From 6dc7309e50c59ca114dfb6500ca786c2a84d13e9 Mon Sep 17 00:00:00 2001
From: Christian Groessler <chris@groessler.org>
Date: Thu, 27 Sep 2018 17:37:59 +0200
Subject: [PATCH] Atari: add support for BW-DOS. Initially contributed by
 Daniel Serpell.

---
 asminc/atari.inc            |  9 +++++----
 include/atari.h             | 11 ++++++-----
 libsrc/atari/dosdetect.s    | 15 +++++++++++++--
 libsrc/atari/lseek.s        |  2 ++
 libsrc/atari/syschdir.s     |  2 ++
 libsrc/atari/system_check.s | 11 ++++++++++-
 6 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/asminc/atari.inc b/asminc/atari.inc
index 4e2958fbc..98c721296 100644
--- a/asminc/atari.inc
+++ b/asminc/atari.inc
@@ -1033,10 +1033,11 @@ diopp_size   = 5        ; size of structure
 
 SPARTADOS    = 0
 REALDOS      = 1
-OSADOS       = 2        ; OS/A+
-XDOS         = 3
-ATARIDOS     = 4
-MYDOS        = 5
+BWDOS        = 2
+OSADOS       = 3        ; OS/A+
+XDOS         = 4
+ATARIDOS     = 5
+MYDOS        = 6
 NODOS        = 255
 ; The DOSes with dos_type below or equal MAX_DOS_WITH_CMDLINE do support
 ; command line arguments.
diff --git a/include/atari.h b/include/atari.h
index d9463904c..ca6bd424c 100644
--- a/include/atari.h
+++ b/include/atari.h
@@ -261,11 +261,12 @@ extern void atrx15p2_tgi[];
 
 /* valid _dos_type values */
 #define SPARTADOS   0
-#define OSADOS      1
-#define XDOS        2
-#define REALDOS     3
-#define ATARIDOS    4
-#define MYDOS       5
+#define REALDOS     1
+#define BWDOS       2
+#define OSADOS      3
+#define XDOS        4
+#define ATARIDOS    5
+#define MYDOS       6
 #define NODOS       255
 
 /* Define hardware */
diff --git a/libsrc/atari/dosdetect.s b/libsrc/atari/dosdetect.s
index 7e6088d97..1dd6a87f5 100644
--- a/libsrc/atari/dosdetect.s
+++ b/libsrc/atari/dosdetect.s
@@ -35,9 +35,20 @@ detect: lda     DOS
         cmp     (DOSVEC),y
         beq     done
         lda     #OSADOS
+        bne     set
+
+spdos:  lda     DOS+3           ; 'B' in BW-DOS
+        cmp     #'B'
+        bne     spdos_real
+        lda     DOS+4           ; 'W' in BW-DOS
+        cmp     #'W'
+        bne     spdos_real
+
+        lda     #BWDOS
         .byte   $2C             ; BIT <abs>
 
-spdos:  lda     #SPARTADOS
+spdos_real:
+        lda     #SPARTADOS
         .byte   $2C             ; BIT <abs>
 
 mydos:  lda     #MYDOS
@@ -47,7 +58,7 @@ rdos:   lda     #REALDOS
         .byte   $2C             ; BIT <abs>
 
 xdos:   lda     #XDOS
-        sta     __dos_type
+set:    sta     __dos_type
 done:   rts
 
 ; ------------------------------------------------------------------------
diff --git a/libsrc/atari/lseek.s b/libsrc/atari/lseek.s
index 462f2f90b..b6a766361 100644
--- a/libsrc/atari/lseek.s
+++ b/libsrc/atari/lseek.s
@@ -195,6 +195,8 @@ chk_supp:
         lda     __dos_type
         cmp     #SPARTADOS
         beq     :+
+        cmp     #BWDOS
+        beq     :+
         cmp     #REALDOS
         bne     ns1
 :       txa
diff --git a/libsrc/atari/syschdir.s b/libsrc/atari/syschdir.s
index 9e4c33a19..f493fea54 100644
--- a/libsrc/atari/syschdir.s
+++ b/libsrc/atari/syschdir.s
@@ -67,6 +67,8 @@ ucok1:
         beq     :+
         cmp     #REALDOS
         beq     :+
+        cmp     #BWDOS
+        beq     :+
         lda     #CHDIR_MYDOS
         .byte   $2C             ; BIT <abs>
 :       lda     #CHDIR_SPDOS
diff --git a/libsrc/atari/system_check.s b/libsrc/atari/system_check.s
index ec0d60513..19efaf2e2 100644
--- a/libsrc/atari/system_check.s
+++ b/libsrc/atari/system_check.s
@@ -77,7 +77,16 @@ cont:   ldx     #0              ; channel 0
 sdcheck:lda     DOS
         cmp     #'S'
         bne     sdcrts0         ; not SpartaDOS, assume RAM is not used
-        lda     DOS+1           ; SD version
+
+; check for BW-DOS, which always reports itself as SpartaDOS, but doesn't use memory under the ROM
+        lda     DOS+3           ; 'B' in BW-DOS
+        cmp     #'B'
+        bne     sdnobw
+        lda     DOS+4           ; 'W' in BW-DOS
+        cmp     #'W'
+        beq     sdcrts0         ; BW-DOS does not use RAM below ROM
+
+sdnobw: lda     DOS+1           ; SD version
         cmp     #$40            ; SD-X has $40 or higher
         bcc     sdcrts1         ; older versions (except maybe 1.x) always use the RAM under the ROM
         ldy     #31             ; offset for OSRMFLG
-- 
2.39.2