diff --git a/Source/HBIOS/cfg_ezz80.asm b/Source/HBIOS/cfg_ezz80.asm
index bef8fe9a..6914d777 100644
--- a/Source/HBIOS/cfg_ezz80.asm
+++ b/Source/HBIOS/cfg_ezz80.asm
@@ -119,6 +119,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index ebbc1b1a..cf909f77 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -149,6 +149,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ASCISWAP	.EQU	FALSE		; ASCI: SWAP CHANNELS
diff --git a/Source/HBIOS/cfg_mbc.asm b/Source/HBIOS/cfg_mbc.asm
index 0c5169c3..663d310a 100644
--- a/Source/HBIOS/cfg_mbc.asm
+++ b/Source/HBIOS/cfg_mbc.asm
@@ -112,6 +112,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	TRUE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_mk4.asm b/Source/HBIOS/cfg_mk4.asm
index 7c3633fd..ac49671d 100644
--- a/Source/HBIOS/cfg_mk4.asm
+++ b/Source/HBIOS/cfg_mk4.asm
@@ -118,6 +118,7 @@ UARTCAS		.EQU	TRUE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	TRUE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	TRUE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ASCISWAP	.EQU	FALSE		; ASCI: SWAP CHANNELS
diff --git a/Source/HBIOS/cfg_n8.asm b/Source/HBIOS/cfg_n8.asm
index e94d0250..f62e7c14 100644
--- a/Source/HBIOS/cfg_n8.asm
+++ b/Source/HBIOS/cfg_n8.asm
@@ -120,6 +120,7 @@ UARTCAS		.EQU	TRUE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	TRUE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	TRUE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ASCISWAP	.EQU	FALSE		; ASCI: SWAP CHANNELS
diff --git a/Source/HBIOS/cfg_rcz180.asm b/Source/HBIOS/cfg_rcz180.asm
index 08201106..5a7e91b7 100644
--- a/Source/HBIOS/cfg_rcz180.asm
+++ b/Source/HBIOS/cfg_rcz180.asm
@@ -121,6 +121,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	TRUE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ASCISWAP	.EQU	FALSE		; ASCI: SWAP CHANNELS
diff --git a/Source/HBIOS/cfg_rcz280.asm b/Source/HBIOS/cfg_rcz280.asm
index a05f2971..882dfb43 100644
--- a/Source/HBIOS/cfg_rcz280.asm
+++ b/Source/HBIOS/cfg_rcz280.asm
@@ -126,6 +126,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_rcz80.asm b/Source/HBIOS/cfg_rcz80.asm
index 31221bc9..5c2c5825 100644
--- a/Source/HBIOS/cfg_rcz80.asm
+++ b/Source/HBIOS/cfg_rcz80.asm
@@ -120,6 +120,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index dd683a31..830ab4fc 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -112,6 +112,7 @@ UARTCAS		.EQU	TRUE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	TRUE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	TRUE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_scz180.asm b/Source/HBIOS/cfg_scz180.asm
index 226ed9bc..265ea1e2 100644
--- a/Source/HBIOS/cfg_scz180.asm
+++ b/Source/HBIOS/cfg_scz180.asm
@@ -116,6 +116,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	TRUE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ASCISWAP	.EQU	FALSE		; ASCI: SWAP CHANNELS
diff --git a/Source/HBIOS/cfg_zeta.asm b/Source/HBIOS/cfg_zeta.asm
index fcf3aadd..8a2bb725 100644
--- a/Source/HBIOS/cfg_zeta.asm
+++ b/Source/HBIOS/cfg_zeta.asm
@@ -99,6 +99,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/cfg_zeta2.asm b/Source/HBIOS/cfg_zeta2.asm
index ab96ffec..30983347 100644
--- a/Source/HBIOS/cfg_zeta2.asm
+++ b/Source/HBIOS/cfg_zeta2.asm
@@ -110,6 +110,7 @@ UARTCAS		.EQU	FALSE		; UART: AUTO-DETECT ECB CASSETTE UART
 UARTMFP		.EQU	FALSE		; UART: AUTO-DETECT MF/PIC UART
 UART4		.EQU	FALSE		; UART: AUTO-DETECT 4UART UART
 UARTRC		.EQU	FALSE		; UART: AUTO-DETECT RC UART
+UARTDUAL	.EQU	FALSE		; UART: AUTO-DETECT DUAL UART
 ;
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
diff --git a/Source/HBIOS/uart.asm b/Source/HBIOS/uart.asm
index a24de3d0..4045a6e9 100644
--- a/Source/HBIOS/uart.asm
+++ b/Source/HBIOS/uart.asm
@@ -58,6 +58,7 @@ UARTCBASE		.EQU	$80
 UARTMBASE		.EQU	$48
 UART4BASE		.EQU	$C0
 UARTRBASE		.EQU	$A0
+UARTDBASE		.EQU	$80
 ;
 #IF (UARTINTS)
 ;
@@ -557,6 +558,16 @@ UART_INITDEV1A:
 	LD	A,(IY+5)		; GET CONFIG BYTE
 	AND	~$1F			; REMOVE ENCODED BAUD RATE BITS
 	OR	$03			; FORCE RTS & DTR
+;
+	; SOME NEWER UARTS USE MCR:3 TO ACTIVATE THE INTERRUPT LINE.
+	; ALTHOUGH OTHER UARTS USE MCR:3 TO CONTROL A GPIO LINE CALLED
+	; OUT2, NO ROMWBW HARDWARE USES THIS GPIO LINE.  SO, HERE, WE
+	; JUST SET MCR:3 TO ACTIVATE THE INTERRUPT LINE.  NOTE THAT
+	; EVEN IF WE ARE NOT USING INTERRUPTS FOR THIS UART, THE
+	; INTERRUPT LINE MUST STILL BE ACTIVATED SO THAT IT WILL
+	; PRESENT A DEASSERTED CONDITION TO THE CPU.  OTHERWISE, THE
+	; INTERRUPT LINE MAY BE LEFT FLOATING WHICH IS DEFINITELY BAD.
+	OR	$08			; ACTIVATE INT LINE
 ;
 	; THE MCR REGISTER AFE BIT WILL NORMALLY BE SET/RESET BY THE
 	; VALUE OF THE CONFIG BYTE.  HOWEVER, IF THE CHIP IS NOT AFC CAPABLE
@@ -1058,6 +1069,22 @@ UART_CFG_MFP:
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.DW	0				; SHOULD NEVER NEED INT HANDLER
 #ENDIF
+#IF (UARTDUAL)
+	; DUAL UART CHANNEL A
+	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
+	.DB	0				; UART TYPE
+	.DB	UARTDBASE			; IO PORT BASE (RBR, THR)
+	.DB	UARTDBASE + UART_LSR		; LINE STATUS PORT (LSR)
+	.DW	UARTCFG				; LINE CONFIGURATION
+	.DW	0				; SHOULD NEVER NEED INT HANDLER
+	; DUAL UART CHANNEL B
+	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
+	.DB	0				; UART TYPE
+	.DB	UARTDBASE+8			; IO PORT BASE (RBR, THR)
+	.DB	UARTDBASE+8 + UART_LSR		; LINE STATUS PORT (LSR)
+	.DW	UARTCFG				; LINE CONFIGURATION
+	.DW	0				; SHOULD NEVER NEED INT HANDLER
+#ENDIF
 ;
 UART_CNT	.EQU	($ - UART_CFG) / 8
 ;
diff --git a/Source/TastyBasic/src/Build.cmd b/Source/TastyBasic/src/Build.cmd
index aa526159..11a556be 100644
--- a/Source/TastyBasic/src/Build.cmd
+++ b/Source/TastyBasic/src/Build.cmd
@@ -7,7 +7,7 @@ set PATH=%TOOLS%\tasm32;%PATH%
 
 set TASMTABS=%TOOLS%\tasm32
 
-# git@github.com:dimitrit/tastybasic.git; commit a86d7e7; (HEAD -> master, tag: v0.3.0) 
+:: git@github.com:dimitrit/tastybasic.git; commit a86d7e7; (HEAD -> master, tag: v0.3.0) 
 set VER=v0.3.0
 
 tasm -80 -g3 -fFF -dROMWBW -d"VERSION \"%VER%\"" tastybasic.asm tastybasic.bin tastybasic.bin.lst
diff --git a/Source/ver.inc b/Source/ver.inc
index 6d15aae4..5a9f50a1 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,4 +2,4 @@
 #DEFINE	RMN	1
 #DEFINE	RUP	1
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.1.1-pre.136"
+#DEFINE BIOSVER	"3.1.1-pre.137"
diff --git a/Source/ver.lib b/Source/ver.lib
index f196db79..96a49209 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	1
 rup	equ	1
 rtp	equ	0
 biosver	macro
-	db	"3.1.1-pre.136"
+	db	"3.1.1-pre.137"
 	endm