diff --git a/mandel-core.s b/mandel-core.s
index 1f7234b..5159e2f 100644
--- a/mandel-core.s
+++ b/mandel-core.s
@@ -593,7 +593,9 @@ bank_switch_table:
 .macro imul8 dest, arg1, arg2, xe
     .if xe
         ; using 64KB lookup table
-        ; 52-69 cycles
+        ; 50-55 cycles
+        ; min: 11 + 9 + 9 + 21 = 50
+        ; max: 11 + 9 + 9 + 26 = 55
         ; clobbers x, y, dest, ptr
         .scope
             output = dest
@@ -612,15 +614,36 @@ bank_switch_table:
             ora #$40     ; 2 cyc
             sta ptr + 1  ; 3 cyc
 
-            ; copy the entry into output
+            ; mask off the low bit for the index, as the table contains
+            ; entries for every other arg1 value...
             lda arg1     ; 3 cyc
-            and #$fe     ; 2 cyc
             tay          ; 2 cyc
-            lda (ptr),y  ; 5 cyc
-            sta output   ; 3 cyc
-            iny          ; 2 cyc
-            lda (ptr),y  ; 5 cyc
-            sta output+1 ; 3 cyc
+            and #1       ; 2 cyc
+            bne odd      ; 2 cyc
+
+        even:
+            ; copy the entry into output
+            lda (ptr),y    ; 5 cyc
+            sta output     ; 3 cyc
+            iny            ; 2 cyc
+            lda (ptr),y    ; 5 cyc
+            sta output + 1 ; 3 cyc
+            jmp done       ; 3 cyc
+
+        odd:
+
+            ; skip the LSB for the index
+            dey            ; 2 cyc
+
+            ; add arg2 one last time for the skipped bit
+            txa            ; 2 cyc
+            clc            ; 2 cyc
+            adc (ptr), y   ; 5 cyc
+            sta output     ; 3 cyc
+            lda #0         ; 2 cyc
+            iny            ; 2 cyc
+            adc (ptr),y    ; 5 cyc
+            sta output + 1 ; 3 cyc
 
             ; note: we are not restoring memory to save 6 cycles!
             ; this means those 16kb have to be switched back to base RAM
@@ -629,18 +652,6 @@ bank_switch_table:
             ;;lda #$81     ; 2 cyc - disabled
             ;;sta PORTB    ; 4 cyc - disabled
 
-            ; check that 1 bit we skipped to fit into space
-            lda arg1     ; 3 cyc
-            and #1       ; 2 cyc
-            beq done     ; 2 cyc
-
-            ; add arg2 one last time for the skipped bit
-            clc          ; 2 cyc
-            txa          ; 2 cyc
-            adc output   ; 3 cyc
-            sta output   ; 3 cyc
-            add_carry output + 1 ; 2-7 cyc
-
         done:
         .endscope
     .else
@@ -776,8 +787,8 @@ inner_loop:
 
 ; min base mem: 81 * 4 + 22 * 2 + 10 + 6 = 384 cyc
 ; max base mem: 92 * 4 + 27 * 2 + 50 + 6 = 478 cyc
-; min ext-mem: 52 * 4 + 22 * 2 + 10 + 6 = 268 cyc
-; max ext-mem: 69 * 4 + 27 * 2 + 50 + 6 = 386 cyc
+; min ext-mem: 50 * 4 + 22 * 2 + 10 + 6 = 260 cyc
+; max ext-mem: 55 * 4 + 27 * 2 + 50 + 6 = 330 cyc
 .macro imul16_impl xe
     .local arg1
     .local arg2
@@ -796,18 +807,18 @@ inner_loop:
     ; h1*h2*256*256 + h1*l2*256 + h2*l1*256 + l1*l2
 
     ; l1 * l2
-    imul8 result, arg1, arg2, xe        ; 81-92 or 52-69
+    imul8 result, arg1, arg2, xe        ; 81-92 or 50-55
 
     ; 256 * 256 * h1 * h2
-    imul8 result + 2, arg1 + 1, arg2 + 1, xe ; 81-92 or 52-69
+    imul8 result + 2, arg1 + 1, arg2 + 1, xe ; 81-92 or 50-55
 
     ; 256 * h1 * l1
-    imul8 inter, arg1 + 1, arg2, xe     ; 81-92 or 52-69
+    imul8 inter, arg1 + 1, arg2, xe     ; 81-92 or 50-55
     add16 result + 1, result + 1, inter ; 20 cyc
     add_carry result + 3                ; 2-7 cyc
 
     ; 256 * l1 * h2
-    imul8 inter, arg1, arg2 + 1, xe     ; 81-92 or 52-69
+    imul8 inter, arg1, arg2 + 1, xe     ; 81-92 or 50-55
     add16 result + 1, result + 1, inter ; 20 cyc
     add_carry result + 3                ; 2-7 cyc
 
@@ -828,8 +839,8 @@ arg2_pos:
 
 ; min base ram: 5 + 19 * 2 + 81 + 22 * 2 + 6 = 174
 ; max base ram: 23 + 19 * 2 + 92 + 27 * 2 + 6 = 213
-; min ext ram: 5 + 19 * 2 + 52 + 22 * 2 + 6 = 145
-; max ext ram: 23 + 19 * 2 + 69 + 27 * 2 + 6 = 190
+; min ext ram: 5 + 19 * 2 + 50 + 22 * 2 + 6 = 143
+; max ext ram: 23 + 19 * 2 + 55 + 27 * 2 + 6 = 176
 .macro sqr16_impl xe
     .scope
         arg = FR0    ; 16-bit arg (clobbered)
@@ -855,7 +866,7 @@ arg2_pos:
         sqr8 result + 2, arg + 1  ; 19 cyc
 
         ; 2 * h * l * 256
-        imul8 inter, arg + 1, arg, xe        ; 81-92 / 52-69 cyc
+        imul8 inter, arg + 1, arg, xe        ; 81-92 / 50-55 cyc
         add16 result + 1, result + 1, inter  ; 20 cyc
         add_carry result + 3                 ; 2-7 cyc
         add16 result + 1, result + 1, inter  ; 20 cyc