From 0516bd1b6afdd6bac4113508fd50d25dda25fd10 Mon Sep 17 00:00:00 2001
From: Mark Pizzolato <mark@infocomm.com>
Date: Mon, 8 Dec 2025 13:29:36 -1000
Subject: [PATCH] B5500, I701, I704, I7010, I7070, I7080, I7090: Remove single
 UNIT DISABLE

If a simh DEVICE has the DEV_DISABLE flag set AND it has 1 UNIT,
there really should never be a UNIT_DISABLE flag bit in the UNIT
initializer.  The reason for this is that, for many things, the DEVICE
name can be used equivalently to represent the single UNIT.
What are we trying to achieve here?

- If the DEVICE is disabled, then the unit doesn't exist.  That's fine.

- If the UNIT is disabled (if the UNIT_DISABLE flag is present allowing
  SET <unit> DISABLE) what would that then mean about the DEVICE?

Bob Supnik's thoughts:

The rationale was that the device represents the controller logic, the
unit the physical transducer. So you could disconnect or power down
a paper tape reader, but its controller logic would still be there and
would still respond in some way.

Mark Pizzolato said:
If the fidelity to the hardware in simulation really behaved precisely
as the hardware worked, maybe, but I doubt that this has been a design
goal.  Even if it had been a design goal, I see 2 issues:
   a) it would seem that it would have been impossible to produce exactly
      the failure details that real hardware did without a crazy amount
      of side by side testing.
   b) What good would be having a broken device like this connected to a
      simulated system?
---
 B5500/b5500_urec.c  | 6 +++---
 I7000/i7000_cdp.c   | 2 +-
 I7000/i7000_cdr.c   | 2 +-
 I7000/i7000_chron.c | 2 +-
 I7000/i7000_dsk.c   | 2 +-
 I7000/i7000_lpr.c   | 2 +-
 I7000/i7000_mt.c    | 2 +-
 I7000/i701_chan.c   | 4 ++--
 I7000/i7080_drum.c  | 2 +-
 I7000/i7090_cdp.c   | 2 +-
 I7000/i7090_cdr.c   | 2 +-
 I7000/i7090_chan.c  | 4 ++--
 I7000/i7090_drum.c  | 2 +-
 I7000/i7090_hdrum.c | 2 +-
 I7000/i7090_lpr.c   | 2 +-
 PDP10/ka10_pclk.c   | 2 +-
 PDP10/ka10_pd.c     | 2 +-
 PDP10/ka10_stk.c    | 2 +-
 PDP10/ks10_dz.c     | 2 +-
 PDP10/ks10_tcu.c    | 2 +-
 PDP10/kx10_cp.c     | 2 +-
 PDP10/kx10_cr.c     | 2 +-
 PDP10/kx10_dc.c     | 2 +-
 23 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/B5500/b5500_urec.c b/B5500/b5500_urec.c
index 6efc96b0..49bf3a76 100644
--- a/B5500/b5500_urec.c
+++ b/B5500/b5500_urec.c
@@ -31,9 +31,9 @@
 #include "sim_defs.h"
 #include "sim_console.h"
 
-#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | UNIT_DISABLE | MODE_029
-#define UNIT_CDP        UNIT_ATTABLE | UNIT_SEQ | UNIT_DISABLE | MODE_029
-#define UNIT_LPR        UNIT_ATTABLE | UNIT_SEQ | UNIT_DISABLE
+#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | ((NUM_DEVS_CDR > 1) ? UNIT_DISABLE : 0) | MODE_029
+#define UNIT_CDP        UNIT_ATTABLE | UNIT_SEQ | ((NUM_DEVS_CDP > 1) ? UNIT_DISABLE : 0) | MODE_029
+#define UNIT_LPR        UNIT_ATTABLE | UNIT_SEQ | ((NUM_DEVS_LPR > 1) ? UNIT_DISABLE : 0)
 
 #define TMR_RTC         0
 
diff --git a/I7000/i7000_cdp.c b/I7000/i7000_cdp.c
index 873a89fa..4cc986e4 100644
--- a/I7000/i7000_cdp.c
+++ b/I7000/i7000_cdp.c
@@ -34,7 +34,7 @@
 #include "sim_defs.h"
 #ifdef NUM_DEVS_CDP
 
-#define UNIT_CDP        UNIT_ATTABLE | UNIT_DISABLE | UNIT_SEQ | MODE_026
+#define UNIT_CDP        UNIT_ATTABLE | ((NUM_DEVS_CDP > 1) ? UNIT_DISABLE : 0) | UNIT_SEQ | MODE_026
 
 
 /* Flags for punch and reader. */
diff --git a/I7000/i7000_cdr.c b/I7000/i7000_cdr.c
index 093b864e..ef8c1f01 100644
--- a/I7000/i7000_cdr.c
+++ b/I7000/i7000_cdr.c
@@ -34,7 +34,7 @@
 #include "sim_defs.h"
 #ifdef NUM_DEVS_CDR
 
-#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | UNIT_DISABLE | MODE_026
+#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | ((NUM_DEVS_CDR > 1) ? UNIT_DISABLE : 0) | MODE_026
 
 /* Flags for punch and reader. */
 #define ATTENA          (1 << (UNIT_V_UF+7))
diff --git a/I7000/i7000_chron.c b/I7000/i7000_chron.c
index b60a2354..88e4b9cb 100644
--- a/I7000/i7000_chron.c
+++ b/I7000/i7000_chron.c
@@ -27,7 +27,7 @@
 #ifdef NUM_DEVS_CHRON
 #define BUFFSIZE        (12)
 
-#define UNIT_MT(x)      UNIT_DISABLE | UNIT_ROABLE | \
+#define UNIT_MT(x)      ((NUM_DEVS_CHRON > 1) ? UNIT_DISABLE : 0) | UNIT_ROABLE | \
                         UNIT_S_CHAN(x)
 
 /* in u3 is device address */
diff --git a/I7000/i7000_dsk.c b/I7000/i7000_dsk.c
index fa7f307f..f9745fca 100644
--- a/I7000/i7000_dsk.c
+++ b/I7000/i7000_dsk.c
@@ -47,7 +47,7 @@
 #include "i7000_defs.h"
 
 #ifdef NUM_DEVS_DSK
-#define UNIT_DSK        UNIT_ATTABLE | UNIT_DISABLE | UNIT_FIX
+#define UNIT_DSK        UNIT_ATTABLE | ((NUM_DEVS_DSK > 1) ? UNIT_DISABLE : 0) | UNIT_FIX
 #define FORMAT_OK       (1 << (UNIT_V_LOCAL+0))
 #define HA2_OK          (1 << (UNIT_V_LOCAL+1))
 #define CTSS_BOOT       (1 << (UNIT_V_MODE))
diff --git a/I7000/i7000_lpr.c b/I7000/i7000_lpr.c
index 08b807c4..ce7cc905 100644
--- a/I7000/i7000_lpr.c
+++ b/I7000/i7000_lpr.c
@@ -34,7 +34,7 @@
 #include "sim_defs.h"
 #ifdef NUM_DEVS_LPR
 
-#define UNIT_LPR        UNIT_ATTABLE | UNIT_DISABLE | UNIT_SEQ
+#define UNIT_LPR        UNIT_ATTABLE | ((NUM_DEVS_LPR > 1) ? UNIT_DISABLE : 0) | UNIT_SEQ
 
 
 /* Flags for line printer. */
diff --git a/I7000/i7000_mt.c b/I7000/i7000_mt.c
index 0fc7f29b..63c96966 100644
--- a/I7000/i7000_mt.c
+++ b/I7000/i7000_mt.c
@@ -44,7 +44,7 @@
 #if (NUM_DEVS_MT > 0) || defined(MT_CHANNEL_ZERO)
 
 #define BUFFSIZE        (MAXMEMSIZE * CHARSPERWORD)
-#define UNIT_MT(x)      UNIT_ATTABLE | UNIT_DISABLE | UNIT_ROABLE | \
+#define UNIT_MT(x)      UNIT_ATTABLE | ((NUM_DEVS_MT > 1) ? UNIT_DISABLE : 0) | UNIT_ROABLE | \
                         UNIT_S_CHAN(x)
 #define MTUF_LDN        (1 << MTUF_V_UF)
 #define MTUF_ONLINE     (1 << UNIT_V_UF_31)
diff --git a/I7000/i701_chan.c b/I7000/i701_chan.c
index 9f9aa2bb..a4dd2e3e 100644
--- a/I7000/i701_chan.c
+++ b/I7000/i701_chan.c
@@ -65,7 +65,7 @@ DIB                 dly_dib =
 
 UNIT                chan_unit[] = {
     /* Puesdo channel for 701 devices */
-    {UDATA(NULL, UNIT_DISABLE | CHAN_SET |
+    {UDATA(NULL, CHAN_SET |
                         CHAN_S_TYPE(CHAN_PIO)|UNIT_S_CHAN(0), 0)},
 };
 
@@ -85,7 +85,7 @@ DEVICE              chan_dev = {
     "CH", chan_unit, chan_reg, chan_mod,
     NUM_CHAN, 8, 15, 1, 8, 36,
     NULL, NULL, &chan_reset, NULL, NULL, NULL,
-    &dly_dib, DEV_DEBUG, 0, NULL,
+    &dly_dib, DEV_DISABLE | DEV_DEBUG, 0, NULL,
     NULL, NULL, &chan_help, NULL, NULL, &chan_description
 };
 
diff --git a/I7000/i7080_drum.c b/I7000/i7080_drum.c
index bcc0183a..2859a79d 100644
--- a/I7000/i7080_drum.c
+++ b/I7000/i7080_drum.c
@@ -36,7 +36,7 @@
 #include "i7080_defs.h"
 
 #ifdef NUM_DEVS_DR
-#define UNIT_DRM        UNIT_ATTABLE | UNIT_DISABLE | UNIT_FIX | \
+#define UNIT_DRM        UNIT_ATTABLE | ((NUM_DEVS_DR > 1) ? UNIT_DISABLE : 0) | UNIT_FIX | \
                         UNIT_BUFABLE | UNIT_MUSTBUF
 
 /* Device status information stored in u5 */
diff --git a/I7000/i7090_cdp.c b/I7000/i7090_cdp.c
index 9fce8eab..e749bf68 100644
--- a/I7000/i7090_cdp.c
+++ b/I7000/i7090_cdp.c
@@ -26,7 +26,7 @@
 #include "i7090_defs.h"
 #include "sim_card.h"
 #ifdef NUM_DEVS_CDP
-#define UNIT_CDP        UNIT_ATTABLE | UNIT_DISABLE | UNIT_SEQ
+#define UNIT_CDP        UNIT_ATTABLE | ((NUM_DEVS_CDP > 1) ? UNIT_DISABLE : 0) | UNIT_SEQ
 
 
 /* std devices. data structures
diff --git a/I7000/i7090_cdr.c b/I7000/i7090_cdr.c
index e075646c..7dd65201 100644
--- a/I7000/i7090_cdr.c
+++ b/I7000/i7090_cdr.c
@@ -28,7 +28,7 @@
 
 #ifdef NUM_DEVS_CDR
 
-#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | UNIT_DISABLE | MODE_026
+#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | ((NUM_DEVS_CDR > 1) ? UNIT_DISABLE : 0) | MODE_026
 
 
 /* std devices. data structures
diff --git a/I7000/i7090_chan.c b/I7000/i7090_chan.c
index 71ea9065..14832795 100644
--- a/I7000/i7090_chan.c
+++ b/I7000/i7090_chan.c
@@ -148,7 +148,7 @@ DIB                 dly_dib =
 
 UNIT                chan_unit[] = {
     /* Puesdo channel for 704 devices */
-    {UDATA(NULL, UNIT_DISABLE | CHAN_SET |
+    {UDATA(NULL, ((NUM_CHAN > 1) ? UNIT_DISABLE : 0) | CHAN_SET |
                         CHAN_S_TYPE(CHAN_PIO)|UNIT_S_CHAN(0), 0)},
     /* Normal channels */
 #if NUM_CHAN > 1
@@ -215,7 +215,7 @@ DEVICE              chan_dev = {
     "CH", chan_unit, chan_reg, chan_mod,
     NUM_CHAN, 8, 15, 1, 8, 36,
     NULL, NULL, &chan_reset, NULL, NULL, NULL,
-    &dly_dib, DEV_DEBUG, 0, chn_debug,
+    &dly_dib, DEV_DISABLE | DEV_DEBUG, 0, chn_debug,
     NULL, NULL, &chan_help, NULL, NULL, &chan_description
 };
 
diff --git a/I7000/i7090_drum.c b/I7000/i7090_drum.c
index 9385b103..e4627d2f 100644
--- a/I7000/i7090_drum.c
+++ b/I7000/i7090_drum.c
@@ -26,7 +26,7 @@
 #include "i7090_defs.h"
 
 #ifdef NUM_DEVS_DR
-#define UNIT_DRM        UNIT_ATTABLE | UNIT_DISABLE | UNIT_FIX | \
+#define UNIT_DRM        UNIT_ATTABLE | ((NUM_DEVS_DR > 1) ? UNIT_DISABLE : 0) | UNIT_FIX | \
                         UNIT_BUFABLE | UNIT_MUSTBUF
 
 /* Device status information stored in u5 */
diff --git a/I7000/i7090_hdrum.c b/I7000/i7090_hdrum.c
index f52461b9..627a3a9f 100644
--- a/I7000/i7090_hdrum.c
+++ b/I7000/i7090_hdrum.c
@@ -26,7 +26,7 @@
 #include "i7090_defs.h"
 
 #ifdef NUM_DEVS_HD
-#define UNIT_DRM        UNIT_ATTABLE | UNIT_DISABLE | UNIT_FIX | \
+#define UNIT_DRM        UNIT_ATTABLE | ((NUM_DEVS_HD > 1) ? UNIT_DISABLE : 0) | UNIT_FIX | \
                         UNIT_BUFABLE | UNIT_MUSTBUF
 
 /* Device status information stored in u5 */
diff --git a/I7000/i7090_lpr.c b/I7000/i7090_lpr.c
index f614aa5b..c9b0b145 100644
--- a/I7000/i7090_lpr.c
+++ b/I7000/i7090_lpr.c
@@ -40,7 +40,7 @@
 
 #ifdef NUM_DEVS_LPR
 
-#define UNIT_LPR        UNIT_ATTABLE | UNIT_DISABLE | UNIT_SEQ
+#define UNIT_LPR        UNIT_ATTABLE | ((NUM_DEVS_LPR > 1) ? UNIT_DISABLE : 0) | UNIT_SEQ
 #define ECHO            (1 << UNIT_V_LOCAL)
 
 
diff --git a/PDP10/ka10_pclk.c b/PDP10/ka10_pclk.c
index a3981b3a..aaafcdd3 100644
--- a/PDP10/ka10_pclk.c
+++ b/PDP10/ka10_pclk.c
@@ -44,7 +44,7 @@ t_stat         pclk_set_off(UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 t_stat         pclk_show_on(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 
 UNIT pclk_unit[] = {
-    {UDATA(pclk_srv, UNIT_IDLE|UNIT_DISABLE, 0)},  /* 0 */
+    {UDATA(pclk_srv, UNIT_IDLE, 0)},  /* 0 */
 };
 DIB pclk_dib = {PCLK_DEVNUM, 1, &pclk_devio, NULL};
 MTAB pclk_mod[] = {
diff --git a/PDP10/ka10_pd.c b/PDP10/ka10_pd.c
index 3c3b046b..f53274c6 100644
--- a/PDP10/ka10_pd.c
+++ b/PDP10/ka10_pd.c
@@ -56,7 +56,7 @@ t_stat         pd_set_off(UNIT *uptr, int32 val, CONST char *cptr, void *desc);
 t_stat         pd_show_on(FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 
 UNIT                pd_unit[] = {
-    {UDATA(pd_srv, UNIT_IDLE|UNIT_DISABLE, 0)},  /* 0 */
+    {UDATA(pd_srv, UNIT_IDLE, 0)},  /* 0 */
 };
 DIB pd_dib = {PD_DEVNUM, 1, &pd_devio, NULL};
 
diff --git a/PDP10/ka10_stk.c b/PDP10/ka10_stk.c
index 4c965ec0..2f36d955 100644
--- a/PDP10/ka10_stk.c
+++ b/PDP10/ka10_stk.c
@@ -52,7 +52,7 @@ static uint64 status = 0;
 static int key_code = 0;
 
 UNIT                stk_unit[] = {
-    {UDATA(stk_svc, UNIT_DISABLE, 0)},  /* 0 */
+    {UDATA(stk_svc, 0, 0)},  /* 0 */
 };
 DIB stk_dib = {STK_DEVNUM, 1, &stk_devio, NULL};
 
diff --git a/PDP10/ks10_dz.c b/PDP10/ks10_dz.c
index 27055344..8db30957 100644
--- a/PDP10/ks10_dz.c
+++ b/PDP10/ks10_dz.c
@@ -127,7 +127,7 @@ const char *dz_description (DEVICE *dptr);
 DIB dz_dib = { 0760000, 077, 0340, 5, 3, &dz_read, &dz_write, 0, 0, 0 };
 
 UNIT dz_unit = {
-    UDATA (&dz_svc, TT_MODE_7B+UNIT_IDLE+UNIT_DISABLE+UNIT_ATTABLE, 0), KBD_POLL_WAIT
+    UDATA (&dz_svc, TT_MODE_7B+UNIT_IDLE+UNIT_ATTABLE, 0), KBD_POLL_WAIT
     };
 
 REG dz_reg[] = {
diff --git a/PDP10/ks10_tcu.c b/PDP10/ks10_tcu.c
index 3ceac502..10045c54 100644
--- a/PDP10/ks10_tcu.c
+++ b/PDP10/ks10_tcu.c
@@ -46,7 +46,7 @@ t_stat tcu_help (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag,
 const char *tcu_description (DEVICE *dptr);
 DIB tcu_dib = { 0760770, 07, 0, 0, 3, &tcu_read, &tcu_write, NULL, 0, 0 };
 
-UNIT tcu_unit = {UDATA (NULL, UNIT_IDLE+UNIT_DISABLE, 0)};
+UNIT tcu_unit = {UDATA (NULL, UNIT_IDLE, 0)};
 
 MTAB tcu_mod[] = {
     {MTAB_XTD|MTAB_VDV|MTAB_VALR, 0, "addr", "addr",  &uba_set_addr, uba_show_addr,
diff --git a/PDP10/kx10_cp.c b/PDP10/kx10_cp.c
index 34e9014c..3f7420b8 100644
--- a/PDP10/kx10_cp.c
+++ b/PDP10/kx10_cp.c
@@ -34,7 +34,7 @@
 #include "sim_defs.h"
 #if (NUM_DEVS_CP > 0)
 
-#define UNIT_CDP        UNIT_ATTABLE | UNIT_DISABLE | UNIT_SEQ | MODE_DEC29 
+#define UNIT_CDP        UNIT_ATTABLE | UNIT_SEQ | MODE_DEC29 
 
 #define CP_DEVNUM        0110
 
diff --git a/PDP10/kx10_cr.c b/PDP10/kx10_cr.c
index 8bf5c306..80fa864b 100644
--- a/PDP10/kx10_cr.c
+++ b/PDP10/kx10_cr.c
@@ -34,7 +34,7 @@
 #include "sim_defs.h"
 #if (NUM_DEVS_CR > 0)
 
-#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | UNIT_DISABLE | MODE_DEC29 | MODE_LOWER
+#define UNIT_CDR        UNIT_ATTABLE | UNIT_RO | MODE_DEC29 | MODE_LOWER
 
 #define CR_DEVNUM        0150
 
diff --git a/PDP10/kx10_dc.c b/PDP10/kx10_dc.c
index 15124c3d..08937126 100644
--- a/PDP10/kx10_dc.c
+++ b/PDP10/kx10_dc.c
@@ -115,7 +115,7 @@ const char *dc_description (DEVICE *dptr);
 DIB dc_dib = { DC_DEVNUM, 1, &dc_devio, NULL };
 
 UNIT dc_unit = {
-    UDATA (&dc_svc, TT_MODE_7B+UNIT_IDLE+UNIT_DISABLE+UNIT_ATTABLE, 0), KBD_POLL_WAIT
+    UDATA (&dc_svc, TT_MODE_7B+UNIT_IDLE+UNIT_ATTABLE, 0), KBD_POLL_WAIT
     };
 
 REG dc_reg[] = {