diff --git a/Doc/ChangeLog.txt b/Doc/ChangeLog.txt
index 8d28bd22..e177cbc8 100644
--- a/Doc/ChangeLog.txt
+++ b/Doc/ChangeLog.txt
@@ -6,6 +6,7 @@ Version 3.1
 - WBW: Added support dual 16C550 UART on RC2014 platform
 - WBW: Made .com images smaller (contain only Z-System now)
 - WBW: Support automatic clock hardware detection and fallback
+- WBW: Support use of CTC for SIO baud rate divisors
 
 Version 3.0.1
 -------------
diff --git a/Doc/RomWBW Applications.pdf b/Doc/RomWBW Applications.pdf
index ed1cd38b..4fdbaee4 100644
Binary files a/Doc/RomWBW Applications.pdf and b/Doc/RomWBW Applications.pdf differ
diff --git a/Doc/RomWBW Architecture.pdf b/Doc/RomWBW Architecture.pdf
index 10bbc123..3987650c 100644
Binary files a/Doc/RomWBW Architecture.pdf and b/Doc/RomWBW Architecture.pdf differ
diff --git a/Doc/RomWBW Getting Started.pdf b/Doc/RomWBW Getting Started.pdf
index dabf18a4..2329e301 100644
Binary files a/Doc/RomWBW Getting Started.pdf and b/Doc/RomWBW Getting Started.pdf differ
diff --git a/ReadMe.md b/ReadMe.md
index 8c4346c4..030e20e5 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -3,7 +3,7 @@
 ## Z80/Z180 System Software
 
 Version 3.1 Pre-release  
-Saturday 11 April 2020
+Wednesday 15 April 2020
 
 Wayne Warthen <wwarthen@gmail.com>
 
@@ -311,7 +311,7 @@ media. You can think of slices as a way to refer to any of the first 256
 Of course, the problem is that CP/M-like operating systems have only 16
 drive letters (A:-P:) available. Under the covers, RomWBW allows you to
 use any drive letter to refer to any slice of any media. The `ASSIGN`
-command is allows you to view or change the drive letter mappings at any
+command allows you to view or change the drive letter mappings at any
 time. At startup, the operating system will automatically allocate a
 reasonable number of drive letters to the available storage devices. The
 allocation will depend on the number of large storage devices available
diff --git a/ReadMe.txt b/ReadMe.txt
index f47dcf47..e0241d40 100644
--- a/ReadMe.txt
+++ b/ReadMe.txt
@@ -3,7 +3,7 @@ RomWBW
 Z80/Z180 System Software
 
 Version 3.1 Pre-release
-Saturday 11 April 2020
+Wednesday 15 April 2020
 
 Wayne Warthen wwarthen@gmail.com
 
@@ -325,7 +325,7 @@ media. You can think of slices as a way to refer to any of the first 256
 Of course, the problem is that CP/M-like operating systems have only 16
 drive letters (A:-P:) available. Under the covers, RomWBW allows you to
 use any drive letter to refer to any slice of any media. The ASSIGN
-command is allows you to view or change the drive letter mappings at any
+command allows you to view or change the drive letter mappings at any
 time. At startup, the operating system will automatically allocate a
 reasonable number of drive letters to the available storage devices. The
 allocation will depend on the number of large storage devices available
diff --git a/Source/Doc/GettingStarted.md b/Source/Doc/GettingStarted.md
index 345c768b..a92b189a 100644
--- a/Source/Doc/GettingStarted.md
+++ b/Source/Doc/GettingStarted.md
@@ -346,7 +346,7 @@ the first 256 8MB chunks of space on a single media.
 Of course, the problem is that CP/M-like operating systems have only
 16 drive letters (A:-P:) available. Under the covers, RomWBW allows
 you to use any drive letter to refer to any slice of any media. The
-`ASSIGN` command is allows you to view or change the drive letter
+`ASSIGN` command allows you to view or change the drive letter
 mappings at any time. At startup, the operating system will
 automatically allocate a reasonable number of drive letters to the
 available storage devices. The allocation will depend on the number of
diff --git a/Source/HBIOS/Config/RCZ80_kio.asm b/Source/HBIOS/Config/RCZ80_kio.asm
index a83052f4..91ef5e73 100644
--- a/Source/HBIOS/Config/RCZ80_kio.asm
+++ b/Source/HBIOS/Config/RCZ80_kio.asm
@@ -39,8 +39,9 @@ ACIAENABLE	.SET	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 ;
 SIOENABLE	.SET	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIOCNT		.SET	1		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.SET	SIOMODE_EZZ80	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
+SIO0MODE	.SET	SIOMODE_STD	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.SET	KIOBASE+$08	; SIO 0: REGISTERS BASE ADR
-SIO0CTCC	.SET	0		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0ACLK	.SET	1843200		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
+SIO0ACTCC	.SET	0		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.SET	1843200		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
+SIO0BCTCC	.SET	1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
diff --git a/Source/HBIOS/cfg_ezz80.asm b/Source/HBIOS/cfg_ezz80.asm
index 1c64c652..b7a190f8 100644
--- a/Source/HBIOS/cfg_ezz80.asm
+++ b/Source/HBIOS/cfg_ezz80.asm
@@ -86,24 +86,22 @@ ACIAENABLE	.EQU	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	2		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_EZZ80	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0MODE	.EQU	SIOMODE_STD	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.EQU	$80		; SIO 0: REGISTERS BASE ADR
 SIO0ACLK	.EQU	1843200		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	1		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0ACFG	.EQU	DEFSERCFG	; SIO 0A: SERIAL LINE CONFIG
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.EQU	1843200		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	1		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0BCFG	.EQU	DEFSERCFG	; SIO 0B: SERIAL LINE CONFIG
-SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO1CTCC	.EQU	-1		; SIO 1: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO1BASE	.EQU	$84		; SIO 1: REGISTERS BASE ADR
 SIO1ACLK	.EQU	7372800		; SIO 1A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1ADIV	.EQU	1		; SIO 1A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1ACFG	.EQU	DEFSERCFG	; SIO 1A: SERIAL LINE CONFIG
+SIO1ACTCC	.EQU	-1		; SIO 1A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO1BCLK	.EQU	7372800		; SIO 1B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1BDIV	.EQU	1		; SIO 1B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1BCFG	.EQU	DEFSERCFG	; SIO 1B: SERIAL LINE CONFIG
+SIO1BCTCC	.EQU	-1		; SIO 1B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index 55806745..b5f4ce33 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -121,24 +121,22 @@ ACIA1CFG	.EQU	DEFSERCFG	; ACIA 1: SERIAL LINE CONFIG  (SEE STD.ASM)
 SIOENABLE	.EQU	FALSE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	2		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.EQU	$80		; SIO 0: REGISTERS BASE ADR
 SIO0ACLK	.EQU	CPUOSC		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	1		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0ACFG	.EQU	DEFSERCFG	; SIO 0A: SERIAL LINE CONFIG
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.EQU	CPUOSC		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	1		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0BCFG	.EQU	DEFSERCFG	; SIO 0B: SERIAL LINE CONFIG
-SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO1CTCC	.EQU	-1		; SIO 1: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO1BASE	.EQU	$84		; SIO 1: REGISTERS BASE ADR
 SIO1ACLK	.EQU	CPUOSC		; SIO 1A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1ADIV	.EQU	1		; SIO 1A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1ACFG	.EQU	DEFSERCFG	; SIO 1A: SERIAL LINE CONFIG
+SIO1ACTCC	.EQU	-1		; SIO 1A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO1BCLK	.EQU	CPUOSC		; SIO 1B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1BDIV	.EQU	1		; SIO 1B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1BCFG	.EQU	DEFSERCFG	; SIO 1B: SERIAL LINE CONFIG
+SIO1BCTCC	.EQU	-1		; SIO 1B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_rcz180.asm b/Source/HBIOS/cfg_rcz180.asm
index ee65373f..746446f2 100644
--- a/Source/HBIOS/cfg_rcz180.asm
+++ b/Source/HBIOS/cfg_rcz180.asm
@@ -91,24 +91,22 @@ ACIAENABLE	.EQU	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	2		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.EQU	$80		; SIO 0: REGISTERS BASE ADR
 SIO0ACLK	.EQU	7372800		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	1		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0ACFG	.EQU	SER_115200_8N1	; SER_115200_8N1 0A: SERIAL LINE CONFIG
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.EQU	7372800		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	1		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0BCFG	.EQU	SER_115200_8N1	; SIO 0B: SERIAL LINE CONFIG
-SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO1CTCC	.EQU	-1		; SIO 1: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO1BASE	.EQU	$84		; SIO 1: REGISTERS BASE ADR
 SIO1ACLK	.EQU	7372800		; SIO 1A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1ADIV	.EQU	1		; SIO 1A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1ACFG	.EQU	SER_115200_8N1	; SER_115200_8N1 1A: SERIAL LINE CONFIG
+SIO1ACTCC	.EQU	-1		; SIO 1A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO1BCLK	.EQU	7372800		; SIO 1B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1BDIV	.EQU	1		; SIO 1B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1BCFG	.EQU	SER_115200_8N1	; SIO 1B: SERIAL LINE CONFIG
+SIO1BCTCC	.EQU	-1		; SIO 1B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_rcz80.asm b/Source/HBIOS/cfg_rcz80.asm
index 40b3d129..971216b3 100644
--- a/Source/HBIOS/cfg_rcz80.asm
+++ b/Source/HBIOS/cfg_rcz80.asm
@@ -95,24 +95,22 @@ ACIA1CFG	.EQU	DEFSERCFG	; ACIA 1: SERIAL LINE CONFIG  (SEE STD.ASM)
 SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	2		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.EQU	$80		; SIO 0: REGISTERS BASE ADR
 SIO0ACLK	.EQU	CPUOSC		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	1		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0ACFG	.EQU	DEFSERCFG	; SIO 0A: SERIAL LINE CONFIG
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.EQU	CPUOSC		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	1		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0BCFG	.EQU	DEFSERCFG	; SIO 0B: SERIAL LINE CONFIG
-SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO1CTCC	.EQU	-1		; SIO 1: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO1BASE	.EQU	$84		; SIO 1: REGISTERS BASE ADR
 SIO1ACLK	.EQU	CPUOSC		; SIO 1A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1ADIV	.EQU	1		; SIO 1A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1ACFG	.EQU	DEFSERCFG	; SIO 1A: SERIAL LINE CONFIG
+SIO1ACTCC	.EQU	-1		; SIO 1A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO1BCLK	.EQU	CPUOSC		; SIO 1B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1BDIV	.EQU	1		; SIO 1B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1BCFG	.EQU	DEFSERCFG	; SIO 1B: SERIAL LINE CONFIG
+SIO1BCTCC	.EQU	-1		; SIO 1B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index e451213d..0121cce9 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -88,15 +88,15 @@ ACIAENABLE	.EQU	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	1		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_ZP	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
+SIO0MODE	.EQU	SIOMODE_ZP	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BASE	.EQU	$B0		; SIO 0: REGISTERS BASE ADR
-SIO0ACLK	.EQU	4915200		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	8		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
+SIO0ACLK	.EQU	(4915200/8)	; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
 SIO0ACFG	.EQU	DEFSERCFG	; SIO 0A: SERIAL LINE CONFIG
-SIO0BCLK	.EQU	4915200		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	8		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCLK	.EQU	(4915200/8)	; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
 SIO0BCFG	.EQU	DEFSERCFG	; SIO 0B: SERIAL LINE CONFIG
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_scz180.asm b/Source/HBIOS/cfg_scz180.asm
index a92c4105..cc92824b 100644
--- a/Source/HBIOS/cfg_scz180.asm
+++ b/Source/HBIOS/cfg_scz180.asm
@@ -86,24 +86,22 @@ ACIAENABLE	.EQU	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOCNT		.EQU	2		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
-SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO0CTCC	.EQU	-1		; SIO 0: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0MODE	.EQU	SIOMODE_RC	; SIO 0: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO0BASE	.EQU	$80		; SIO 0: REGISTERS BASE ADR
 SIO0ACLK	.EQU	7372800		; SIO 0A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0ADIV	.EQU	1		; SIO 0A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0ACFG	.EQU	SER_115200_8N1	; SIO 0A: SERIAL LINE CONFIG
+SIO0ACTCC	.EQU	-1		; SIO 0A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO0BCLK	.EQU	7372800		; SIO 0B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO0BDIV	.EQU	1		; SIO 0B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO0BCFG	.EQU	SER_115200_8N1	; SIO 0B: SERIAL LINE CONFIG
-SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[RC|SMB|ZP|EZZ80]
-SIO1CTCC	.EQU	-1		; SIO 1: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO0BCTCC	.EQU	-1		; SIO 0B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
+SIO1MODE	.EQU	SIOMODE_RC	; SIO 1: CHIP TYPE: SIOMODE_[STD|RC|SMB|ZP]
 SIO1BASE	.EQU	$84		; SIO 1: REGISTERS BASE ADR
 SIO1ACLK	.EQU	7372800		; SIO 1A: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1ADIV	.EQU	1		; SIO 1A: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1ACFG	.EQU	SER_115200_8N1	; SIO 1A: SERIAL LINE CONFIG
+SIO1ACTCC	.EQU	-1		; SIO 1A: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 SIO1BCLK	.EQU	7372800		; SIO 1B: OSC FREQ IN HZ, ZP=2457600/4915200, RC/SMB=7372800
-SIO1BDIV	.EQU	1		; SIO 1B: SERIAL CLOCK DIVIDER, RC2014/SMB=1, ZP=2/4/8/16/32/64/128/256 (X5)
 SIO1BCFG	.EQU	SER_115200_8N1	; SIO 1B: SERIAL LINE CONFIG
+SIO1BCTCC	.EQU	-1		; SIO 1B: CTC CHANNEL CLOCK SCALER, (0-3), -1 FOR NONE
 ;
 XIOCFG		.EQU	DEFSERCFG	; XIO: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/sd.asm b/Source/HBIOS/sd.asm
index b0b2e379..ef187081 100644
--- a/Source/HBIOS/sd.asm
+++ b/Source/HBIOS/sd.asm
@@ -41,7 +41,7 @@
 ;      THE CLOCK IS LOW. THE DATA IS CAPTURED ON THE CLOCK'S LOW-TO-HIGH
 ;      TRANSITION AND PROPAGATED ON HIGH-TO-LOW CLOCK TRANSITION.
 ;
-;      NOTE: THE CSIO IMPLEMENTATION (INCLUDE MK4) USES SPI MODE 4
+;      NOTE: THE CSIO IMPLEMENTATION (INCLUDE MK4) USES SPI MODE 3
 ;      (CPOL=1, CPHA=1) BECAUSE THAT IS THE WAY THAT THE Z180 CSIO
 ;      INTERFACE WORKS.	 ALL OF THE CLOCK TRANSITIONS LISTED ABOVE
 ;      ARE REVERSED FOR CSIO.
@@ -104,7 +104,7 @@
 ;      IS FLOATING IT IS IMPOSSIBLE TO DETERMINE IF THE BYTE RECEIVED IS A FILL
 ;      BYTE OR NOT.  BASED ON WHAT I HAVE READ, THERE WILL ALWAYS BE AT LEAST
 ;      ONE FILL BYTE PRIOR TO THE ACTUAL RESULT.  ADDITIONALLY, THE SD CARD WILL
-;      START DRIVING MISO SOMETIME WITHING THAT FIRST FILL BYTE.  SO, WE NOW
+;      START DRIVING MISO SOMETIME WITHIN THAT FIRST FILL BYTE.  SO, WE NOW
 ;      JUST DISCARD THE FIRST BYTE RECEIVED AFTER A COMMAND IS SENT WITH THE
 ;      ASSUMPTION THAT IT MUST BE A FILL BYTE AND IS NOT RELIABLE DUE TO FLOATING
 ;      MISO.
@@ -1025,6 +1025,7 @@ SD_INITCARD5:
 	; PER SPEC, THE CARD SHOULD NOW BE ABLE TO HANDLE FULL SPEED OPERATION
 	; SO, FOR CSIO OPERATION, WE SET CSIO TO MAXIMUM SPEED
 	CALL	SD_WAITTX		; MAKE SURE WE ARE DONE SENDING
+	CALL	DLY4			; WAIT A BIT MORE FOR FINAL BIT
 	XOR	A			; ZERO MEANS MAX SPEED
 	OUT	(Z180_CNTR),A		; NOW SET CSIO PORT
 #ENDIF
@@ -1703,19 +1704,19 @@ SD_DESELECT:
 ;
 ; CSIO WAIT FOR TRANSMIT READY (TX REGSITER EMPTY)
 ;
-SD_WAITTX:				; WAIT FOR TX EMPTY
+SD_WAITTX:
 	IN0	A,(SD_CNTR)		; GET CSIO STATUS
 	BIT	4,A			; TX EMPTY?
-	JR	NZ,SD_WAITTX
-	RET
+	JR	NZ,SD_WAITTX		; LOOP WHILE BUSY
+	RET				; DONE
 ;
 ; CSIO WAIT FOR RECEIVER READY (BYTE AVAILABLE)
 ;
 SD_WAITRX:
 	IN0	A,(SD_CNTR)		; WAIT FOR RECEIVER TO FINISH
-	BIT	5,A
-	JR	NZ,SD_WAITRX
-	RET
+	BIT	5,A			; RX EMPTY?
+	JR	NZ,SD_WAITRX		; LOOP WHILE BUSY
+	RET				; DONE
 ;
 #ENDIF
 ;
diff --git a/Source/HBIOS/sio.asm b/Source/HBIOS/sio.asm
index 31000849..ae4129df 100644
--- a/Source/HBIOS/sio.asm
+++ b/Source/HBIOS/sio.asm
@@ -39,6 +39,13 @@ SIO1_VEC	.EQU	VEC(INT_SIO1)
 ;
 #ENDIF
 ;
+#IF (SIO0MODE == SIOMODE_STD)
+SIO0A_CMD	.EQU	SIO0BASE + $01	
+SIO0A_DAT	.EQU	SIO0BASE + $00
+SIO0B_CMD	.EQU	SIO0BASE + $03
+SIO0B_DAT	.EQU	SIO0BASE + $02
+#ENDIF
+;
 #IF (SIO0MODE == SIOMODE_RC)
 SIO0A_CMD	.EQU	SIO0BASE + $00	
 SIO0A_DAT	.EQU	SIO0BASE + $01
@@ -60,15 +67,15 @@ SIO0B_CMD	.EQU	SIO0BASE + $07
 SIO0B_DAT	.EQU	SIO0BASE + $05
 #ENDIF
 ;
-#IF (SIO0MODE == SIOMODE_EZZ80)
-SIO0A_CMD	.EQU	SIO0BASE + $01	
-SIO0A_DAT	.EQU	SIO0BASE + $00
-SIO0B_CMD	.EQU	SIO0BASE + $03
-SIO0B_DAT	.EQU	SIO0BASE + $02
-#ENDIF
-;
 #IF (SIOCNT >= 2)
 ;
+#IF (SIO1MODE == SIOMODE_STD)
+SIO1A_CMD	.EQU	SIO1BASE + $01	
+SIO1A_DAT	.EQU	SIO1BASE + $00
+SIO1B_CMD	.EQU	SIO1BASE + $03
+SIO1B_DAT	.EQU	SIO1BASE + $02
+#ENDIF
+;
 #IF (SIO1MODE == SIOMODE_RC)
 SIO1A_CMD	.EQU	SIO1BASE + $00	
 SIO1A_DAT	.EQU	SIO1BASE + $01
@@ -90,13 +97,6 @@ SIO1B_CMD	.EQU	SIO1BASE + $07
 SIO1B_DAT	.EQU	SIO1BASE + $05
 #ENDIF
 ;
-#IF (SIO1MODE == SIOMODE_EZZ80)
-SIO1A_CMD	.EQU	SIO1BASE + $01	
-SIO1A_DAT	.EQU	SIO1BASE + $00
-SIO1B_CMD	.EQU	SIO1BASE + $03
-SIO1B_DAT	.EQU	SIO1BASE + $02
-#ENDIF
-;
 #ENDIF
 ;
 SIO_PREINIT:
@@ -158,44 +158,6 @@ SIO_PREINIT2:
 ;
 #ENDIF
 ;
-; FOR NOW, THIS IS SPECIFICALLY FOR A CTC TO DRIVE AN SIO
-; AT 1:1 USING CTC CHANNELS A & B.  IN OTHER WORDS, IT JUST
-; PASSES THE INCOMING TRIGGER OUT AT 1:1.
-;
-#IF (SIOCNT >= 1)
-  #IF (SIO0CTCC >= 0)
-	LD	A,%01010111		; CTCC CONTROL WORD VALUE
-		;  |||||||+-- 1=CONTROL WORD FLAG
-		;  ||||||+--- 1=SOFTWARE RESET
-		;  |||||+---- 1=TIME CONSTANT FOLLOWS
-		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
-		;  |||+------ 1=RISING EDGE TRIGGER
-		;  ||+------- 0=PRESCALER OF 16 (NOT USED)
-		;  |+-------- 1=COUNTER MODE
-		;  +--------- 0=NO INTERRUPTS
-	OUT	(CTCA + SIO0CTCC),A	; SETUP CTCC
-	LD	A,1			; CTC TIMER CONSTANT = 1
-	OUT	(CTCA + SIO0CTCC),A	; SETUP CTC TIMER CONSTANT
-  #ENDIF
-#ENDIF
-;
-#IF (SIOCNT >= 2)
-  #IF (SIO1CTCC >= 0)
-	LD	A,%01010111		; CTCC CONTROL WORD VALUE
-		;  |||||||+-- 1=CONTROL WORD FLAG
-		;  ||||||+--- 1=SOFTWARE RESET
-		;  |||||+---- 1=TIME CONSTANT FOLLOWS
-		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
-		;  |||+------ 1=RISING EDGE TRIGGER
-		;  ||+------- 0=PRESCALER OF 16 (NOT USED)
-		;  |+-------- 1=COUNTER MODE
-		;  +--------- 0=NO INTERRUPTS
-	OUT	(CTCA + SIO1CTCC),A	; SETUP CTCC
-	LD	A,1			; CTC TIMER CONSTANT = 1
-	OUT	(CTCA + SIO1CTCC),A	; SETUP CTC TIMER CONSTANT
-  #ENDIF
-#ENDIF
-;
 SIO_PREINIT3:
 	XOR	A			; SIGNAL SUCCESS
 	RET				; AND RETURN
@@ -538,72 +500,195 @@ SIO_INITDEV1:
 	CALL	PRTHEXWORD
 #ENDIF
 ;
-	LD	A,E			; GET CONFIG LSB
-	AND	$E0			; CHECK FOR DTR, XON, PARITY=MARK/SPACE
-	JR	NZ,SIO_INITFAIL		; IF ANY BIT SET, FAIL, NOT SUPPORTED
+	PUSH	DE			; SAVE TARGET CONFIG
+;
+	; WE WANT TO DETERMINE A DIVISOR FOR THE SIO CLOCK
+	; THAT RESULTS IN THE DESIRED BAUD RATE.
+	; BAUD RATE = SIO CLK / DIVISOR, OR TO SOLVE FOR DIVISOR
+	; DIVISOR = SIO CLK / BAUDRATE.
+	; TAKE ADVANTAGE OF ENCODED BAUD RATES ALWAYS BEING A FACTOR OF 75.
+	; SO, WE CAN USE (SIO OSC / 75) / (BAUDRATE / 75)
+;
+	; GET SERIAL CLOCK VALUE AND DIVIDE IT BY 75
+	PUSH	IY			; GET CONFIG TABLE ENTRY PTR
+	POP	HL			; MOVE TO HL
+	LD	A,9			; OFFSET TO CLK VALUE
+	CALL	ADDHLA			; HL IS NOW PTR TO 32 BIT CLK
+	CALL	LD32			; LOAD DE:HL W/ RAW CLK VAL
+	LD	C,75			; DIVIDE BY 75 LIKE BAUD RATE
+	CALL	DIV32X8			; HL NOW HAS (CLK / 75)
+;
+  #IF (SIODEBUG)
+	PRTS(" CLK75=$")
+	CALL	PRTHEX32
+  #ENDIF
+;
+	; SCALE DOWN THE 32 BIT VALUE TO FIT IN 16 BITS KEEPING
+	; TRACK OF THE NUMBER OF BITS SHIFTED OUT IN B
+	LD	B,0
+SIO_INITDEV1A:
+	LD	A,D
+	OR	E
+	JR	Z,SIO_INITDEV1B
+	SRL	D
+	RR	E
+	RR	H
+	RR	L
+	INC	B
+	JR	SIO_INITDEV1A
+SIO_INITDEV1B:
+;
+  #IF (SIODEBUG)
+	PRTS(" CLK=$")
+	CALL	PRTHEX32
+  #ENDIF
 ;
+	POP	DE			; RECOVER INCOMING TARGET CFG
+	PUSH	DE			; RESAVE IT
+	PUSH	HL			; SAVE CLK VALUE
+	PUSH	BC			; SAVE BITS SHIFTED
+
+	; NOW DECODE THE BAUDRATE, BUT WE USE A CONSTANT OF 1 INSTEAD
+	; OF THE NORMAL 75.  THIS PRODUCES (BAUDRATE / 75).
 	LD	A,D			; GET CONFIG MSB
 	AND	$1F			; ISOLATE ENCODED BAUD RATE
+	LD	L,A			; PUT IN L
+	LD	H,0			; H IS ALWAYS ZERO
+	LD	DE,1			; USE 1 FOR ENCODING CONSTANT
+	CALL	DECODE			; DE:HL := BAUD RATE, ERRORS IGNORED
+;
+  #IF (SIODEBUG)
+	PRTS(" BAUD75=$")
+	CALL	PRTHEX32
+  #ENDIF
+;	
+	; SCALE DOWN CLK BY SAME AMOUNT AS BAUD RATE
+	POP	BC			; RESTORE BITS TO SHIFT
+	LD	A,B
+	OR	A
+	JR	Z,SIO_INITDEV1D
+SIO_INITDEV1C:
+	SRL	D
+	RR	E
+	RR	H
+	RR	L
+	DJNZ	SIO_INITDEV1C
+SIO_INITDEV1D:
+;
+  #IF (SIODEBUG)
+	PRTS(" BAUD=$")
+	CALL	PRTHEX32
+  #ENDIF
+;	
+	POP	DE			; RECOVER CLOCK
+	EX	DE,HL			; SWAP CLOCK & BAUD FOR DIV
+	; *** HANDLE DIVIDE BY ZERO??? ***
+	CALL	DIV16			; BC := HL/DE == TARGET DIVISOR
 ;
-#IF (SIODEBUG)
-	PRTS(" ENC=$")
+  #IF (SIODEBUG)
+	PRTS(" DIV=$")
+	CALL	PRTHEXWORD
+  #ENDIF
+;
+	; NOW THAT WE HAVE THE TARGET BAUD RATE DIVISOR, WE WILL
+	; ATTEMPT TO IMPLEMENT IT.  THE SIO ITSELF CAN APPLY
+	; A DIVISOR OF 1, 16, 32, OR 64.  IF A CTC CHANNEL IS
+	; CONFIGURED FOR THIS SERIAL PORT, THEN WE CAN ADDITIONALLY
+	; APPLY A SCALER OF 1-256.
+;
+	; WE START BY DETERMINING THE MAXIMUM POSSIBLE SIO
+	; SCALING.
+;
+	; WARNING: IF THE INCOMING SIO CLOCK IS THE SAME AS THE 
+	; CPU CLOCK AND WE USE THE 1:1 DIVISOR, THE SIO WILL NOT
+	; WORK WELL.
+;
+	PUSH	BC			; MOVE WORKING DIVISOR VALUE
+	POP	HL			; ... TO HL
+	LD	A,L			; LOAD LSB OF DIVISOR
+	LD	BC,$0004		; SHIFT 0 BITS / SIO WR4 DIV 1
+	LD	A,L			; LOAD LSB OF DIVISOR
+	AND	%00001111		; DIV 16 POSSIBLE?
+	JR	NZ,SIO_INITDEV2		; NOPE, DONE TRYING
+	LD	BC,$0444		; SHIFT 4 BITS / SIO WR4 DIV 16
+	LD	A,L			; LOAD LSB OF DIVISOR
+	AND	%00011111		; DIV 32 POSSIBLE?
+	JR	NZ,SIO_INITDEV2		; NOPE, DONE TRYING
+	LD	BC,$0584		; SHIFT 5 BITS / SIO WR4 DIV 32
+	LD	A,L			; LOAD LSB OF DIVISOR
+	AND	%00111111		; DIV 32 POSSIBLE?
+	JR	NZ,SIO_INITDEV2		; NOPE, DONE TRYING
+	LD	BC,$06C4		; SHIFT 6 BITS / SIO WR4 DIV 64
+;
+	; NOW APPLY THE SIO DIVISOR TO THE WORKING DIVISOR
+	; AND SAVE THE RESULTANT SIO REGISTER VALUE TO APPLY LATER.
+SIO_INITDEV2:
+	; SHIFT BITS
+	XOR	A			; ZERO ACCUM
+	OR	B			; ZERO BITS TO SHIFT?
+	JR	Z,SIO_INITDEV4		; BYPASS SHIFTING IF SO
+SIO_INITDEV3:
+	RR	H			; SHIFT HL RIGHT BY
+	RR	L			; ONE BIT
+	DJNZ	SIO_INITDEV3		; UNTIL ALL BITS DONE
+SIO_INITDEV4:
+	LD	B,C			; MOVE SIO WR4 VALUE TO B
+;
+	POP	DE			; RESTORE DE = SERIAL CONFIG
+;
+  #IF (SIODEBUG)
+	PUSH	BC
+	PUSH	HL
+	POP	BC
+	PRTS(" CTCDIV=$")
+	CALL	PRTHEXWORD
+	POP	BC
+  #ENDIF
+;
+#IF (CTCENABLE)
+	LD	A,(IY+13)		; GET CTC CHANNEL
+	INC	A			; $FF -> 0
+	JR	Z,SIO_NOCTC		; NO CTC CHANNEL, BYPASS
+;
+	; HL HAS THE DIVISOR THAT WE WANT TO PROGRAM INTO THE
+	; DESIGNATED CTC CHANNEL.  HOWEVER, THE CTC REGISTER IS ONE
+	; BYTE.  A VALUE OF 0 MEANS 256.  SO WE NEED TO VALIDATE
+	; THAT HL IS BETWEEN 1 AND 256.
+	DEC	HL			; 1-256 -> 0-255
+	LD	A,H			; MSB NOW MUST BE ZERO
+	OR	A			; SET FLAGS
+	JR	NZ,SIO_INITFAIL		; IF ANY BIT SET, FAIL
+	INC	HL			; RESTORE HL
+;
+	; ALL GOOD.  PROGRAM THE CTC CHANNEL
+	LD	A,(IY+13)		; GET CTC CHANNEL
+	ADD	A,CTCA			; ADD TO CTC BASE PORT ADR
+  #IF (SIODEBUG)
+	PRTS(" CTC=$")
 	CALL	PRTHEXBYTE
+  #ENDIF
+	LD	C,A			; AND PUT IN C FOR I/O
+	LD	A,%01010111		; CTCC CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
+		;  ||||||+--- 1=SOFTWARE RESET
+		;  |||||+---- 1=TIME CONSTANT FOLLOWS
+		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
+		;  |||+------ 1=RISING EDGE TRIGGER
+		;  ||+------- 0=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
+		;  +--------- 0=NO INTERRUPTS
+	OUT	(C),A			; PREP CTC CHANNEL
+	OUT	(C),L			; SET CTC TIMER CONSTANT
+	JR	SIO_INITBROK		; AND REJOIN MAIN SETUP
+;
 #ENDIF
 ;
-	PUSH	DE			; SAVE REQUESTED CONFIG
-	LD	L,(IY+9)		; LOAD CLK FREQ
-	LD	H,(IY+10)		; ... INTO DE:HL
-	LD	E,(IY+11)		; ... "
-	LD	D,(IY+12)		; ... "
-	LD	C,75			; BAUD RATE ENCODING CONSTANT
-	CALL	ENCODE			; C = TEST BAUD RATE (ENCODED) = BAUDTST
-	POP	DE			; GET REQ CONFIG BACK, D = BAUDREQ
-;
-	; BIT 4 (DIV 3) OF BAUDREQ AND BAUDTST MUST MATCH!
-	LD	A,C			; A = BAUDTST
-	XOR	D			; XOR WITH BAUDREQ
-	BIT	4,A			; DO BIT 4 VALS MATCH?
-	JR	NZ,SIO_INITFAIL		; IF NOT, BAIL OUT
-;	
-	LD	A,C			; BAUDTST TO A
-	AND	$0F			; ISOLATE DIV 2 BAUD BITS
-	LD	C,A			; C = BAUDTST
-;	
-	LD	A,D			; MSB W/ BAUD RATE TO A
-	AND	$0F			; ISOLATE DIV 2 BAUD BITS
-	LD	L,A			; L = BAUDREQ
-;	
-;	PUSH	AF			; *DEBUG*
-;	CALL	NEWLINE                 ; *DEBUG*
-;	LD	A,L                     ; *DEBUG*
-;	CALL	PRTHEXBYTE              ; *DEBUG*
-;	LD	A,C                     ; *DEBUG*
-;	CALL	PRTHEXBYTE              ; *DEBUG*
-;	CALL	NEWLINE                 ; *DEBUG*
-;	POP	AF                      ; *DEBUG*
-;	
-	LD	A,C			; A = BAUDTST
-	LD	B,$04			; SIO R4 VAL FOR DIV 1
-	CP	L			; BAUDTST = BAUDREQ?
-	JR	Z,SIO_INITBROK		; IF MATCH, WE ARE DONE
-;	
-	SUB	4			; DIVIDE BY 16 (NOW DIV 16 TOT)
-	JR	C,SIO_INITFAIL		; FAIL IF UNDERFLOW
-	LD	B,$44			; SIO R4 VAL FOR DIV 16
-	CP	L			; BAUDTST = BAUDREQ?
-	JR	Z,SIO_INITBROK		; IF MATCH, WE ARE DONE
-;	
-	SUB	1			; DIVIDE BY 2 (NOW DIV 32 TOT)
-	JR	C,SIO_INITFAIL		; FAIL IF UNDERFLOW
-	LD	B,$84			; SIO R4 VAL FOR DIV 32
-	CP	L			; BAUDTST = BAUDREQ?
-	JR	Z,SIO_INITBROK		; IF MATCH, WE ARE DONE
-;	
-	SUB	1			; DIVIDE BY 2 (NOW DIV 64 TOT)
-	JR	C,SIO_INITFAIL		; FAIL IF UNDERFLOW
-	LD	B,$C4			; SIO R4 VAL FOR DIV 64
-	CP	L			; BAUDTST = BAUDREQ?
-	JR	Z,SIO_INITBROK		; IF MATCH, WE ARE DONE
+SIO_NOCTC:
+	; IF THERE IS NO CTC, THEN THE REMAINING DIVISOR
+	; NEEDS TO BE EXACTLY 1 OR WE HAVE A PROBLEM.
+	LD	A,L			; GET REMAINING DIVISOR
+	DEC	A			; 1 -> 0
+	JR	Z,SIO_INITBROK		; FAIL IF NOT 1
 ;
 SIO_INITFAIL:
 ;
@@ -665,6 +750,28 @@ SIO_INITBROK:
 ; FAILS.
 ;
 SIO_INITSAFE:
+;
+#IF (CTCENABLE)
+;
+	; CHECK IF A CTC CHANNEL IS CONFIGURED
+	LD	A,(IY+13)		; GET CTC CHANNEL
+	INC	A			; $FF -> 0
+	JR	Z,SIO_INITSAFE2		; NO CTC CHANNEL, BYPASS
+;
+	; IF A CTC CHANNEL IS CONFIGURED, PROGRAM IT FOR
+	; SIMPLE 1:1 SCALING.
+	LD	A,(IY+13)		; GET CTC CHANNEL
+	ADD	A,CTCA			; ADD TO CTC BASE PORT ADR
+	LD	C,A			; AND PUT IN C FOR I/O
+	LD	A,%01010111		; CTCC CONTROL WORD VALUE
+	OUT	(C),A			; PREP CTC CHANNEL
+	LD	A,1			; TIMER CONSTANT IS 1
+	OUT	(C),A			; SET CTC TIMER CONSTANT
+;
+#ENDIF
+;	
+SIO_INITSAFE2:
+	; SETUP DEFAULT VALUES FOR SIO REGISTERS
 	LD	HL,SIO_INITDEFS
 	LD	DE,SIO_INITVALS
 	LD	BC,SIO_INITLEN
@@ -764,7 +871,8 @@ SIO_INITLEN	.EQU	$ - SIO_INITVALS
 ;
 SIO_INITDEFS:
 	.DB	$00, $18		; WR0: CHANNEL RESET CMD
-	.DB	$04, $C4		; WR4: CLK BAUD PARITY STOP BIT
+	;.DB	$04, $C4		; WR4: CLK BAUD PARITY STOP BIT
+	.DB	$04, $44		; WR4: CLK BAUD PARITY STOP BIT
 	.DB	$01, SIO_WR1VAL		; WR1: INTERRUPT STYLE
 	.DB	$02, $00		; WR2: IM2 VEC OFFSET
 	.DB	$03, $E1		; WR3: 8 BIT RCV, CTS/DCD AUTO, RX ENABLE
@@ -984,8 +1092,9 @@ SIO0A_CFG:
 	.DB	SIO0A_DAT		; DATA PORT
 	.DW	SIO0ACFG		; LINE CONFIGURATION
 	.DW	SIO0A_RCVBUF		; POINTER TO RCV BUFFER STRUCT
-	.DW	(SIO0ACLK / SIO0ADIV) & $FFFF	; CLOCK FREQ AS
-	.DW	(SIO0ACLK / SIO0ADIV) >> 16	; ... DWORD VALUE
+	.DW	SIO0ACLK & $FFFF	; CLOCK FREQ AS
+	.DW	SIO0ACLK >> 16		; ... DWORD VALUE
+	.DB	SIO0ACTCC		; CTC CHANNEL
 ;
 SIO_CFGSIZ	.EQU	$ - SIO_CFG	; SIZE OF ONE CFG TABLE ENTRY
 ;
@@ -998,8 +1107,9 @@ SIO0B_CFG:
 	.DB	SIO0B_DAT		; DATA PORT
 	.DW	SIO0BCFG		; LINE CONFIGURATION
 	.DW	SIO0B_RCVBUF		; POINTER TO RCV BUFFER STRUCT
-	.DW	(SIO0BCLK / SIO0BDIV) & $FFFF	; CLOCK FREQ AS
-	.DW	(SIO0BCLK / SIO0BDIV) >> 16	; ... DWORD VALUE
+	.DW	SIO0BCLK & $FFFF	; CLOCK FREQ AS
+	.DW	SIO0BCLK >> 16		; ... DWORD VALUE
+	.DB	SIO0BCTCC		; CTC CHANNEL
 ;
 #IF (SIOCNT >= 2)
 ;
@@ -1012,8 +1122,9 @@ SIO1A_CFG:
 	.DB	SIO1A_DAT		; DATA PORT
 	.DW	SIO1ACFG		; LINE CONFIGURATION
 	.DW	SIO1A_RCVBUF		; POINTER TO RCV BUFFER STRUCT
-	.DW	(SIO1ACLK / SIO1ADIV) & $FFFF	; CLOCK FREQ AS
-	.DW	(SIO1ACLK / SIO1ADIV) >> 16	; ... DWORD VALUE
+	.DW	SIO1ACLK & $FFFF	; CLOCK FREQ AS
+	.DW	SIO1ACLK >> 16		; ... DWORD VALUE
+	.DB	SIO1ACTCC		; CTC CHANNEL
 ;
 	; SIO1 CHANNEL B
 SIO1B_CFG:
@@ -1024,8 +1135,9 @@ SIO1B_CFG:
 	.DB	SIO1B_DAT		; DATA PORT
 	.DW	SIO1BCFG		; LINE CONFIGURATION
 	.DW	SIO1B_RCVBUF		; POINTER TO RCV BUFFER STRUCT
-	.DW	(SIO1BCLK / SIO1BDIV) & $FFFF	; CLOCK FREQ AS
-	.DW	(SIO1BCLK / SIO1BDIV) >> 16	; ... DWORD VALUE
+	.DW	SIO1BCLK & $FFFF	; CLOCK FREQ AS
+	.DW	SIO1BCLK >> 16		; ... DWORD VALUE
+	.DB	SIO1BCTCC		; CTC CHANNEL
 ;
 #ENDIF
 ;
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index f0aa880d..af024490 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -119,10 +119,10 @@ DSRTCMODE_MFPIC	.EQU	2		; MF/PIC VARIANT
 ; SIO MODE SELECTIONS
 ;
 SIOMODE_NONE	.EQU	0
-SIOMODE_RC	.EQU	1		; RC2014 SIO MODULE (SPENCER OWEN)
-SIOMODE_SMB	.EQU	2		; RC2014 SIO MODULE (SCOTT BAKER)
-SIOMODE_ZP	.EQU	3		; ECB-ZILOG PERIPHERALS BOARD
-SIOMODE_EZZ80	.EQU	4		; EASY Z80 ON-BOARD SIO/0
+SIOMODE_STD	.EQU	1		; STD SIO REG CFG (EZZ80, KIO)
+SIOMODE_RC	.EQU	2		; RC2014 SIO MODULE (SPENCER OWEN)
+SIOMODE_SMB	.EQU	3		; RC2014 SIO MODULE (SCOTT BAKER)
+SIOMODE_ZP	.EQU	4		; ECB-ZILOG PERIPHERALS BOARD
 ;
 ; TYPE OF CONSOLE BELL TO USE
 ;
diff --git a/Source/Images/Common/COMP.COM b/Source/Images/Common/COMP.COM
new file mode 100644
index 00000000..d91f079f
Binary files /dev/null and b/Source/Images/Common/COMP.COM differ
diff --git a/Source/Images/Common/COMPARE.COM b/Source/Images/Common/COMPARE.COM
deleted file mode 100644
index 29fa41e6..00000000
Binary files a/Source/Images/Common/COMPARE.COM and /dev/null differ
diff --git a/Source/ver.inc b/Source/ver.inc
index 91ca16d7..26c4f45a 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,4 +2,4 @@
 #DEFINE	RMN	1
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.1-pre.2"
+#DEFINE BIOSVER	"3.1-pre.3"
diff --git a/Source/ver.lib b/Source/ver.lib
index bc39cfbf..a650a444 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	1
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.1-pre.2"
+	db	"3.1-pre.3"
 	endm