diff --git a/source/command/msxdos/sys.mac b/source/command/msxdos/sys.mac
index 4ef33d4d..eca152bc 100644
--- a/source/command/msxdos/sys.mac
+++ b/source/command/msxdos/sys.mac
@@ -1017,6 +1017,11 @@ zstr_slow:
 	;LD	E,RELEASE##+(RELEASE##/256)*16
 	ret
 
+@GPART:
+	;Needs CALL (can't use JP) due to how FUNC_WITH_IXIY manages stack
+	call	FUNC_WITH_IXIY
+	ret
+
 FUNC_WITH_IXIY:
 	EXX
 	pop	bc
@@ -1263,7 +1268,6 @@ _KBSDE:	LD	DE,BUFF1	; DE -> buffer containing FIB or string.
 @RALLOC:
 @DSPACE:
 @LOCK:
-@GPART:
 @Z80MODE:
 
 ;
diff --git a/source/command/msxdos/ver.mac b/source/command/msxdos/ver.mac
index eae52866..d71b1d7f 100644
--- a/source/command/msxdos/ver.mac
+++ b/source/command/msxdos/ver.mac
@@ -9,8 +9,8 @@
 ;
 ;
 VERSION	EQU	2
-RELEASE	EQU	1*256+1			; Version 2.11.
-CRYEAR	EQU	2019
+RELEASE	EQU	1*256+2			; Version 2.12.
+CRYEAR	EQU	2021
 ;
 GLOBAL	VERSION, RELEASE, CRYEAR
 ;
diff --git a/source/kernel/Makefile b/source/kernel/Makefile
index 692ecf7d..fe733988 100644
--- a/source/kernel/Makefile
+++ b/source/kernel/Makefile
@@ -4,7 +4,7 @@
 # See the "all" main rule for some handy aliases to generate specific ROMs
 # (e.g. you can run "make base" or "make ide").
 
-VERSION := 2.1.1-alpha2
+VERSION := 2.1.1-beta1
 
 export X80_COMMAND_LINE=-t -nb
 export M80_COMMAND_LINE=-8
@@ -31,7 +31,7 @@ endef
 ###  MAIN RULE  ###
 ###################
 
-all: base ide ide-emu ascii8 ascii16 mfrsd flashjacks
+all: base ide ide-emu ascii8 ascii16 mfrsd flashjacks ocm
 
 TOOLS := M80 L80 LIB80 objcopy sdcc mknexrom dd
 
@@ -216,6 +216,18 @@ drivers/Flashjacks/Nextor-$(VERSION).Flashjacks.ROM: \
 	$(call copy_to_bin,$@)
 
 
+### OCM (1-chip MSX, SX|2, and compatibles)
+
+ocm: drivers/OCM/Nextor-$(VERSION).OCM.ROM
+
+drivers/OCM/Nextor-$(VERSION).OCM.ROM: \
+	nextor_base.dat \
+	drivers/StandaloneASCII8/CHGBNK.BIN
+
+	mknexrom nextor_base.dat $@ /d:drivers/OCM/driver.dat /m:drivers/StandaloneASCII8/CHGBNK.BIN
+	$(call copy_to_bin,$@)
+
+
 ### Common rules
 
 256.bytes:
diff --git a/source/kernel/bank1/mapinit.mac b/source/kernel/bank1/mapinit.mac
index e5280e7c..477d77e1 100644
--- a/source/kernel/bank1/mapinit.mac
+++ b/source/kernel/bank1/mapinit.mac
@@ -687,6 +687,12 @@ MAPBIO::
 ;   For other values of D, the EXTBIO hook on the driver bank is called with D'=1.
 ;   This must return D'=1 if old hook must be called, D'=0 otherwise.
 
+		push de	;DE must always be preserved
+		call MAPBDO
+		pop de
+		ret
+
+MAPBDO:
 		exx
 		set	0,d
 		exx
diff --git a/source/kernel/condasm.inc b/source/kernel/condasm.inc
index 64273e35..df33540e 100644
--- a/source/kernel/condasm.inc
+++ b/source/kernel/condasm.inc
@@ -8,9 +8,9 @@ HYBRID	equ	-1		;DOS1/DOS2 hybrid system
 STURBO	equ	-1		;support super turbo mode (for MSXturboR)
 BUILTIN	equ	-1		;built-in system
 
-ALPHA	equ	2		;Level of Alpha release (0: no alpha)
+ALPHA	equ	0		;Level of Alpha release (0: no alpha)
 ALPHAL	equ	""		;Letter after the Alpha release number, or empty
-BETA	equ	0		;Level of Beta release (0: no beta)
+BETA	equ	1		;Level of Beta release (0: no beta)
 RC	equ	0		;Level of RC (0: no RC)
 RR  equ 0       ;Level of release (0: no release level)
 ;
diff --git a/source/kernel/drivers/OCM/driver.dat b/source/kernel/drivers/OCM/driver.dat
new file mode 100644
index 00000000..340965a9
Binary files /dev/null and b/source/kernel/drivers/OCM/driver.dat differ