diff --git a/ReadMe.txt b/ReadMe.txt
index c920f793..003c1230 100644
--- a/ReadMe.txt
+++ b/ReadMe.txt
@@ -122,6 +122,9 @@ ROM version:
     - FDU.COM
     - XM.COM
     - RTC.COM
+    - FAT.COM
+    - TIMER.COM
+    - INTTEST.COM
 
 UNA Hardware BIOS
 -----------------
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 36a35b15..6ce54737 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -268,14 +268,16 @@ HBX_INVOKE:
 	LD	A,(HB_CURBNK)		; GET CURRENT BANK
 	LD	(HB_INVBNK),A		; SAVE INVOCATION BANK
 
-	LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM FOR BANK SWITCH
+	;LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM FOR BANK SWITCH
+	LD	SP,HBX_BUF_END		; BORROW HBX_BUF FOR TEMP STACK
 	LD	A,BID_BIOS		; HBIOS BANK
 	CALL	HBX_BNKSEL		; SELECT IT
 	LD	SP,HB_STACK		; NOW USE FULL HBIOS STACK IN HBIOS BANK
 
 	CALL	HB_DISPATCH		; CALL HBIOS FUNCTION DISPATCHER
 
-	LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM FOR BANK SWITCH
+	;LD	SP,HBX_TMPSTK		; USE SMALL TEMP STACK FRAME IN HI MEM FOR BANK SWITCH
+	LD	SP,HBX_BUF_END		; BORROW HBX_BUF FOR TEMP STACK
 	PUSH	AF			; SAVE AF (FUNCTION RETURN)
 
 	LD	A,(HB_INVBNK)		; LOAD ORIGINAL BANK
@@ -636,6 +638,7 @@ HBX_INTFILL	.EQU	(HBX_XFC - HBX_BUFSIZ - $)
 ; INTERBANK COPY BUFFER (64 BYTES)
 ;
 HBX_BUF		.FILL	HBX_BUFSIZ,0
+HBX_BUF_END	.EQU	$
 ;
 ; HBIOS PROXY MGMT BLOCK (TOP 32 BYTES)
 ;