diff --git a/Source/CBIOS/cbios.asm b/Source/CBIOS/cbios.asm
index fd9cbd4e..9f30a48a 100644
--- a/Source/CBIOS/cbios.asm
+++ b/Source/CBIOS/cbios.asm
@@ -3427,7 +3427,7 @@ DEV12	.DB	"SYQ$"
 DEV13	.DB	"CHUSB$"
 DEV14	.DB	"CHSD$"
 DEV15	.DB	"USB$"
-DEV16	.DB	"S100SD$"
+DEV16	.DB	"ESPSD$"
 DEV17	.EQU	DEVUNK
 ;
 #ENDIF
diff --git a/Source/Doc/Catalog.md b/Source/Doc/Catalog.md
index c8ea1a2b..6941c1eb 100644
--- a/Source/Doc/Catalog.md
+++ b/Source/Doc/Catalog.md
@@ -1238,6 +1238,7 @@ The following files are found in
 | `DRTCPM.OBJ`   | Startup Object File (???) |
 | `EXEC.H`       | Language include file (see manual) |
 | `FLOAT.H`      | Language include file (see manual) |
+| `HELLO.C`      | Sample C source file |
 | `HITECH.H`     | Language include file (see manual) |
 | `LIBC.LIB`     | Standard C Runtime Library |
 | `LIBF.LIB`     | Floating Point Library |
diff --git a/Source/HBIOS/Config/FZ80_std.asm b/Source/HBIOS/Config/FZ80_std.asm
index 1b80d5e2..9523b761 100644
--- a/Source/HBIOS/Config/FZ80_std.asm
+++ b/Source/HBIOS/Config/FZ80_std.asm
@@ -57,3 +57,4 @@ LPTENABLE	.SET	TRUE		; LPT: ENABLE CENTRONICS PRINTER DRIVER (LPT.ASM)
 ;
 ESPSDENABLE	.SET	TRUE		; ESPSD: ENABLE S100 ESP32 SD DISK DRIVER (ESPSD.ASM)
 ESPSDCNT	.SET	1		; ESPSD: NUMBER OF BOARDS TO DETECT (1-2), 1-2 DEVICES PER BOARD
+ESPSD0DUAL	.SET	TRUE		; ESPSD 0: DUAL INTERFACE BOARD (DUAL SD)
diff --git a/Source/HBIOS/Config/S100_std.asm b/Source/HBIOS/Config/S100_std.asm
index 83d7756d..9148156b 100644
--- a/Source/HBIOS/Config/S100_std.asm
+++ b/Source/HBIOS/Config/S100_std.asm
@@ -74,4 +74,4 @@ SDCNT		.SET	1		; SD: NUMBER OF SD CARD DEVICES (1-2), FOR DSD/SC/MT ONLY
 ;
 ESPSDENABLE	.SET	TRUE		; ESPSD: ENABLE S100 ESP32 SD DISK DRIVER (ESPSD.ASM)
 ESPSDCNT	.SET	1		; ESPSD: NUMBER OF BOARDS TO DETECT (1-2), 1-2 DEVICES PER BOARD
-
+ESPSD0DUAL	.SET	TRUE		; ESPSD 0: DUAL INTERFACE BOARD (DUAL SD)
diff --git a/Source/HBIOS/espsd.asm b/Source/HBIOS/espsd.asm
index b43da1a6..e99ef950 100644
--- a/Source/HBIOS/espsd.asm
+++ b/Source/HBIOS/espsd.asm
@@ -12,8 +12,7 @@
 ;
 ;
 ; TODO:
-; - ADD TIMEOUT TO DETECTION!!!
-; - ADD CARD DETECT FUNCTIONALITY
+; - AVOID RESELECTING PRI/SEC ON EVERY I/O CALL
 ;
 ; NOTES:
 ;
@@ -22,7 +21,6 @@
 ; COMMAND/RESPONSE PROTOCOL.  THE DUAL SD BOARD SUPPORTS TWO SD CARD
 ; DEVICES.  SEPARATE INIT AND SELECT COMMANDS ARE PROVIDED TO HANDLE
 ; THIS AS NEEDED.  THE 2CF+1SD SUPPORTS ONLY A SINGLE SD CARD DEVICE.
-; ONLY THE INIT/SELECT COMMANDS WITH A "0" SUFFIX CAN BE USED.
 ;
 ; TWO SEQUENTIAL I/O ADDRESSES ARE IMPLEMENTED.  THE FIRST IS
 ; FOR STATUS AND THE SECOND IS FOR COMMAND & DATA EXCHANGE.
@@ -53,35 +51,30 @@
 ;	XIN:	UNUSED???
 ;	XOUT:	ACTIVATE WRITE TO ESP32
 ;
-ESPSD_IO_STATUS	.EQU	0	; OFFSET OF STATUS PORT FROM BASE I/O ADDRESS
+ESPSD_IO_STATUS		.EQU	0	; OFFSET OF STATUS PORT FROM BASE I/O ADDRESS
 ESPSD_IO_DATA		.EQU	1	; OFFSET OF DATA PORT FROM BASE I/O ADDRESS
 ;
-ESPSD_CMD_INIT0	.EQU	$80	; Initialize primary SD Card
-ESPSD_CMD_INIT1	.EQU	$81	; INITIALIZE SECONDARY SD CARD
+ESPSD_CMD_INIT0		.EQU	$80	; Initialize primary SD Card
+ESPSD_CMD_INIT1		.EQU	$81	; INITIALIZE SECONDARY SD CARD
 ESPSD_CMD_SEL0		.EQU	$82	; (RE)SELECT PRIMARY SD CARD
 ESPSD_CMD_SEL1		.EQU	$83	; (RE)SELECT SECONDARY SD CARD
 ESPSD_CMD_SETLBA	.EQU	$84	; SET LBA FOR SUBSEQUENT I/O
 ESPSD_CMD_READ		.EQU	$85	; READ SECTOR FROM SELECTED SD CARD AT CURRENT LBA
-ESPSD_CMD_WRITE	.EQU	$86	; WRITE SECTOR TO SELECTED SD CARD AT CURRENT LBA
+ESPSD_CMD_WRITE		.EQU	$86	; WRITE SECTOR TO SELECTED SD CARD AT CURRENT LBA
 ESPSD_CMD_FORMAT	.EQU	$87	; FORMAT SECTOR ON SELECTED SD CARD AT CURRENT LBA
-ESPSD_CMD_RESET	.EQU	$88	; RESET ESP32 MODULE
+ESPSD_CMD_RESET		.EQU	$88	; RESET ESP32 MODULE
 ;
 ; ESPSD DEVICE STATUS CODES
 ;
 ESPSD_STOK		.EQU	0
-ESPSD_STINVUNIT	.EQU	-1
-ESPSD_STNOMEDIA	.EQU	-2
-ESPSD_STCMDERR		.EQU	-3
-ESPSD_STIOERR		.EQU	-4
-ESPSD_STRDYTO		.EQU	-5
-ESPSD_STDRQTO		.EQU	-6
-ESPSD_STBSYTO		.EQU	-7
-ESPSD_STNOTSUP		.EQU	-8
-ESPSD_STNOTRDY		.EQU	-9
+ESPSD_STNOMEDIA		.EQU	-1
+ESPSD_STIOERR		.EQU	-2
+ESPSD_STTO		.EQU	-3
+ESPSD_STNOTRDY		.EQU	-4
 ;
 ; IDE DEVICE CONFIGURATION
 ;
-ESPSD_CFGSIZ	.EQU	12		; SIZE OF CFG TBL ENTRIES
+ESPSD_CFGSIZ		.EQU	12		; SIZE OF CFG TBL ENTRIES
 ;
 ; PER DEVICE DATA OFFSETS
 ;
@@ -414,6 +407,18 @@ ESPSD_DETECT:
 ; INITIALIZE DEVICE
 ;
 ESPSD_INITDEV:
+	; CHECK CARD DETECT
+	LD	A,(IY+ESPSD_ROLE)	; GET ROLE
+	LD	B,%00000010		; MASK FOR PRIMARY
+	OR	A			; TEST ROLE
+	JR	Z,ESPSD_INITDEV1	; IF PRIMARY, JUMP AHEAD
+	LD	B,%00000100		; MASK FOR SECONDARY
+ESPSD_INITDEV1:
+	LD	C,(IY+ESPSD_IOBASE)	; STATUS PORT
+	IN	A,(C)			; GET STATUS
+	AND	B			; APPLY MASK
+	JP	Z,ESPSD_NOMEDIA		; IF NO CARD, HANDLE AS NO MEDIA
+;
 	CALL	ESPSD_INITCARD		; PERFORM DEVICE INIT
 	JP	NZ,ESPSD_NOMEDIA	; CONVERT TO NO MEDIA ERROR
 ;
@@ -638,7 +643,7 @@ ESPSD_PUTBYTE1:
 	JR	Z,ESPSD_PUTBYTE2
 	;JR	ESPSD_PUTBYTE1		; *DEBUG*
 	DJNZ	ESPSD_PUTBYTE1
-	LD	A,ESPSD_STBSYTO
+	LD	A,ESPSD_STTO
 	OR	A
 	RET
 ESPSD_PUTBYTE2:
@@ -657,7 +662,7 @@ ESPSD_PUTBYTE2:
 ;
 ESPSD_PUTBYTE_SLOW:
 	PUSH	HL
-	LD	HL,$1000		; *TODO* TUNE THIS VALUE!!!
+	LD	HL,50 * CPUMHZ		; CPU SPEED SCALED TIMEOUT
 ESPSD_PUTBYTE_SLOW1:
 	PUSH	HL
 	CALL	ESPSD_PUTBYTE
@@ -667,7 +672,7 @@ ESPSD_PUTBYTE_SLOW1:
 	LD	A,H
 	OR	L
 	JR	NZ,ESPSD_PUTBYTE_SLOW1
-	LD	A,ESPSD_STBSYTO
+	LD	A,ESPSD_STTO
 ESPSD_PUTBYTE_SLOW_Z:
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXWORDHL		; *DEBUG*
@@ -689,7 +694,7 @@ ESPSD_GETBYTE1:
 	BIT	7,A
 	JR	NZ,ESPSD_GETBYTE2
 	DJNZ	ESPSD_GETBYTE1
-	LD	A,ESPSD_STBSYTO
+	LD	A,ESPSD_STTO
 	OR	A
 	RET
 ESPSD_GETBYTE2:
@@ -708,7 +713,7 @@ ESPSD_GETBYTE2:
 ;
 ESPSD_GETBYTE_SLOW:
 	PUSH	HL
-	LD	HL,$1000		; *TODO* TUNE THIS VALUE???
+	LD	HL,50 * CPUMHZ		; CPU SPEED SCALED TIMEOUT
 ESPSD_GETBYTE_SLOW1:
 	PUSH	HL
 	CALL	ESPSD_GETBYTE
@@ -718,7 +723,7 @@ ESPSD_GETBYTE_SLOW1:
 	LD	A,H
 	OR	L
 	JR	NZ,ESPSD_GETBYTE_SLOW1
-	LD	A,ESPSD_STBSYTO
+	LD	A,ESPSD_STTO
 ESPSD_GETBYTE_SLOW_Z:
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXWORDHL		; *DEBUG*
@@ -732,36 +737,16 @@ ESPSD_GETBYTE_SLOW_Z:
 ;
 ; ERROR HANDLERS
 ;
-ESPSD_INVUNIT:
-	LD	A,ESPSD_STINVUNIT
-	JR	ESPSD_ERR2		; SPECIAL CASE FOR INVALID UNIT
-;
 ESPSD_NOMEDIA:
 	LD	A,ESPSD_STNOMEDIA
 	JR	ESPSD_ERR
 ;
-ESPSD_CMDERR:
-	LD	A,ESPSD_STCMDERR
-	JR	ESPSD_ERR
-;
 ESPSD_IOERR:
 	LD	A,ESPSD_STIOERR
 	JR	ESPSD_ERR
 ;
-ESPSD_RDYTO:
-	LD	A,ESPSD_STRDYTO
-	JR	ESPSD_ERR
-;
-ESPSD_DRQTO:
-	LD	A,ESPSD_STDRQTO
-	JR	ESPSD_ERR
-;
-ESPSD_BSYTO:
-	LD	A,ESPSD_STBSYTO
-	JR	ESPSD_ERR
-;
-ESPSD_NOTSUP:
-	LD	A,ESPSD_STNOTSUP
+ESPSD_TO:
+	LD	A,ESPSD_STTO
 	JR	ESPSD_ERR
 ;
 ESPSD_NOTRDY:
@@ -771,7 +756,6 @@ ESPSD_NOTRDY:
 ESPSD_ERR:
 	LD	(IY+ESPSD_STAT),A	; SAVE NEW STATUS
 ;
-ESPSD_ERR2:
 #IF (ESPSDTRACE >= 2)
 	CALL	ESPSD_PRTSTAT
 #ENDIF
@@ -791,8 +775,6 @@ ESPSD_PRTSTAT:
 	PUSH	DE
 	PUSH	HL
 	LD	A,(IY+ESPSD_STAT)
-	CP	ESPSD_STINVUNIT
-	JR	Z,ESPSD_PRTSTAT2		; INVALID UNIT IS SPECIAL CASE
 	CALL	ESPSD_PRTPREFIX		; PRINT UNIT PREFIX
 	JR	ESPSD_PRTSTAT3
 ESPSD_PRTSTAT2:
@@ -816,28 +798,13 @@ ESPSD_PRTSTATSTR:
 	LD	DE,ESPSD_STR_STOK
 	JR	Z,ESPSD_PRTSTATSTR1
 	INC	A
-	LD	DE,ESPSD_STR_STINVUNIT
-	JR	Z,ESPSD_PRTSTATSTR1
-	INC	A
 	LD	DE,ESPSD_STR_STNOMEDIA
 	JR	Z,ESPSD_PRTSTATSTR1
 	INC	A
-	LD	DE,ESPSD_STR_STCMDERR
-	JR	Z,ESPSD_PRTSTATSTR1
-	INC	A
 	LD	DE,ESPSD_STR_STIOERR
 	JR	Z,ESPSD_PRTSTATSTR1
 	INC	A
-	LD	DE,ESPSD_STR_STRDYTO
-	JR	Z,ESPSD_PRTSTATSTR1
-	INC	A
-	LD	DE,ESPSD_STR_STDRQTO
-	JR	Z,ESPSD_PRTSTATSTR1
-	INC	A
-	LD	DE,ESPSD_STR_STBSYTO
-	JR	Z,ESPSD_PRTSTATSTR1
-	INC	A
-	LD	DE,ESPSD_STR_STNOTSUP
+	LD	DE,ESPSD_STR_STTO
 	JR	Z,ESPSD_PRTSTATSTR1
 	INC	A
 	LD	DE,ESPSD_STR_STNOTRDY
@@ -869,16 +836,11 @@ ESPSD_PRTPREFIX1:
 ;=============================================================================
 ;
 ESPSD_STR_STOK		.TEXT	"OK$"
-ESPSD_STR_STINVUNIT	.TEXT	"INVALID UNIT$"
 ESPSD_STR_STNOMEDIA	.TEXT	"NO MEDIA$"
-ESPSD_STR_STCMDERR	.TEXT	"COMMAND ERROR$"
 ESPSD_STR_STIOERR	.TEXT	"IO ERROR$"
-ESPSD_STR_STRDYTO	.TEXT	"READY TIMEOUT$"
-ESPSD_STR_STDRQTO	.TEXT	"DRQ TIMEOUT$"
-ESPSD_STR_STBSYTO	.TEXT	"BUSY TIMEOUT$"
-ESPSD_STR_STNOTSUP	.TEXT	"NOT SUPPORTED$"
+ESPSD_STR_STTO		.TEXT	"TIMEOUT$"
 ESPSD_STR_STNOTRDY	.TEXT	"NOT READY$"
-ESPSD_STR_STUNK	.TEXT	"UNKNOWN ERROR$"
+ESPSD_STR_STUNK		.TEXT	"UNKNOWN ERROR$"
 ;
 ;=============================================================================
 ; DATA STORAGE
diff --git a/Source/ver.inc b/Source/ver.inc
index c44c4263..01ff111e 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	6
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.6.0-dev.17"
+#DEFINE BIOSVER	"3.6.0-dev.18"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index 6ab08361..de03258f 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	6
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.6.0-dev.17"
+	db	"3.6.0-dev.18"
 	endm