diff --git a/blk/811 b/blk/811
index 2ed76c5..0331930 100644
--- a/blk/811
+++ b/blk/811
@@ -4,8 +4,8 @@ ORG @ 0x25 + HERE ! ( bypass BPB )
 L1 FSET ( start )
 CLI, CLD, AX 0x800 MOVxI, DS AX MOVsx, ES AX MOVsx,
 SS AX MOVsx, STI,
-AH 2 MOVri, DX 0 MOVxI, CH 0 MOVri, CL 2 MOVri, AL 12 MOVri,
-BX 0 MOVxI, 0x13 INT, ( read sectors 2-14 of boot floppy )
+AH 2 MOVri, DX 0 MOVxI, CH 0 MOVri, CL 2 MOVri, AL 15 MOVri,
+BX 0 MOVxI, 0x13 INT, ( read sectors 2-15 of boot floppy )
 ( TODO: reading 12 sectors like this probably doesn't work
   on real vintage PC/AT with floppy. Make this more robust. )
 0x800 0 JMPf,
diff --git a/recipes/pcat/Makefile b/recipes/pcat/Makefile
index 6c6394c..d1467ec 100644
--- a/recipes/pcat/Makefile
+++ b/recipes/pcat/Makefile
@@ -13,13 +13,14 @@ os.bin: xcomp.fs $(STAGE)
 
 disk.bin: mbr.bin os.bin
 	cat mbr.bin os.bin > $@
+	dd if=$(EDIR)/blkfs of=$@ bs=512 seek=16
 
 $(STAGE):
 	$(MAKE) -C $(EDIR) stage
 
 .PHONY: emul
 emul: $(TARGET)
-	qemu-system-i386 -fda $(TARGET)
+	qemu-system-i386 -drive file=$(TARGET),if=floppy,format=raw
 
 .PHONY: clean
 clean:
diff --git a/recipes/pcat/xcomp.fs b/recipes/pcat/xcomp.fs
index 4a6bf9b..5194c8b 100644
--- a/recipes/pcat/xcomp.fs
+++ b/recipes/pcat/xcomp.fs
@@ -10,11 +10,46 @@ CODE (emit) 1 chkPS,
     AX POPx, AH 0x0e MOVri, ( print char ) 0x10 INT,
 ;CODE
 CODE (key)
-    AH AH XORrr, 0x16 INT, AH AH XORrr, AX PUSHx, ;CODE
+    AH AH XORrr, 0x16 INT, AH AH XORrr, AX PUSHx,
+;CODE
+CODE 13H08H ( driveno -- cx )
+    DI POPx, DX PUSHx, ( protect ) DX DI MOVxx, AX 0x800 MOVxI,
+    DI DI XORxx, ES DI MOVsx,
+    0x13 INT, DX POPx, ( unprotect ) CX PUSHx,
+    DI 0x800 MOVxI, ES DI MOVsx,
+;CODE
+CODE 13H ( ax bx cx dx -- ax bx cx dx )
+    SI POPx, ( DX ) CX POPx, BX POPx, AX POPx,
+    DX PUSHx, ( protect ) DX SI MOVxx, DI DI XORxx,
+    0x13 INT, SI DX MOVxx, DX POPx, ( unprotect )
+    AX PUSHx, BX PUSHx, CX PUSHx, SI PUSHx,
+;CODE
+: FDSPT 0x70 RAM+ ;
+: _ ( dest secno )
+    ( AH=read sectors, AL=1 sector, BX=dest,
+      CH=trackno CL=secno DH=head. )
+    0x0201 ROT ROT ( AX BX sec )
+    FDSPT @ /MOD ( AX BX sec trk )
+    2 /MOD ( AX BX sec head trk )
+    8 LSHIFT ROT OR 1+ ( AX BX head CX )
+    SWAP 8 LSHIFT ( AX BX CX DX )
+    13H 2DROP 2DROP
+;
+: FD@
+    2 * 16 + ( blkfs starts at sector 16 )
+    BLK( OVER _ BLK( 0x200 + SWAP 1+ _ ;
+: FD! DROP ;
+: FD$
+    ( get number of sectors per track with command 08H. )
+    0 13H08H 0x3f AND FDSPT !
+;
 380 LOAD  ( xcomp core high )
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
+," BLK$ FD$ "
+," ' FD@ BLK@* ! "
+," ' FD! BLK!* ! "
 EOT,
 ORG @ 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!