diff --git a/docs/NoSlotClock/DallasSmartWatchUtilityDisassembly.txt b/docs/NoSlotClock/DallasSmartWatchUtilityDisassembly.txt
index 2488a9ab..02cccd89 100644
--- a/docs/NoSlotClock/DallasSmartWatchUtilityDisassembly.txt
+++ b/docs/NoSlotClock/DallasSmartWatchUtilityDisassembly.txt
@@ -1,7 +1,9 @@
-Dallas SmartWatch DS1216 (No-Slot-Clock) SmartWatch Utility (Version 1.1).
+Dallas SmartWatch DS1216 (No-Slot-Clock) SmartWatch Utility (Version 1.1) "SWU.SYSTEM".
 Copyright 1987 Matthew Lee Stier.
 Partial disassembly and comments by Nick Westgate (and CiderPress).
 
+Note: This code requires the clock to be in the internal C3 ROM space. (CD or CF ROM sockets.)
+
 2000-   A2 FF       LDX   #$FF     ;reset stack
 2002-   9A          TXS
 2003-   20 58 22    JSR   $2258
diff --git a/docs/NoSlotClock/GeosNoSlotClockDriverDisassembly.txt b/docs/NoSlotClock/GeosNoSlotClockDriverDisassembly.txt
index fd03c480..bd125ed2 100644
--- a/docs/NoSlotClock/GeosNoSlotClockDriverDisassembly.txt
+++ b/docs/NoSlotClock/GeosNoSlotClockDriverDisassembly.txt
@@ -1,7 +1,7 @@
-Dallas SmartWatch DS1216 (No-Slot-Clock) GEOS driver.
+No-Slot-Clock (Dallas SmartWatch DS1216) GEOS driver "NoSlot Clock".
 Partial disassembly and comments by Nick Westgate (and CiderPress).
 
-Note: This code requires the clock to be in the internal C8 ROM space.
+Note: This code requires the clock to be in the internal C8 ROM space. (CD or CF ROM sockets.)
 
 0800-   4C 15 08    JMP   $0815    ;read time
 0803-   4C B8 08    JMP   $08B8
diff --git a/docs/NoSlotClock/NoSlotClockDriverDisassembly.txt b/docs/NoSlotClock/NoSlotClockDriverDisassembly.txt
index e0cc4f15..552334a6 100644
--- a/docs/NoSlotClock/NoSlotClockDriverDisassembly.txt
+++ b/docs/NoSlotClock/NoSlotClockDriverDisassembly.txt
@@ -1,7 +1,9 @@
-No-Slot-Clock (Dallas SmartWatch DS1216) ProDOS Driver.
+No-Slot-Clock (Dallas SmartWatch DS1216) ProDOS Driver "NS.CLOCK.SYSTEM".
 Probably written by Craig Peterson in 1990.
 Partial disassembly and comments by Nick Westgate (and CiderPress).
 
+Note: This code checks for the clock in internal C3, C8 and external slot ROM spaces. (CD, CF or slot ROM sockets.)
+
 2000-   38          SEC            ;actually loads at $2000
 2001-   B0 03       BCS   $2006
 2003-   09 23
@@ -90,7 +92,7 @@ Partial disassembly and comments by Nick Westgate (and CiderPress).
 10CF-   8C F8 13    STY   $13F8
 10D2-   8D 66 14    STA   $1466    ;(STA $CFFF)
 10D5-   8C 65 14    STY   $1465
-10D8-   A9 00       LDA   #$00     ;slot (3, 1..7)
+10D8-   A9 00       LDA   #$00     ;slot (3, 1..7, C8 internal)
 10DA-   8D 9C 11    STA   $119C    ;count?
 10DD-   A9 03       LDA   #$03
 10DF-   09 C0       ORA   #$C0
@@ -130,8 +132,7 @@ Partial disassembly and comments by Nick Westgate (and CiderPress).
 112B-   AD 9C 11    LDA   $119C
 112E-   C9 08       CMP   #$08
 1130-   90 AD       BCC   $10DF
-1132-   D0 1D       BNE   $1151    ;stop after slots 3, 1..7
-
+1132-   D0 1D       BNE   $1151    ;loop for slots 3, 1..7
 1134-   A9 C0       LDA   #$C0     ;prepare to check internal C8 ROM (where is this called from?)
 1136-   A0 15       LDY   #$15
 1138-   8D F9 13    STA   $13F9
@@ -143,7 +144,7 @@ Partial disassembly and comments by Nick Westgate (and CiderPress).
 1147-   8D 66 14    STA   $1466    ;(STA $C006)
 114A-   8C 65 14    STY   $1465
 114D-   A9 C8       LDA   #$C8
-114F-   D0 93       BNE   $10E4    ;set up addresses for internal C8 ROM
+114F-   D0 93       BNE   $10E4    ;set up addresses for internal C8 ROM and test
 
 1151-   A0 03       LDY   #$03     ;SmartWatch not found
 1153-   B9 97 11    LDA   $1197,Y  ;restore ProDOS date/time
diff --git a/source/Memory.cpp b/source/Memory.cpp
index 03a22516..fd1da43a 100644
--- a/source/Memory.cpp
+++ b/source/Memory.cpp
@@ -390,7 +390,7 @@ static BYTE __stdcall IOWrite_C07x(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULON
 	case 0xB:	return IO_Null(pc, addr, bWrite, d, nCyclesLeft);
 	case 0xC:	return IO_Null(pc, addr, bWrite, d, nCyclesLeft);
 //	case 0xD:	return IO_Null(pc, addr, bWrite, d, nCyclesLeft);
-	case 0xD:	// No Slot Clock Hack for ProDOS
+	case 0xD:	// Clock Hack for ProDOS (NB. Not for NoSlotClock)
 #if CLOCK_HACK_PRODOS
 		Clock_Generic_UpdateProDos();	
 #endif
@@ -469,6 +469,14 @@ BYTE __stdcall IO_Annunciator(WORD programcounter, WORD address, BYTE write, BYT
 		return 0;
 }
 
+inline bool IsPotentialNoSlotClockAccess(const WORD address)
+{
+	// Ref: Sather UAIIe 5-28
+	const BYTE AddrHi = address >>  8;
+	return ( ((!SW_SLOTCXROM || !SW_SLOTC3ROM) && (AddrHi == 0xC3)) ||	// Internal ROM at [$C100-CFFF or $C300-C3FF] && AddrHi == $C3
+			  (!SW_SLOTCXROM && (AddrHi == 0xC8)) );					// Internal ROM at [$C100-CFFF]               && AddrHi == $C8
+}
+
 // Enabling expansion ROM ($C800..$CFFF]:
 // . Enable if: Enable1 && Enable2
 // . Enable1 = I/O SELECT' (6502 accesses $Csxx)
@@ -551,7 +559,7 @@ BYTE __stdcall IORead_Cxxx(WORD programcounter, WORD address, BYTE write, BYTE v
 		}
 	}
 
-	if ((address >= 0xC300) && (address <= 0xC3FF))
+	if (IsPotentialNoSlotClockAccess(address))
 	{
 		int data = 0;
 		if (g_NoSlotClock.Read(address, data))
@@ -585,7 +593,7 @@ BYTE __stdcall IORead_Cxxx(WORD programcounter, WORD address, BYTE write, BYTE v
 
 BYTE __stdcall IOWrite_Cxxx(WORD programcounter, WORD address, BYTE write, BYTE value, ULONG nCyclesLeft)
 {
-	if ((address >= 0xC300) && (address <= 0xC3FF))
+	if (IsPotentialNoSlotClockAccess(address))
 	{
 		g_NoSlotClock.Write(address);
 	}