From df6e888207726b17dd2fdb0a83489bd8be11c2b9 Mon Sep 17 00:00:00 2001
From: Broken Pipe <85091235+TheBrokenPipe@users.noreply.github.com>
Date: Sun, 18 Feb 2024 05:44:23 +0000
Subject: [PATCH] Fixed bugs in boot sector and I/O system

Fixed bugs in the boot sector and BIOS to allow 86-DOS 0.11 to boot using the Tarbell DD floppy controller.
---
 BOOT.ASM  | 12 ++++++++++--
 DOSIO.ASM | 20 ++++++++++----------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/BOOT.ASM b/BOOT.ASM
index d5e4374..ac28247 100644
--- a/BOOT.ASM
+++ b/BOOT.ASM
@@ -82,7 +82,15 @@ SECT:
 	MOV	AL,BL
 	OUTB	DISK+2
 	MOV	CX,128
-	INB	DISK+4
+
+	IF	TARBELL
+	INB	DISK		;Get head load status
+	ENDIF
+
+	IF	CROMEMCO
+	INB	DISK+4		;Get head load status
+	ENDIF
+
 	TEST	AL,20H
 	MOV	AL,READCOM
 	JNZ	OUTCOM
@@ -145,4 +153,4 @@ BOOT:
 	MOV	ES,AX
 	MOV	DS,AX
 	JMP	0,SEG
-
\ No newline at end of file
+
\ No newline at end of file
diff --git a/DOSIO.ASM b/DOSIO.ASM
index f888f7b..0c884b1 100644
--- a/DOSIO.ASM
+++ b/DOSIO.ASM
@@ -278,13 +278,13 @@ PUTSEC:
 	MOV	CX,80H
 
 	IF	TARBELL
-	INB	DISK		;Get head load bit
+	IN	DISK		;Get head load bit
 	ENDIF
 
 	IF	CROMEMCO
-	INB	DISK+4		;Get head load bit
+	IN	DISK+4		;Get head load bit
 	XCHG	AL,AH
-	OUTB	DISK+4		;Turn on auto-wait
+	OUT	DISK+4		;Turn on auto-wait
 	XCHG	AL,AH
 	ENDIF
 
@@ -373,7 +373,7 @@ WRDONE:
 
 HOME:
 	IF	CROMEMCO
-	TEST	AH,10H		;Check seek speed bit
+	TEST	AH,10H		;Check 8" (PerSci) bit
 	JNZ	RESTORE
 	ENDIF
 
@@ -391,7 +391,7 @@ TRYHOM:
 
 MOVHEAD:
 	IF	CROMEMCO
-	TEST	AH,10H		;Check seek speed bit
+	TEST	AH,10H		;Check 8" (PerSci) bit
 	JNZ	FASTSK
 	ENDIF
 
@@ -399,8 +399,8 @@ DCOM:
 	OUT	DISK
 	MOV	AL,50
 DELAY:
-	DEC	AL		;Delay 10 microseconds
-	JNZ	DELAY
+	DEC	AL
+	JNZ	DELAY		;Delay 100 microseconds
 GETSTAT:
 	IN	DISK+4
 	TEST	AL,DONEBIT
@@ -518,7 +518,7 @@ FAT3:	DS	LFAT
 
 ; Cromemco drive select byte is derived as follows:
 ;	Bit 7 = 0
-;	Bit 6 = 1 if fast seek (PerSci)
+;	Bit 6 = X (unassigned)
 ;	Bit 5 = 1 (motor on)
 ;	Bit 4 = 0 for 5", 1 for 8" drives
 ;	Bit 3 = 1 for drive 3
@@ -587,7 +587,7 @@ FAT2:	DS	SFAT
 	ENDIF
 
 	IF	CUSTOM
-; Table for 2 large drives without fast seek
+; Table for 2 large drives
 DRVTAB:	DB	31H,32H
 TRKPT:	DB	0,1
 TRKTAB:	DB	-1,-1
@@ -602,4 +602,4 @@ INITTAB:DB	2
 FAT0:	DS	LFAT
 FAT1:	DS	LFAT
 	ENDIF
-
\ No newline at end of file
+
\ No newline at end of file