diff --git a/blk/730 b/blk/730
index 903d983..56e8271 100644
--- a/blk/730
+++ b/blk/730
@@ -2,15 +2,15 @@
 
 Work in progress. Load with "750 LOAD".
 
+Mnemonics are followed by argument types. For example, MOVri,
+moves 8-bit immediate to 8-bit register.
 
+'r' = 8-bit register           'x' = 16-bit register
+'i' = immediate, size depends on other operand.
+'s' = SREG register
 
+Mnemonics that only have one signature (for example INT,) don't
+have operands letters.
 
-
-
-
-
-
-
-
-
+For jumps, it's special. 's' is SHORT, 'n' is NEAR, 'f' is FAR.
 
diff --git a/blk/751 b/blk/751
index 26ad59c..206a609 100644
--- a/blk/751
+++ b/blk/751
@@ -3,6 +3,6 @@ CREATE BIN( 0 , : BIN(+ BIN( @ + ;
 VARIABLE L1 VARIABLE L2 VARIABLE L3 VARIABLE L4
 : AL 0 ; : CL 1 ; : DL 2 ; : BL 3 ;
 : AH 4 ; : CH 5 ; : DH 6 ; : BH 7 ;
-: AX 8 ; : CX 9 ; : DX 10 ; : BX 11 ;
-: SP 12 ; : BP 13 ; : SI 14 ; : DI 15 ;
+: AX 0 ; : CX 1 ; : DX 2 ; : BX 3 ;
+: SP 4 ; : BP 5 ; : SI 6 ; : DI 7 ;
 : ES 0 ; : CS 1 ; : SS 2 ; : DS 3 ;
diff --git a/blk/752 b/blk/752
index ba65af0..b70ebe0 100644
--- a/blk/752
+++ b/blk/752
@@ -4,5 +4,3 @@
 ;
 : PC H@ ORG @ - BIN( @ + ;
 : A, C, ;
-( dst8 src8 -- modrm )
-: MODRMrr 0x7 AND 3 LSHIFT SWAP 0x7 AND OR 0xc0 OR ;
diff --git a/blk/753 b/blk/753
index ed9f937..3d94270 100644
--- a/blk/753
+++ b/blk/753
@@ -4,9 +4,9 @@
 ( no argument, jumps with abs addrs are special )
 0xeb OP1 JMPs,       0xe9 OP1 JMPn,      0x74 OP1 JZ,
 : MOVri, SWAP 0xb0 OR A, A, ;
-: MOVrI, SWAP 0xb0 OR A, SPLITB A, A, ;
-: MOVsx, 0x8e A, SWAP MODRMrr A, ;
+: MOVxi, SWAP 0xb8 OR A, SPLITB A, A, ;
+: MOVsx, 0x8e A, SWAP 3 LSHIFT OR 0xc0 OR A, ;
 : INT, 0xcd A, A, ;
 : JMPr, 0xff A, 7 AND 0xe0 OR A, ;
-: ORrr, 0x08 A, MODRMrr A, ;
-: XORxx, 0x31 A, MODRMrr A, ;
+: OPrr CREATE C, DOES> C@ A, 3 LSHIFT OR 0xc0 OR A, ;
+0x31 OPrr XORxx,     0x08 OPrr ORrr,
diff --git a/blk/811 b/blk/811
index 1b8d2e7..9007b24 100644
--- a/blk/811
+++ b/blk/811
@@ -3,8 +3,8 @@ JMPs, L1 FWRs ( start )
 ORG @ 0x25 + HERE ! ( bypass BPB )
 L1 FSET ( start )
 CLI, CLD, AX AX XORxx, DS AX MOVsx, ES AX MOVsx,
-SS AX MOVsx, SP 0xffff MOVrI, STI,
-AH 2 MOVri, DX 0 MOVrI, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
-BX 0x8000 MOVrI, 0x13 INT, ( read 2nd sector of boot floppy )
+SS AX MOVsx, SP 0xffff MOVxi, STI,
+AH 2 MOVri, DX 0 MOVxi, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
+BX 0x8000 MOVxi, 0x13 INT, ( read 2nd sector of boot floppy )
 BX JMPr,
 ORG @ 0x1fe + HERE ! 0x55 A, 0xaa A,
diff --git a/blk/812 b/blk/812
index 768fb96..a109fef 100644
--- a/blk/812
+++ b/blk/812
@@ -2,7 +2,7 @@ H@ ORG ! 0x8000 BIN( !
 JMPs, L1 FWRs ( start )
 L2 ( msg ) BSET ," Hello World!" 0 A,
 L1 FSET ( start )
-SI L2 @ ( msg ) MOVrI, AH 0x0e MOVri, ( print char )
+SI L2 @ ( msg ) MOVxi, AH 0x0e MOVri, ( print char )
 L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
 JZ, L2 FWRs ( next ) 0x10 INT, ( print char )
 JMPs, L1 ( loop ) BWR