From 27995007c5da6b259069bf7147d0ce19c25125a9 Mon Sep 17 00:00:00 2001
From: Brooke Vibber <bvibber@pobox.com>
Date: Sat, 22 Aug 2026 15:25:58 -0700
Subject: [PATCH] experiment

---
 mandel-core.s | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/mandel-core.s b/mandel-core.s
index a153ff5..69980b8 100644
--- a/mandel-core.s
+++ b/mandel-core.s
@@ -592,7 +592,7 @@ bank_switch_table:
 .macro imul8 dest, arg1, arg2, xe
     .if xe
         ; using 64KB lookup table
-        ; 51-70 cycles
+        ; 52-69 cycles
         ; clobbers x, y, dest, ptr
         .scope
             output = dest
@@ -636,9 +636,7 @@ bank_switch_table:
             txa          ; 2 cyc
             adc output   ; 3 cyc
             sta output   ; 3 cyc
-            lda #0       ; 2 cyc
-            adc output+1 ; 3 cyc
-            sta output+1 ; 3 cyc
+            add_carry output + 1 ; 2-7 cyc
 
         done:
         .endscope
@@ -775,8 +773,8 @@ 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: 51 * 4 + 22 * 2 + 10 + 6 = 264 cyc
-; max ext-mem: 70 * 4 + 27 * 2 + 50 + 6 = 390 cyc
+; min ext-mem: 52 * 4 + 22 * 2 + 10 + 6 = 268 cyc
+; max ext-mem: 69 * 4 + 27 * 2 + 50 + 6 = 386 cyc
 .macro imul16_impl xe
     .local arg1
     .local arg2
@@ -794,15 +792,15 @@ inner_loop:
     ; h1*256*(h2*256 + l2) + l1*(h2*256 + l2)
     ; h1*h2*256*256 + h1*l2*256 + h2*l1*256 + l1*l2
 
-    imul8 result, arg1, arg2, xe        ; 81-92 or 51-70
+    imul8 result, arg1, arg2, xe        ; 81-92 or 52-69
 
-    imul8 result + 2, arg1 + 1, arg2 + 1, xe ; 81-92 or 51-70
+    imul8 result + 2, arg1 + 1, arg2 + 1, xe ; 81-92 or 52-69
 
-    imul8 inter, arg1 + 1, arg2, xe     ; 81-92 or 51-70
+    imul8 inter, arg1 + 1, arg2, xe     ; 81-92 or 52-69
     add16 result + 1, result + 1, inter ; 20 cyc
     add_carry result + 3                ; 2-7 cyc
 
-    imul8 inter, arg1, arg2 + 1, xe     ; 81-92 or 51-70
+    imul8 inter, arg1, arg2 + 1, xe     ; 81-92 or 52-69
     add16 result + 1, result + 1, inter ; 20 cyc
     add_carry result + 3                ; 2-7 cyc
 
@@ -823,8 +821,8 @@ 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 + 51 + 22 * 2 + 6 = 144
-; max ext ram: 23 + 19 * 2 + 70 + 27 * 2 + 6 = 191
+; min ext ram: 5 + 19 * 2 + 52 + 22 * 2 + 6 = 145
+; max ext ram: 23 + 19 * 2 + 69 + 27 * 2 + 6 = 190
 .macro sqr16_impl xe
     .scope
         arg = FR0    ; 16-bit arg (clobbered)
@@ -847,7 +845,7 @@ arg2_pos:
 
         sqr8 result + 2, arg + 1  ; 19 cyc
 
-        imul8 inter, arg + 1, arg, xe        ; 81-92 / 51-70 cyc
+        imul8 inter, arg + 1, arg, xe        ; 81-92 / 52-69 cyc
         add16 result + 1, result + 1, inter  ; 20 cyc
         add_carry result + 3                 ; 2-7 cyc
         add16 result + 1, result + 1, inter  ; 20 cyc