diff --git a/Source/HBIOS/hdsk.asm b/Source/HBIOS/hdsk.asm
index 82ed8ac2..ce70779f 100644
--- a/Source/HBIOS/hdsk.asm
+++ b/Source/HBIOS/hdsk.asm
@@ -79,15 +79,15 @@ HDSK_CAP:
 	XOR	A			; SIGNAL SUCCESS
 	RET
 ;
-; GET GEOMETRY
-;   RETURN HL:DE=CYLINDERS, B=HEADS, C=SECTORS
-;
-HDSK_GEOM:
-	LD	DE,0			; CYLINDER COUNT MSW
-	LD	HL,520			; CYLINDER COUNT LSW
-	LD	B,16			; HEADS / CYLINDER
-	LD	C,16			; SECTORS / TRACK
-	XOR	A			; SIGNAL SUCCESS
+SD_GEOM:
+	; FOR LBA, WE SIMULATE CHS ACCESS USING 16 HEADS AND 16 SECTORS
+	; RETURN HS:CC -> DE:HL, SET HIGH BIT OF D TO INDICATE LBA CAPABLE
+	CALL	SD_CAP				; GET TOTAL BLOCKS IN DE:HL, BLOCK SIZE TO BC
+	LD	L,H				; DIVIDE BY 256 FOR # TRACKS
+	LD	H,E				; ... HIGH BYTE DISCARDED, RESULT IN HL
+	LD	D,$80 | 16			; HEADS / CYL = 16, SET LBA BIT
+	LD	E,16				; SECTORS / TRACK = 16
+	XOR	A				; SIGNAL SUCCESS
 	RET
 ;
 ;
diff --git a/Source/HBIOS/sd.asm b/Source/HBIOS/sd.asm
index 6cc1bcd2..38782356 100644
--- a/Source/HBIOS/sd.asm
+++ b/Source/HBIOS/sd.asm
@@ -6,7 +6,7 @@
 ; 1) TESTING
 ;    - TRY TO TEST GOIDLE, FIND CARD THAT REQUIRES 2 REQUESTS
 ;    - DUAL CARDS
-;    - CARD XC CARD TYPE DETECTION
+;    - TEST XC CARD TYPE DETECTION
 ;    - TRY TO GET INIT TO FAIL, REMOVE DELAYS AT START OF GOIDLE?
 ;
 ;------------------------------------------------------------------------------
@@ -454,14 +454,18 @@ SD_MEDIA:
 SD_CAP:
 	SD_DPTR(SD_CAPACITY)			; POINT HL TO CAPACITY OF CUR UNIT
 	CALL	LD32				; GET THE CURRENT CAPACITY DO DE:HL
+	LD	BC,512				; 512 BYTES PER BLOCK
 	XOR	A				; SIGNAL SUCCESS
 	RET					; AND DONE
 ;
 SD_GEOM:
-	LD	DE,0				; CYLINDER COUNT MSW
-	LD	HL,520				; CYLINDER COUNT LSW
-	LD	B,16				; HEADS / CYLINDER
-	LD	C,16				; SECTORS / TRACK
+	; FOR LBA, WE SIMULATE CHS ACCESS USING 16 HEADS AND 16 SECTORS
+	; RETURN HS:CC -> DE:HL, SET HIGH BIT OF D TO INDICATE LBA CAPABLE
+	CALL	SD_CAP				; GET TOTAL BLOCKS IN DE:HL, BLOCK SIZE TO BC
+	LD	L,H				; DIVIDE BY 256 FOR # TRACKS
+	LD	H,E				; ... HIGH BYTE DISCARDED, RESULT IN HL
+	LD	D,16 | $80			; HEADS / CYL = 16, SET LBA BIT
+	LD	E,16				; SECTORS / TRACK = 16
 	XOR	A				; SIGNAL SUCCESS
 	RET
 ;
@@ -1066,6 +1070,14 @@ SD_WAITRDY1:
 ;
 ; FINISH A TRANSACTION - PRESERVE AF
 ;
+; PER SPEC: AFTER THE LAST SPI BUS TRANSACTION, THE HOST IS REQUIRED, TO PROVIDE
+; 8 (EIGHT) CLOCK CYCLES FOR THE CARD TO COMPLETE THE OPERATION BEFORE SHUTTING
+; DOWN THE CLOCK. THROUGHOUT THIS 8 CLOCKS PERIOD THE STATE OF THE CS SIGNAL IS
+; IRRELEVANT. IT CAN BE ASSERTED OR DE-ASSERTED.
+;
+; NOTE THAT I HAVE FOUND AT LEAST ONE MMC CARD THAT FAILS UNLESS THE CS SIGNAL
+; REMAINS ACTIVE DURING THE 8 CLOCKS, SO THE CLOCKS ARE SENT BEFORE DESLECTING THE CARD.
+;
 SD_DONE:
 	PUSH	AF
 	LD	A,$FF