested. It was tested in HCORE (the original MicroVAX I
core diagnostic that is failing), but I removed it subsequently:

; 8-may-85    rms    removed indexed immediate tests

Bottom line - the simulator is right for the chip VAXes (including, I think,
V11) and wrong for MicroVAX I and probably the 8600, 780, 750, and 730.
This commit is contained in:
Bob Supnik
2019-04-23 11:56:55 -07:00
committed by Mark Pizzolato
parent e4f8313262
commit cf9ead8d04
5 changed files with 18 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
VAX/vax780_bug_history.txt
View File

@@ -61,7 +61,7 @@ Bugs Found And Fixed During Simulator Debug
58. POLYx: add step <does> require truncation (proved by AXE tests).
59. Unaligned references to IO space: incorrect on CVAX.
60. REI to compatibility mode: PSL<dv,fu,iv> were not checked for mbz.
61. Indexed immediate not does fault.

4
VAX/vax780_defs.h
View File

@@ -1,6 +1,6 @@
/* vax780_defs.h: VAX 780 model-specific definitions file
Copyright (c) 2004-2017, Robert M Supnik
Copyright (c) 2004-2019, Robert M Supnik
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
@@ -23,6 +23,7 @@
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from Robert M Supnik.
23-Apr-19 RMS Added hook for unpredictable indexed immediate .aw
18-May-17 RMS Added model-specific AST validation test
19-Jan-17 RMS Moved CR to BR6 (Mark Pizzolato)
29-Mar-15 RMS Added model specific IPR max
@@ -151,6 +152,7 @@
#define MT_AST_TEST(r) r = (r) & 07; \
if ((r) > AST_MAX) RSVD_OPND_FAULT
#define IDX_IMM_TEST
/* Memory */

23
VAX/vax_cpu.c
View File

@@ -25,6 +25,7 @@
cpu VAX central processor
23-Apr-19 RMS Added hook for unpredictable indexed immediate .aw
14-Apr-19 RMS Added hook for non-standard MxPR CC's
31-Mar-17 RMS Fixed uninitialized variable on FPD path (COVERITY)
13-Mar-17 RMS Fixed dangling else in show_opnd (COVERITY)
@@ -886,20 +887,11 @@ for ( ;; ) {
case AIN|VB:
case AIN|WB: case AIN|WW: case AIN|WL: case AIN|WQ: case AIN|WO:
/* CHECK_FOR_PC; */
opnd[j++] = OP_MEM;
case AIN|AB: case AIN|AW: case AIN|AL: case AIN|AQ: case AIN|AO:
va = opnd[j++] = R[rn];
if (rn == nPC) {
if (DR_LNT (disp) >= L_QUAD) {
GET_ISTR (temp, L_LONG);
GET_ISTR (temp, L_LONG);
if (DR_LNT (disp) == L_OCTA) {
GET_ISTR (temp, L_LONG);
GET_ISTR (temp, L_LONG);
}
}
else GET_ISTR (temp, DR_LNT (disp));
SETPC (PC + DR_LNT (disp));
}
else {
R[rn] = R[rn] + DR_LNT (disp);
@@ -1410,10 +1402,15 @@ for ( ;; ) {
break;
case AIN:
CHECK_FOR_PC;
index = index + R[rn];
R[rn] = R[rn] + DR_LNT (disp);
recq[recqptr++] = RQ_REC (AIN | (disp & DR_LNMASK), rn);
if (rn == nPC) {
IDX_IMM_TEST;
SETPC (PC + DR_LNT (disp));
}
else {
R[rn] = R[rn] + DR_LNT (disp);
recq[recqptr++] = RQ_REC (AIN | (disp & DR_LNMASK), rn);
}
break;
case AID:

2
VAX/vax_defs.h
View File

@@ -602,7 +602,7 @@ enum opcodes {
#define STR_GETDPC(x) (((x) >> STR_V_DPC) & STR_M_DPC)
#define STR_GETCHR(x) (((x) >> STR_V_CHR) & STR_M_CHR)
#define STR_PACK(m,x) ((((PC - fault_PC) & STR_M_DPC) << STR_V_DPC) | \
(((m) & STR_M_CHR) << STR_V_CHR) | ((x) & STR_LNMASK))
(((m) & STR_M_CHR) << STR_V_CHR) | ((x) & STR_LNMASK))
/* Read and write */

4
VAX/vaxmod_defs.h
View File

@@ -1,6 +1,6 @@
/* vaxmod_defs.h: VAX model-specific definitions file
Copyright (c) 1998-2017, Robert M Supnik
Copyright (c) 1998-2019, Robert M Supnik
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
@@ -23,6 +23,7 @@
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from Robert M Supnik.
23-Apr-19 RMS Added hook for unpredictable indexed immediate .aw
18-May-17 RMS Added model-specific AST validation test
29-Mar-15 RMS Added model-specific IPR max
20-Dec-13 RMS Added prototypes for unaligned IO and register handling
@@ -217,6 +218,7 @@
#define LP_AST_TEST(r)
#define LP_MBZ84_TEST(r)
#define LP_MBZ92_TEST(r)
#define IDX_IMM_TEST RSVD_ADDR_FAULT /* fault on indexed imm */
#define MT_AST_TEST(r) if ((r) > AST_MAX) RSVD_OPND_FAULT