From 6076a48f2514f47048fee3cd4fd8c39bdf8e179c Mon Sep 17 00:00:00 2001
From: Timothe Litt <tlhackque@yahoo.com>
Date: Tue, 18 Jun 2013 21:14:32 -0400
Subject: [PATCH] PDP-10 RP redux

The KS front end microcode actually reads the wrong alternate HOM block.
Teach the bootstrap to try the wrong one (in case someone counts on
this), but also the correct block.

Implement boot -A to emulate an autoboot - the boot that happens on
power-on or when the boot switch is pressed.  No questions, just boots.
---
 PDP10/pdp10_rp.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/PDP10/pdp10_rp.c b/PDP10/pdp10_rp.c
index bbf65728..83d32814 100644
--- a/PDP10/pdp10_rp.c
+++ b/PDP10/pdp10_rp.c
@@ -1215,6 +1215,9 @@ return SCPE_OK;
  * The DEC and ITS versions are word-for-word identical, except that
  * the DEC RDIO/WRIO are replaced by IORDQ and IOWRQ.  This is hand
  * assembled code, so please always make changes in both.
+ * Due to a typo in the KS Console rom, block 010 is read for the
+ * alternate HOM block.  The correct block is 012.  For compatibiliy,
+ * we will do what the hardware did first, what's right if it fails (as it will).
  */
 
 #define BOOT_START      0377000                         /* start */
@@ -1241,13 +1244,13 @@ static const d10 boot_rom_dec[] = {
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
     INT64_C(0306140505755),                 /*      cain 3,sixbit /HOM/ */
-    INT64_C(0254000377032),                 /*      jrst .+6        ; match */
+    INT64_C(0254000377032),                 /*      jrst pg         ; match */
     INT64_C(0201100000010),                 /*      movei 2,10      ; blk #10 */
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
     INT64_C(0302140505755),                 /*      caie 3,sixbit /HOM/ */
-    INT64_C(0254200377031),                 /*      halt .          ; inv home */
-    INT64_C(0336100001103),                 /*      skipn 2,1103    ; pg of ptrs */
+    INT64_C(0254000377061),                 /*      jrst alt2        ; inv home */
+    INT64_C(0336100001103),                 /* pg:  skipn 2,1103    ; pg of ptrs */
     INT64_C(0254200377033),                 /*      halt .          ; inv ptr */
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0336100001004),                 /*      skipn 2,1004    ; mon boot */
@@ -1270,6 +1273,12 @@ static const d10 boot_rom_dec[] = {
     INT64_C(0602340100000),                 /*      trne 7,100000   ; test err */
     INT64_C(0254200377057),                 /*      halt . */
     INT64_C(0254017000000),                 /*      jrst 0(17)      ; return */
+    INT64_C(0201100000012),                 /*alt2: movei 2,10.     ; blk #10. */
+    INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
+    INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
+    INT64_C(0302140505755),                 /*      caie 3,sixbit /HOM/ */
+    INT64_C(0254200377065),                 /*      halt .          ; inv home */
+    INT64_C(0254000377032),                 /*      jrst pg         ; Read ptrs */
     };
 
 static const d10 boot_rom_its[] = {
@@ -1293,13 +1302,13 @@ static const d10 boot_rom_its[] = {
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
     INT64_C(0306140505755),                 /*      cain 3,sixbit /HOM/ */
-    INT64_C(0254000377032),                 /*      jrst .+6        ; match */
+    INT64_C(0254000377032),                 /*      jrst pg         ; match */
     INT64_C(0201100000010),                 /*      movei 2,10      ; blk #10 */
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
     INT64_C(0302140505755),                 /*      caie 3,sixbit /HOM/ */
-    INT64_C(0254200377031),                 /*      halt .          ; inv home */
-    INT64_C(0336100001103),                 /*      skipn 2,1103    ; pg of ptrs */
+    INT64_C(0254000377061),                 /*      jrst alt2       ; inv home */
+    INT64_C(0336100001103),                 /* pg:  skipn 2,1103    ; pg of ptrs */
     INT64_C(0254200377033),                 /*      halt .          ; inv ptr */
     INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
     INT64_C(0336100001004),                 /*      skipn 2,1004    ; mon boot */
@@ -1322,6 +1331,12 @@ static const d10 boot_rom_its[] = {
     INT64_C(0602340100000),                 /*      trne 7,100000   ; test err */
     INT64_C(0254200377057),                 /*      halt */
     INT64_C(0254017000000),                 /*      jrst 0(17)      ; return */
+    INT64_C(0201100000012),                 /* alt2:movei 2,10.     ; blk #10 */
+    INT64_C(0265740377041),                 /*      jsp 17,rdbl     ; read */
+    INT64_C(0204140001000),                 /*      movs 3,1000     ; id word */
+    INT64_C(0302140505755),                 /*      caie 3,sixbit /HOM/ */
+    INT64_C(0254200377065),                 /*      halt .          ; inv home */
+    INT64_C(0254000377032),                 /*      jrst pg         ; Read ptrs */
     };
 
 t_stat rp_boot (int32 unitno, DEVICE *dptr)
@@ -1337,6 +1352,11 @@ if (!(uptr->flags & UNIT_ATT))
 
 M[FE_RHBASE] = rp_dib.ba;
 M[FE_UNIT] = unitno;
+if (sim_switches & SWMASK ('A'))
+    M[FE_KEEPA] = ((d10) 010);                /* <32>: Autoboot */
+else
+    M[FE_KEEPA] = 0;
+
 for (i = 0; i < BOOT_LEN; i++)
     M[BOOT_START + i] = Q_ITS? boot_rom_its[i]: boot_rom_dec[i];
 saved_PC = BOOT_START;