imul8xe.s

@@ -1,75 +0,0 @@
-FR0    = $d4 ; float48
-PORTB = $d301
-
-
-EXTENDED_RAM = $4000 ; 16KiB bank on the XE
-
-; lookup table for top byte -> PORTB value for bank-switch
-.align 256
-bankswitch:
-    .repeat 256, i
-        .byte ((i & $c0) >> 5) | $c1
-    .endrepeat
-
-; 58-77 cycles
-; clobbers x, y, dest to dest + 3
-.macro imul8xe dest, arg1, arg2
-.local done
-.local output
-.local ptr
-
-    output = dest
-    ptr = dest + 2 ; scratch space assumed
-
-    ; bottom 14 bits except the LSB are the per-bank table index
-    ; add $4000 for the bank pointer
-    lda arg1     ; 3 cyc
-    and #$fe     ; 2 cyc
-    sta ptr      ; 3 cyc
-    lda arg2     ; 3 cyc
-    and #$3f     ; 2 cyc
-    clc          ; 2 cyc
-    adc #$40     ; 2 cyc
-    sta ptr + 1  ; 3 cyc
-    
-    ; top 2 bits are the table bank selector
-    ldx arg2          ; 3 cyc
-    lda bank_switch,x ; 4 cyc
-    sta PORTB         ; 4 cyc
-
-
-    ; copy the entry into output
-    ldy #0       ; 2 cyc
-    lda (ptr),y  ; 5 cyc
-    sta output   ; 3 cyc
-    iny          ; 2 cyc
-    lda (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
-    ; if we need to use them anywhere else
-    ;;; restore memory
-    ;;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 the second param one last time for the skipped bit
-    clc          ; 2 cyc
-    lda arg2     ; 3 cyc
-    adc output   ; 3 cyc
-    sta output   ; 3 cyc
-    lda #0       ; 2 cyc
-    adc output+1 ; 3 cyc
-    sta output+1 ; 3 cyc
-
-done:
-.endmacro
-
-proc imul8xe_init
-    rts
-endproc

mandel.s

@@ -372,59 +372,51 @@ fill_masks:
     .local under256
     .local next
     .local small_product
-    ; circa 92 cycles? this doesn't seem right
-    ; 81-92 cycles
     .scope
         mul_factor_a   = arg1
         mul_factor_x   = arg2
         mul_product_lo = dest
         mul_product_hi = dest + 1
 
-        lda mul_factor_a      ; 3 cyc
+        lda mul_factor_a      ; setup: 6 cycles
+        ;ldx mul_factor_x
 
-        ; (a + x)^2/2
+        clc                   ; (a + x)^2/2: 23 cycles
-        clc                   ; 2 cyc         
+        adc mul_factor_x
-        adc mul_factor_x      ; 3 cyc
+        tax
-        tax                   ; 2 cyc
+        bcc under256
-        bcc under256          ; 2 cyc
+        lda mul_hibyte512,x
-        lda mul_hibyte512,x   ; 4 cyc
+        bcs next
-        bcs next              ; 2 cyc
     under256:
-        lda mul_hibyte256,x   ; 4 cyc
+        lda mul_hibyte256,x
-        sec                   ; 2 cyc
+        sec
     next:
-        sta mul_product_hi    ; 3 cyc
+        sta mul_product_hi
-        lda mul_lobyte256,x   ; 4 cyc
+        lda mul_lobyte256,x
 
-        ; - a^2/2
+        ldx mul_factor_a      ; - a^2/2: 20 cycles
-        ldx mul_factor_a      ; 3 cyc
+        sbc mul_lobyte256,x
-        sbc mul_lobyte256,x   ; 4 cyc
+        sta mul_product_lo
-        sta mul_product_lo    ; 3 cyc
+        lda mul_product_hi
-        lda mul_product_hi    ; 3 cyc
+        sbc mul_hibyte256,x
-        sbc mul_hibyte256,x   ; 4 cyc
+        sta mul_product_hi
-        sta mul_product_hi    ; 3 cyc
 
-        ; + x & a & 1:
+        ldx mul_factor_x      ; + x & a & 1: 22 cycles
-        ; (this is a kludge to correct a
+        txa                   ; (this is a kludge to correct a
-        ; roundoff error that makes odd * odd too low)
+        and mul_factor_a      ; roundoff error that makes odd * odd too low)
-        ldx mul_factor_x      ; 3 cyc
+        and #1
-        txa                   ; 2 cyc
-        and mul_factor_a      ; 3 cyc
-        and #1                ; 2 cyc
 
-        clc                   ; 2 cyc
+        clc
-        adc mul_product_lo    ; 3 cyc
+        adc mul_product_lo
-        bcc small_product     ; 2 cyc
+        bcc small_product
-        inc mul_product_hi    ; 5 cyc
+        inc mul_product_hi
-
-        ; - x^2/2
     small_product:
-        sec                   ; 2 cyc
+        sec                   ; - x^2/2: 25 cycles
-        sbc mul_lobyte256,x   ; 4 cyc
+        sbc mul_lobyte256,x
-        sta mul_product_lo    ; 3 cyc
+        sta mul_product_lo
-        lda mul_product_hi    ; 3 cyc
+        lda mul_product_hi
-        sbc mul_hibyte256,x   ; 4 cyc
+        sbc mul_hibyte256,x
-        sta mul_product_hi    ; 3 cyc
+        sta mul_product_hi
     .endscope
 .endmacro