diff --git a/Doc/ChangeLog.txt b/Doc/ChangeLog.txt
index fd951ca1..4c990851 100644
--- a/Doc/ChangeLog.txt
+++ b/Doc/ChangeLog.txt
@@ -35,6 +35,7 @@ Version 3.1.1
 - D?N: Added support for RP5C01 RTC
 - L?N: Slightly enhanced ZCPRD&J w/ a couple bug fixes
 - L?N: UNZIPZ4 which handles most modern ZIP file compression algorithms
+- AJL: Preliminary support for MBC systems
 
 Version 3.1
 -----------
diff --git a/Source/HBIOS/Config/SBC_mbc.asm b/Source/HBIOS/Config/SBC_mbc.asm
new file mode 100644
index 00000000..1baa71aa
--- /dev/null
+++ b/Source/HBIOS/Config/SBC_mbc.asm
@@ -0,0 +1,33 @@
+;
+;==================================================================================================
+;   MBC CONFIGURATION
+;==================================================================================================
+;
+; THE COMPLETE SET OF DEFAULT CONFIGURATION SETTINGS FOR THIS PLATFORM ARE FOUND IN THE
+; CFG_<PLT>.ASM INCLUDED FILE WHICH IS FOUND IN THE PARENT DIRECTORY.  THIS FILE CONTAINS
+; COMMON CONFIGURATION SETTINGS THAT OVERRIDE THE DEFAULTS.  IT IS INTENDED THAT YOU MAKE
+; YOUR CUSTOMIZATIONS IN THIS FILE AND JUST INHERIT ALL OTHER SETTINGS FROM THE DEFAULTS.
+; EVEN BETTER, YOU CAN MAKE A COPY OF THIS FILE WITH A NAME LIKE <PLT>_XXX.ASM AND SPECIFY
+; YOUR FILE IN THE BUILD PROCESS.
+;
+; THE SETTINGS BELOW ARE THE SETTINGS THAT ARE MOST COMMONLY MODIFIED FOR THIS PLATFORM.
+; MANY OF THEM ARE EQUAL TO THE SETTINGS IN THE INCLUDED FILE, SO THEY DON'T REALLY DO
+; ANYTHING AS IS.  THEY ARE LISTED HERE TO MAKE IT EASY FOR YOU TO ADJUST THE MOST COMMON
+; SETTINGS.
+;
+; N.B., SINCE THE SETTINGS BELOW ARE REDEFINING VALUES ALREADY SET IN THE INCLUDED FILE,
+; TASM INSISTS THAT YOU USE THE .SET OPERATOR AND NOT THE .EQU OPERATOR BELOW. ATTEMPTING
+; TO REDEFINE A VALUE WITH .EQU BELOW WILL CAUSE TASM ERRORS!
+;
+; PLEASE REFER TO THE CUSTOM BUILD INSTRUCTIONS (README.TXT) IN THE SOURCE DIRECTORY (TWO
+; DIRECTORIES ABOVE THIS ONE).
+;
+#DEFINE PLATFORM_NAME "SBC"
+#DEFINE	BOOT_DEFAULT	"H"		; DEFAULT BOOT LOADER CMD ON <CR> OR AUTO BOOT
+;
+#include "cfg_sbc.asm"
+;
+INTMODE		.SET	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
+MEMMGR		.SET	MM_MBC		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
+;
+PPIDEENABLE	.SET	TRUE		; PPIDE: ENABLE PARALLEL PORT IDE DISK DRIVER (PPIDE.ASM)
diff --git a/Source/HBIOS/Makefile b/Source/HBIOS/Makefile
index e9e362a4..d98c460f 100644
--- a/Source/HBIOS/Makefile
+++ b/Source/HBIOS/Makefile
@@ -22,8 +22,9 @@ else
 	OBJECTS += RCZ80_std.rom RCZ80_std.com RCZ80_std.upd
 	OBJECTS += RCZ80_skz.rom RCZ80_skz.com RCZ80_skz.upd
 	OBJECTS += RCZ80_zrc.rom RCZ80_zrc.com RCZ80_zrc.upd
-	OBJECTS += SBC_simh.rom SBC_simh.com SBC_simh.upd
 	OBJECTS += SBC_std.rom SBC_std.com SBC_std.upd
+	OBJECTS += SBC_simh.rom SBC_simh.com SBC_simh.upd
+	OBJECTS += SBC_mbc.rom SBC_mbc.com SBC_mbc.upd
 	OBJECTS += SCZ180_126.rom SCZ180_126.com SCZ180_126.upd
 	OBJECTS += SCZ180_130.rom SCZ180_130.com SCZ180_130.upd
 	OBJECTS += SCZ180_131.rom SCZ180_131.com SCZ180_131.upd
diff --git a/Source/HBIOS/cfg_dyno.asm b/Source/HBIOS/cfg_dyno.asm
index 639a9e4b..35aad31c 100644
--- a/Source/HBIOS/cfg_dyno.asm
+++ b/Source/HBIOS/cfg_dyno.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_ezz80.asm b/Source/HBIOS/cfg_ezz80.asm
index 35aa287c..853e2f3f 100644
--- a/Source/HBIOS/cfg_ezz80.asm
+++ b/Source/HBIOS/cfg_ezz80.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	10000000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_115200_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_1	.EQU	$79		; Z2 MEM MGR BANK 1 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_2	.EQU	$7A		; Z2 MEM MGR BANK 2 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index 5119a04f..15f4c167 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -21,13 +21,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	8000000		; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_NONE		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_NONE		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 MPCL_RAM	.EQU	$78		; SBC MEM MGR RAM PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_mk4.asm b/Source/HBIOS/cfg_mk4.asm
index 55818ad2..11dee64f 100644
--- a/Source/HBIOS/cfg_mk4.asm
+++ b/Source/HBIOS/cfg_mk4.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 ;
diff --git a/Source/HBIOS/cfg_n8.asm b/Source/HBIOS/cfg_n8.asm
index c0162e17..85c47a57 100644
--- a/Source/HBIOS/cfg_n8.asm
+++ b/Source/HBIOS/cfg_n8.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_N8		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_N8		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMBIAS		.EQU	0		; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 RAMLOC		.EQU	0		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 ;
diff --git a/Source/HBIOS/cfg_rcz180.asm b/Source/HBIOS/cfg_rcz180.asm
index d61400ef..3bfccfcc 100644
--- a/Source/HBIOS/cfg_rcz180.asm
+++ b/Source/HBIOS/cfg_rcz180.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_115200_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_rcz280.asm b/Source/HBIOS/cfg_rcz280.asm
index bab1fb6f..9313f04b 100644
--- a/Source/HBIOS/cfg_rcz280.asm
+++ b/Source/HBIOS/cfg_rcz280.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	24000000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_115200_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_rcz80.asm b/Source/HBIOS/cfg_rcz80.asm
index 1ae6e7ff..d57b3e13 100644
--- a/Source/HBIOS/cfg_rcz80.asm
+++ b/Source/HBIOS/cfg_rcz80.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	7372800		; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	1		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	1		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_115200_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_1	.EQU	$79		; Z2 MEM MGR BANK 1 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_2	.EQU	$7A		; Z2 MEM MGR BANK 2 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index 2af4528c..6736e21f 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	8000000		; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_SBC		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_SBC		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 MPCL_RAM	.EQU	$78		; SBC MEM MGR RAM PAGE SELECT REG (WRITE ONLY)
 MPCL_ROM	.EQU	$7C		; SBC MEM MGR ROM PAGE SELECT REG (WRITE ONLY)
 ;
diff --git a/Source/HBIOS/cfg_scz180.asm b/Source/HBIOS/cfg_scz180.asm
index ec4aa57a..1ccc3846 100644
--- a/Source/HBIOS/cfg_scz180.asm
+++ b/Source/HBIOS/cfg_scz180.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_115200_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z180		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 RAMLOC		.EQU	19		; START OF RAM AS POWER OF 2 (2^N) IN PHYSICAL ADDRESS SPACE
 RAMBIAS		.EQU	(1 << (RAMLOC - 10))	; OFFSET OF START OF RAM IN PHYSICAL ADDRESS SPACE
 ;
diff --git a/Source/HBIOS/cfg_una.asm b/Source/HBIOS/cfg_una.asm
index b815f41b..8f589937 100644
--- a/Source/HBIOS/cfg_una.asm
+++ b/Source/HBIOS/cfg_una.asm
@@ -19,7 +19,7 @@ BIOS		.EQU	BIOS_UNA	; HARDWARE BIOS: BIOS_[WBW|UNA]
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	18432000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
diff --git a/Source/HBIOS/cfg_zeta.asm b/Source/HBIOS/cfg_zeta.asm
index fd8b94a3..127a24b0 100644
--- a/Source/HBIOS/cfg_zeta.asm
+++ b/Source/HBIOS/cfg_zeta.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	20000000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	0		; INTERRUPT MODE: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	0		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_SBC		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_SBC		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 MPCL_RAM	.EQU	$78		; SBC MEM MGR RAM PAGE SELECT REG (WRITE ONLY)
 MPCL_ROM	.EQU	$7C		; SBC MEM MGR ROM PAGE SELECT REG (WRITE ONLY)
 ;
diff --git a/Source/HBIOS/cfg_zeta2.asm b/Source/HBIOS/cfg_zeta2.asm
index 6271ca31..7bd79fc7 100644
--- a/Source/HBIOS/cfg_zeta2.asm
+++ b/Source/HBIOS/cfg_zeta2.asm
@@ -24,13 +24,13 @@ TICKFREQ	.EQU	50		; DESIRED PERIODIC TIMER INTERRUPT FREQUENCY (HZ)
 BOOT_TIMEOUT	.EQU	-1		; AUTO BOOT TIMEOUT IN SECONDS, -1 TO DISABLE, 0 FOR IMMEDIATE
 ;
 CPUOSC		.EQU	20000000	; CPU OSC FREQ IN MHZ
-INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
+INTMODE		.EQU	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2, 3=MODE 3 (Z280)
 DEFSERCFG	.EQU	SER_38400_8N1	; DEFAULT SERIAL LINE CONFIG (SEE STD.ASM)
 ;
 RAMSIZE		.EQU	512		; SIZE OF RAM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RAM_RESERVE	.EQU	0		; RESERVE FIRST N KB OF RAM (USUALLY 0)
 ROM_RESERVE	.EQU	0		; RESERVE FIRST N KB OR ROM (USUALLY 0)
-MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280]
+MEMMGR		.EQU	MM_Z2		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC]
 MPGSEL_0	.EQU	$78		; Z2 MEM MGR BANK 0 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_1	.EQU	$79		; Z2 MEM MGR BANK 1 PAGE SELECT REG (WRITE ONLY)
 MPGSEL_2	.EQU	$7A		; Z2 MEM MGR BANK 2 PAGE SELECT REG (WRITE ONLY)
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index e038cac3..81761114 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -116,8 +116,6 @@ MODCNT	.SET	MODCNT + 1
     #IF (INTMODE == 3)
 ; Z280 MODE 3 INTERRUPT HANDLING (INTA, C/T 0, & UART RCVR ENABLED)
 #DEFINE	HB_DI		DI
-;#DEFINE	HB_DI		.DB	$ED,$77,$7F
-;#DEFINE	HB_EI		EI
 #DEFINE	HB_EI		.DB	$ED,$7F,$0B
     #ELSE
 ; Z280 MODE 1/2 INTERRUPT HANDLING
@@ -486,6 +484,39 @@ HBX_ROM:
 	RET				; DONE
 #ENDIF
 ;
+#IF (MEMMGR == MM_MBC)
+;
+  #IF (INTMODE == 1)
+	LD	(HBX_MMA),A		; SAVE ACCUM
+	LD	A,I			; GET INT CTL REG
+	HB_DI				; DISABLE INTS
+	PUSH	AF			; SAVE INT CTL REG
+	LD	A,(HBX_MMA)		; RESTORE ACCUM
+  #ENDIF
+;
+        OR      A                       ; SET FLAGS
+        JP      P,HBX_ROM               ; BIT 7 INDICATES RAM
+        OUT     (MPCL_ROM),A            ; ENSURE ROM PAGE OUT OF MEMORY BEFORE SWITCH
+        OUT     (MPCL_RAM),A            ; SET RAM PAGE SELECTOR
+	JR	HBX_RAMX
+HBX_ROM:
+        OUT     (MPCL_RAM),A            ; ENSURE RAM PAGE OUT OF MEMORY BEFORE SWITCH
+        OUT     (MPCL_ROM),A            ; SET ROM PAGE SELECTOR
+
+HBX_RAMX:
+;
+  #IF (INTMODE == 1)
+	POP	AF			; RESTORE INT CTL REG
+	JP	PO,$+4			; WERE INTS DISABLED AT ENTRY?
+	EI				; *** DO NOT USE HB_EI HERE ***
+	LD	A,(HBX_MMA)		; RESTORE INCOMING ACCUM
+  #ENDIF
+;	
+	RET
+;
+HBX_MMA	.DB	0			; TEMPORARY STORAGE FOR REG A
+#ENDIF
+;
 ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
 ; Copy Data - Possibly between banks.  This resembles CP/M 3, but
 ;  usage of the HL and DE registers is reversed.
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index c8e09bf9..467d5d9f 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -84,6 +84,7 @@ MM_N8		.EQU	3		; Z180 CUSTOMIZED FOR N8 MEMORY EXTENSIONS
 MM_Z180		.EQU	4		; Z180 NATIVE MEMORY MANAGER
 MM_Z280		.EQU	5		; Z280 NATIVE MEMORY MANAGER
 MM_ZRC		.EQU	6		; ZRC BANK SWITCHING
+MM_MBC		.EQU	7		; MBC MEMORY MANAGER
 ;
 ; BOOT STYLE
 ;
diff --git a/Source/HBIOS/tms.asm b/Source/HBIOS/tms.asm
index dcacd838..09345ed4 100644
--- a/Source/HBIOS/tms.asm
+++ b/Source/HBIOS/tms.asm
@@ -381,8 +381,8 @@ TMS_SET:
 ;
 ;----------------------------------------------------------------------
 ; SET TMS9918 READ/WRITE ADDRESS
-;   TMS_WR SETS TMS9918 TO BEGIN WRITING TO ADDRESS SPECIFIED IN HL
-;   TMS_RD SETS TMS9918 TO BEGIN READING TO ADDRESS SPECIFIED IN HL
+;   TMS_WR SETS TMS9918 TO BEGIN WRITING AT VDU ADDRESS SPECIFIED IN HL
+;   TMS_RD SETS TMS9918 TO BEGIN READING AT VDU ADDRESS SPECIFIED IN HL
 ;----------------------------------------------------------------------
 ;
 TMS_WR:
@@ -390,8 +390,10 @@ TMS_WR:
         ; CLEAR R#14 FOR V9958
         XOR     A
         OUT     (TMS_CMDREG), A
+	TMS_IODELAY
         LD      A, $80 | 14
         OUT     (TMS_CMDREG), A
+	TMS_IODELAY
 #ENDIF
 
 	PUSH	HL
diff --git a/Source/ver.inc b/Source/ver.inc
index a7c448fd..7094aff8 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.82"
+#DEFINE BIOSVER	"3.1.1-pre.83"
diff --git a/Source/ver.lib b/Source/ver.lib
index dc13c2c4..245126b1 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.82"
+	db	"3.1.1-pre.83"
 	endm