flip the y coordinate sign

currently using 3.13 precision to output to floats for formatting

mandel.s

@@ -1,16 +1,16 @@
 ; Our zero-page vars
-ox              = $80 ; fixed8.24: center point x
-oy              = $84 ; fixed8.24: center point y
-cx              = $88 ; fixed8.24: c_x
-cy              = $8c ; fixed8.24: c_y
+ox              = $80 ; fixed6.26: center point x
+oy              = $84 ; fixed6.26: center point y
+cx              = $88 ; fixed6.26: c_x
+cy              = $8c ; fixed6.26: c_y
 
-zx              = $90 ; fixed8.24: z_x
-zy              = $94 ; fixed8.24: z_y
-zx_2            = $98 ; fixed8.24: z_x^2
-zy_2            = $9c ; fixed8.24: z_y^2
+zx              = $90 ; fixed6.26: z_x
+zy              = $94 ; fixed6.26: z_y
+zx_2            = $98 ; fixed6.26: z_x^2
+zy_2            = $9c ; fixed6.26: z_y^2
 
-zx_zy           = $a0 ; fixed8.24: z_x * z_y
-dist            = $a4 ; fixed8.24: z_x^2 + z_y^2
+zx_zy           = $a0 ; fixed6.26: z_x * z_y
+dist            = $a4 ; fixed6.26: z_x^2 + z_y^2
 sx              = $a8 ; i16: screen pixel x
 sy              = $aa ; i16: screen pixel y
 z_buffer_active = $ac ; boolean: 1 if we triggered the lake, 0 if not
@@ -31,10 +31,12 @@ chroma_offset   = $bb ; u8
 palette_ticks   = $bc ; u8
 chroma_ticks    = $bd ; u8
 count_frames    = $be ; u8
-count_pixels    = $bf ; u8
+; free space $bf
 
-total_pixels    = $c0 ; float48
-total_ms        = $c6 ; float48
+count_iters     = $c0 ; u16
+text_col        = $c2 ; u8
+text_row        = $c3 ; u8
+; free space c4-cb
 temp            = $cc ; u16
 temp2           = $ce ; u16
 
@@ -59,10 +61,12 @@ LBUFF  = $0580 ; result buffer for FASC routine
 ; FP ROM routine vectors
 FASC   = $D8E6 ; FLOATING POINT TO ASCII (output in INBUFF, last char has high bit set)
 IFP    = $D9AA ; INTEGER TO FLOATING POINT CONVERSION (FR0:u16 -> FR0:float48)
+FPI    = $D9D2 ; floating point to integer
 FADD   = $DA66 ; ADDITION       (FR0 += FR1)
 FSUB   = $DA60 ; SUBTRACTION    (FR0 -= FR1)
 FMUL   = $DADB ; MULTIPLICATION (FR0 *= FR1)
 FDIV   = $DB28 ; DIVISION       (FR0 /= FR1)
+ZFR0   = $DA44 ; clear FR0
 ZF1    = $DA46 ; CLEAR ZERO PAGE FLOATING POINT NUMBER (XX)
 FLD0R  = $DD89 ; LOAD FR0 WITH FLOATING POINT NUMBER (YYXX)
 FLD1R  = $DD98 ; LOAD FR1 WITH FLOATING POINT NUMBER (YYXX)
@@ -76,7 +80,7 @@ framebuffer_bottom = $b000
 display_list       = $bf00
 framebuffer_end    = $c000
 
-height = 184
+height = 176
 half_height = height >> 1
 width = 160
 half_width = width >> 1
@@ -140,25 +144,52 @@ strings:
 str_self:
     .byte "MANDEL-6502"
 str_self_end:
+    .byte 0
 str_speed:
-    .byte " ms/px"
+    .byte "us/iter: "
 str_speed_end:
+    .byte 0
 str_run:
     .byte " RUN"
 str_run_end:
+    .byte 0
 str_done:
     .byte "DONE"
 str_done_end:
+    .byte 0
+str_padding:
+    .byte "      "
+str_padding_end:
+    .byte 0
 
-str_self_len = str_self_end - str_self
 str_speed_len = str_speed_end - str_speed
 str_run_len = str_run_end - str_run
 str_done_len = str_done_end - str_done
-speed_precision = 6
+str_padding_len = str_padding_end - str_padding
 
-speed_start = 40 - str_done_len - str_speed_len - speed_precision - 1
-speed_len = 14 + str_speed_len
+speed_start = 40 - str_done_len - str_speed_len - str_padding_len - 1
 
+col_x = 1
+str_x:
+    .byte "X:"
+    .byte 0
+str_x_len = 2
+str_x_space = 12
+str_x_padding = 2
+
+col_y = col_x + str_x_len + str_x_space + str_x_padding
+str_y:
+    .byte "Y:"
+    .byte 0
+str_y_len = 2
+str_y_space = 12
+str_y_padding = 2
+
+col_zoom = col_y + str_y_len + str_y_space + str_y_padding
+str_zoom:
+    .byte "ZOOM:"
+    .byte 0
+str_zoom_len = 5
 
 char_map:
     ; Map ATASCII string values to framebuffer font entries
@@ -189,20 +220,49 @@ aspect:
     ;
     ; 184h is the equiv of 220.8h at square pixels
     ; 320 / 220.8 = 1.45 display aspect ratio
-aspect_x: ; fixed4.16 5/4
-    .word 5 << (12 - 2)
+aspect_x: ; fixed3.13 5/4
+    .word 5 << (13 - 2)
 
-aspect_y: ; fixed4.16 3/4
-    .word 3 << (12 - 2)
+aspect_y: ; fixed3.13 3/4
+    .word 3 << (13 - 2)
 
-ms_per_frame: ; float48 16.66666667
-    .byte 64  ; exponent/sign
-    .byte $16 ; BCD digits
+fixed3_13_as_float: ; float48
+    ; 1 << 13
+    ; 8192
+    ; 81 92 . 00 00 00
+    .byte 65 ; exponent/sign - +1 byte
+    .byte $81
+    .byte $92
+    .byte $00
+    .byte $00
+    .byte $00
+
+sec_per_frame: ; float48 00 . 01 66 66 66 67
+    .byte 63  ; exponent/sign - -1 bytes
+    .byte $01 ; BCD digits
     .byte $66
     .byte $66
     .byte $66
     .byte $67
 
+us_per_sec: ; float48 1e9 01 00 0,0 00 . 00
+    .byte 67  ; exponent/sign +3 bytes
+    .byte $01 ; BCD digits
+    .byte $00
+    .byte $00
+    .byte $00
+    .byte $00
+
+total_iters: ; float48
+    .repeat 6
+        .byte 0
+    .endrepeat
+
+total_sec: ; float48
+    .repeat 6
+        .byte 0
+    .endrepeat
+
 display_list_start:
     ; 24 lines overscan
     .repeat 3
@@ -226,6 +286,10 @@ display_list_start:
         .byte $0e
     .endrep
 
+    ; 8 scan lines, 1 row of 40-column text
+    .byte $42
+    .addr textbuffer + 40
+
     .byte $41 ; jump and blank
     .addr display_list
 display_list_end:
@@ -234,9 +298,9 @@ display_list_len = display_list_end - display_list_start
 color_map:
     .byte 0
     .repeat 85
-        .byte 1
-        .byte 2
-        .byte 3
+        .byte %01010101
+        .byte %10101010
+        .byte %11111111
     .endrepeat
 
 
@@ -285,23 +349,34 @@ fill_masks:
     .byte %00000001
     .byte %00000000
 
+pixel_masks:
+    .byte %11111111
+    .byte %11110000
+    .byte %11000000
+
 viewport_zoom:
-    .byte 1
-    .byte 6
-    .byte 8
-    .byte 6
+    .byte 0
+    .byte 5
+    .byte 7
+    .byte 5
+    .byte 7
+    .byte 7
 
 viewport_ox:
-    .dword $00000000
-    .dword $ff110000
-    .dword $ff110000
-    .dword $fe400000
+    .dword ($00000000 & $3fffffff) << 2
+    .dword ($ff110000 & $3fffffff) << 2
+    .dword ($ff110000 & $3fffffff) << 2
+    .dword ($fe400000 & $3fffffff) << 2
+    .dword ($fe3b0000 & $3fffffff) << 2
+    .dword $fd220000
 
 viewport_oy:
-    .dword $00000000
-    .dword $ffb60000
-    .dword $ffbe0000
-    .dword $00000000
+    .dword ($00000000 & $3fffffff) << 2
+    .dword ($ffb60000 & $3fffffff) << 2
+    .dword ($ffbe0000 & $3fffffff) << 2
+    .dword ($00000000 & $3fffffff) << 2
+    .dword ($fffe0000 & $3fffffff) << 2
+    .dword $ff000000
 
 ; 2 + 9 * byte cycles
 .macro add bytes, dest, arg1, arg2
@@ -453,20 +528,6 @@ viewport_oy:
     sta dest + 1
 .endmacro
 
-; input: arg as u8
-; input/output: dest as u16
-; clobbers a, x
-.macro sqr8_add16 dest, arg
-    ldx arg
-    clc
-    lda sqr_lobyte,x
-    adc dest
-    sta dest
-    lda sqr_hibyte,x
-    adc dest + 1
-    sta dest + 1
-.endmacro
-
 .segment "TABLES"
 ; lookup table for top byte -> PORTB value for bank-switch
 .align 256
@@ -749,9 +810,8 @@ inner_loop:
     ; h1*h2*256*256 + h1*l2*256 + h2*l1*256 + l1*l2
 
     imul8 result, arg1, arg2, xe
-    lda #0
-    sta result + 2
-    sta result + 3
+
+    imul8 result + 2, arg1 + 1, arg2 + 1, xe
 
     imul8 inter, arg1 + 1, arg2, xe
     add16 result + 1, result + 1, inter
@@ -761,9 +821,6 @@ inner_loop:
     add16 result + 1, result + 1, inter
     add_carry result + 3
 
-    imul8 inter, arg1 + 1, arg2 + 1, xe
-    add16 result + 2, result + 2, inter
-
     ; In case of negative inputs, adjust high word
     ; https://stackoverflow.com/a/28827013
     lda arg1 + 1
@@ -796,9 +853,8 @@ arg2_pos:
         ; h*h*256*256 + h*l*256 + h*l*256 + l*l
 
         sqr8 result, arg
-        lda #0
-        sta result + 2
-        sta result + 3
+
+        sqr8 result + 2, arg + 1
 
         imul8 inter, arg + 1, arg, xe
         add16 result + 1, result + 1, inter
@@ -806,8 +862,6 @@ arg2_pos:
         add16 result + 1, result + 1, inter
         add_carry result + 3
 
-        sqr8_add16 result + 2, arg + 1
-
         rts ; 6 cyc
     .endscope
 .endmacro
@@ -873,10 +927,72 @@ next:
 
 .endmacro
 
+; input in FR0, 16 bits signed 3.13 fixed
+; output in FR0, Atari float
+; clobbers a, x, y, FR0, FR1
+.proc fixed3_13_to_float
+    ldx #.lobyte(fixed3_13_as_float)
+    ldy #.hibyte(fixed3_13_as_float)
+    jsr FLD1R
+
+    ; check sign bit! conversion routine is for unsigned
+    lda FR0 + 1
+    bpl positive
+
+negative:
+    neg16 FR0
+    jsr IFP
+
+    ; set float sign bit
+    lda FR0
+    ora #$80
+    sta FR0
+    jmp common
+
+positive:
+    jsr IFP
+
+common:
+    jsr FDIV
+    rts
+
+.endproc
+
+; input in FR0, Atari float
+; output in FR0, 16 bits signed 3.13 fixed
+; clobbers a, x, y, FR0, FR1
+.proc float_to_fixed3_13
+    ldx #.lobyte(fixed3_13_as_float)
+    ldy #.hibyte(fixed3_13_as_float)
+    jsr FLD1R
+    jsr FMUL
+
+    ; check sign bit! conversion routine is for unsigned
+    lda FR0
+    bcc positive
+
+negative:
+    ; clearfloat sign bit
+    lda FR0
+    eor #$80
+    sta FR0
+
+    jsr FPI
+    neg16 FR0
+    jmp common
+
+positive:
+    jsr FPI
+
+common:
+    rts
+
+.endproc
+
 .proc mandelbrot
     ; input:
-    ; cx: position scaled to 8.24 fixed point - -128..+127.9
-    ; cy: position scaled to 8.24
+    ; cx: position scaled to 6.26 fixed point - -32..+31.9
+    ; cy: position scaled to 6.26
     ;
     ; output:
     ; iter: iteration count at escape or 0
@@ -927,6 +1043,11 @@ next:
     sta z_buffer_end
 
 loop:
+    inc count_iters
+    bne low_iters
+    inc count_iters + 1
+low_iters:
+
     ; iter++ & max-iters break
     inc iter
     bne keep_going
@@ -934,7 +1055,7 @@ loop:
 keep_going:
 
     .macro quick_exit arg, max
-        ; arg: fixed8.24
+        ; arg: fixed6.26
         ; max: integer
         .local positive
         .local negative
@@ -947,12 +1068,12 @@ keep_going:
         bmi negative
 
     positive:
-        cmp #max
+        cmp #(max << 2)
         bmi all_done ; 'less than'
         jmp exit_path
 
     negative:
-        cmp #(256 - max)
+        cmp #(256 - (max << 2))
         beq first_equal ; 'equal' on first byte
         bpl all_done    ; 'greater than'
 
@@ -972,7 +1093,7 @@ keep_going:
     all_done:
     .endmacro
 
-    ; 8.24: (-128 .. 127.9)
+    ; 6.26: (-32 .. 31.9)
     ; zx = zx_2  - zy_2  + cx
     sub32 zx, zx_2, zy_2
     add32 zx, zx, cx
@@ -983,9 +1104,9 @@ keep_going:
     add32 zy, zy, cy
     quick_exit zy, 2
 
-    ; convert 8.24 -> 4.12: (-8 .. +7.9)
-    shift_round_16 zx, 4
-    shift_round_16 zy, 4
+    ; convert 6.26 -> 3.13: (-4 .. +3.9)
+    shift_round_16 zx, 3
+    shift_round_16 zy, 3
 
     ; zx_2 = zx * zx
     sqr16 zx_2, zx + 2
@@ -1107,9 +1228,9 @@ enough:
 .endmacro
 
 .macro zoom_factor dest, src, aspect
-    ; output: dest: fixed8.24
-    ; input: src: fixed4.12
-    ; aspect: fixed4.12
+    ; output: dest: fixed6.26
+    ; input: src: fixed3.13
+    ; aspect: fixed3.13
     ; clobbers A, X, flags, etc
     copy16 dest, src
     scale_zoom dest
@@ -1127,8 +1248,11 @@ enough:
     ; iter -> color
     ldx iter
     lda color_map,x
+    ldx fill_level
+    and pixel_masks,x
     sta pixel_color
-    lda #(255 - 3)
+    lda pixel_masks,x
+    eor #$ff
     sta pixel_mask
 
     ; sy -> line base address in temp
@@ -1177,22 +1301,23 @@ point:
     ; pixel_mask <<= pixel_shift (shifting in ones)
     and #3
     sta pixel_shift
-    lda #3
-    sec
-    sbc pixel_shift
     tax
 shift_loop:
     beq shift_done
-    asl pixel_color
-    asl pixel_color
+    lsr pixel_color
+    lsr pixel_color
     sec
-    rol pixel_mask
+    ror pixel_mask
     sec
-    rol pixel_mask
+    ror pixel_mask
     dex
     jmp shift_loop
 shift_done:
 
+    ldy fill_level
+    ldx fill_masks,y
+    inx
+
     ; pixel_offset = temp >> 2
     lda temp
     lsr a
@@ -1200,48 +1325,94 @@ shift_done:
     sta pixel_offset
     tay
 
+draw_pixel:
     ; read, mask, or, write
     lda (pixel_ptr),y
     and pixel_mask
     ora pixel_color
     sta (pixel_ptr),y
 
+    dex
+    beq done
+    clc
+    lda #40
+    adc pixel_ptr
+    sta pixel_ptr
+    lda #0
+    adc pixel_ptr + 1
+    sta pixel_ptr + 1
+    jmp draw_pixel
+
+done:
     rts
 .endproc
 
-.macro draw_text_indirect col, len, strptr
-    ; clobbers A, X
-    .local loop
-    .local done
-    ldx #0
-loop:
-    cpx #len
-    beq done
-    txa
-    tay
-    lda (strptr),y
-    tay
-    lda char_map,y
-    sta textbuffer + col,x
-    inx
-    jmp loop
-done:
-.endmacro
+; in/out: column in text_col
+; in: row in text_row
+; in: pointer to string in INBUFF
+; clobbers x/y/a/temp
+.proc draw_string
+    drawptr = temp
+    strptr = INBUFF
 
-.macro draw_text col, len, cstr
-    ; clobbers A, X
-    .local loop
-    .local done
-    ldx #0
+    clc
+    lda #.lobyte(textbuffer)
+    adc text_col
+    sta temp
+    lda #.hibyte(textbuffer)
+    adc #0
+    sta temp + 1
+
+    ldx text_row
+    beq done_rows
+continue_rows:
+    clc
+    lda temp
+    adc #40
+    sta temp
+    lda temp + 1
+    adc #0
+    sta temp + 1
+    dex
+    bne continue_rows
+
+done_rows:
+
+    ldy #0
 loop:
-    cpx #len
+    lda (strptr),y
+    ; if char's null, terminate c-style
     beq done
-    ldy cstr,x
-    lda char_map,y
-    sta textbuffer + col,x
-    inx
+    ; save the char for terminator check
+    pha
+    ; strip the high bit (terminator)
+    and #$7f
+    tax
+    lda char_map,x
+    sta (drawptr),y
+    iny
+
+    pla
+    ; _last_ char has high bit set in atari rom routines
+    bmi done
     jmp loop
+
 done:
+    ; move the text column pointer
+    tya
+    clc
+    adc text_col
+    sta text_col
+
+    rts
+.endproc
+
+.macro draw_string_const str
+    lda #.lobyte(str)
+    sta INBUFF
+    lda #.hibyte(str)
+    sta INBUFF + 1
+    jsr draw_string
 .endmacro
 
 .proc vblank_handler
@@ -1367,7 +1538,7 @@ skip_char:
 
 plus:
     lda zoom
-    cmp #8
+    cmp #7
     bpl skip_char
     inc zoom
     jmp done
@@ -1378,16 +1549,20 @@ minus:
     dec zoom
     jmp done
 up:
-    sub32 oy, oy, temp
+    add32 oy, oy, temp
+    jsr display_coords
     jmp done
 down:
-    add32 oy, oy, temp
+    sub32 oy, oy, temp
+    jsr display_coords
     jmp done
 left:
     sub32 ox, ox, temp
+    jsr display_coords
     jmp done
 right:
     add32 ox, ox, temp
+    jsr display_coords
     jmp done
 
 number_keys:
@@ -1399,6 +1574,10 @@ number_keys:
     beq three
     cpy #KEY_4
     beq four
+    cpy #KEY_5
+    beq five
+    cpy #KEY_6
+    beq six
     jmp skip_char
 
 one:
@@ -1412,6 +1591,12 @@ three:
     jmp load_key_viewport
 four:
     ldx #3
+    jmp load_key_viewport
+five:
+    ldx #4
+    jmp load_key_viewport
+six:
+    ldx #5
     ; fall through
 load_key_viewport:
     jsr load_viewport
@@ -1447,12 +1632,63 @@ zero_byte_loop:
 
 .proc status_bar
     ; Status bar
-    draw_text 0, str_self_len, str_self
-    draw_text 40 - str_run_len, str_run_len, str_run
+
+    lda #0
+    sta text_col
+    lda #0
+    sta text_row
+    draw_string_const str_self
+
+    lda #(40 - str_run_len)
+    sta text_col
+    draw_string_const str_run
 
     rts
 .endproc
 
+.proc display_coords
+    lda #1
+    sta text_row
+    lda #col_x
+    sta text_col
+    draw_string_const str_x
+
+    copy32 FR0, ox
+    shift_round_16 FR0, 3
+    copy16 FR0, FR0 + 2
+    jsr fixed3_13_to_float
+    jsr FASC
+    jsr draw_string
+
+    lda #col_y
+    sta text_col
+    draw_string_const str_y
+
+    copy32 FR0, oy
+    shift_round_16 FR0, 3
+    copy16 FR0, FR0 + 2
+    jsr fixed3_13_to_float
+    jsr FASC
+    jsr draw_string
+
+    lda #col_zoom
+    sta text_col
+    draw_string_const str_zoom
+
+    lda zoom
+    clc
+    adc #0
+    sta FR0
+    lda #0
+    sta FR0 + 1
+    jsr IFP
+    jsr FASC
+    jsr draw_string
+
+    rts
+
+.endproc
+
 ; input: viewport selector in x
 ; clobbers: a, x
 .proc load_viewport
@@ -1504,6 +1740,7 @@ zero_byte_loop:
     sta DMACTL
 
     jsr clear_screen
+    jsr display_coords
 
     ; Copy the display list into properly aligned memory
     ; Can't cross 1024-byte boundaries :D
@@ -1542,19 +1779,24 @@ copy_byte_loop:
     jsr SETVBV
 
 main_loop:
-    ; count_frames = 0; count_pixels = 0
+    ; count_frames = 0; count_iters = 0
     lda #0
     sta count_frames
-    sta count_pixels
+    sta count_iters
+    sta count_iters + 1
 
-    ; total_ms = 0.0; total_pixels = 0.0
-    ldx #total_ms
-    jsr ZF1
-    ldx #total_pixels
-    jsr ZF1
+    ; total_sec = 0.0; total_iters = 0.0
+    jsr ZFR0
+    ldx #.lobyte(total_sec)
+    ldy #.hibyte(total_sec)
+    jsr FST0R
+    ldx #.lobyte(total_iters)
+    ldy #.hibyte(total_iters)
+    jsr FST0R
 
     jsr clear_screen
     jsr status_bar
+    jsr display_coords
 
     lda #0
     sta fill_level
@@ -1612,6 +1854,7 @@ not_skipped_mask:
     zoom_factor cx, sx, aspect_x
     add32 cx, cx, ox
     zoom_factor cy, sy, aspect_y
+    neg32 cy
     add32 cy, cy, oy
     jsr mandelbrot
     jsr pset
@@ -1623,38 +1866,32 @@ not_skipped_mask:
 
 no_key:
     ; check if we should update the counters
-    ;
-    ; count_pixels >= width? update!
-    inc count_pixels
-    lda count_pixels
-    cmp #width
-    bmi update_status
 
     ; count_frames >= 120? update!
     lda count_frames
     cmp #120 ; >= 2 seconds
-    bmi skipped
+    bpl update_status
+    jmp skipped
 
 update_status:
-    ; FR0 = (float)count_pixels & clear count_pixels
-    lda count_pixels
-    sta FR0
-    lda #0
-    sta FR0 + 1
-    sta count_pixels
+    ; FR0 = (float)count_iters & clear count_iters
+    copy16 FR0, count_iters
     jsr IFP
+    lda #0
+    sta count_iters
+    sta count_iters + 1
 
-    ; FR1 = total_pixels
-    ldx #.lobyte(total_pixels)
-    ldy #.hibyte(total_pixels)
+    ; FR1 = total_iters
+    ldx #.lobyte(total_iters)
+    ldy #.hibyte(total_iters)
     jsr FLD1R
 
     ; FR0 += FR1
     jsr FADD
 
-    ; total_pixels = FR0
-    ldx #.lobyte(total_pixels)
-    ldy #.hibyte(total_pixels)
+    ; total_iters = FR0
+    ldx #.lobyte(total_iters)
+    ldy #.hibyte(total_iters)
     jsr FST0R
 
 
@@ -1667,44 +1904,66 @@ update_status:
     sta count_frames
     jsr IFP
 
-    ; FR0 *= ms_per_frame
-    ldx #.lobyte(ms_per_frame)
-    ldy #.hibyte(ms_per_frame)
+    ; FR0 *= sec_per_frame
+    ldx #.lobyte(sec_per_frame)
+    ldy #.hibyte(sec_per_frame)
     jsr FLD1R
     jsr FMUL
 
-    ; FR0 += total_ms
-    ldx #total_ms
-    ldy #0
+    ; FR0 += total_sec
+    ldx #.lobyte(total_sec)
+    ldy #.hibyte(total_sec)
     jsr FLD1R
     jsr FADD
 
-    ; total_ms = FR0
-    ldx #total_ms
-    ldy #0
+    ; total_sec = FR0
+    ldx #.lobyte(total_sec)
+    ldy #.hibyte(total_sec)
     jsr FST0R
 
-    ; FR0 /= total_pixels
-    ldx #total_pixels
-    ldy #0
+    ; FR0 /= total_iters
+    ldx #.lobyte(total_iters)
+    ldy #.hibyte(total_iters)
     jsr FLD1R
     jsr FDIV
 
-    ; convert to ASCII in INBUFF
+    ; FR0 *= us_per_sec
+    ldx #.lobyte(us_per_sec)
+    ldy #.hibyte(us_per_sec)
+    jsr FLD1R
+    jsr FMUL
+
+    ; round (down) to integer
+    jsr FPI
+    clc
+    jsr IFP
+
+    lda #speed_start
+    sta text_col
+    lda #0
+    sta text_row
+    draw_string_const str_speed
+
+    lda text_col
+    pha
+    draw_string_const str_padding
+    pla
+    sta text_col
+
+    ; convert to ASCII in INBUFF and print
     jsr FASC
-
-    ; print the first 6 digits
-    draw_text_indirect speed_start, speed_precision, INBUFF
-    draw_text speed_start + speed_precision, str_speed_len, str_speed
-
+    jsr draw_string
 skipped:
 
+    ; sx += fill_level[fill_masks] + 1
+    ldx fill_level
+    lda fill_masks,x
     clc
-    lda sx
-    adc #1
+    adc #1 ; will never carry
+    adc sx
     sta sx
-    lda sx + 1
-    adc #0
+    lda #0
+    adc sx + 1
     sta sx + 1
 
     lda sx
@@ -1714,12 +1973,15 @@ skipped:
 
 loop_sx_done:
 
+    ; sy += fill_level[fill_masks] + 1
+    ldx fill_level
+    lda fill_masks,x
     clc
-    lda sy
-    adc #1
+    adc #1 ; will never carry
+    adc sy
     sta sy
-    lda sy + 1
-    adc #0
+    lda #0
+    adc sy + 1
     sta sy + 1
 
     lda sy
@@ -1738,7 +2000,13 @@ fill_loop_done:
 
 loop:
     ; finished
-    draw_text 40 - str_done_len, str_done_len, str_done
+
+    lda #(40 - str_done_len)
+    sta text_col
+    lda #0
+    sta text_row
+    draw_string_const str_done
+
     jsr keycheck
     beq loop
     jmp main_loop

readme.md

@@ -18,7 +18,7 @@ Enjoy! I'll probably work on this off and on for the next few weeks until I've g
 
 ## Current state
 
-Basic rendering is functional, with interactive zoom/pan (+/-/arrows) and 4 preset viewports via the number keys.
+Basic rendering is functional, with interactive zoom/pan (+/-/arrows) and 6 preset viewports via the number keys.
 
 The 16-bit signed integer multiplication takes two 16-bit inputs and emits one 32-bit output in the zero page, using the Atari OS ROM's floating point registers as workspaces. Inputs are clobbered.
 
@@ -27,7 +27,7 @@ The 16-bit signed integer multiplication takes two 16-bit inputs and emits one 3
 * when expanded RAM is available as on 130XE, a 64KB 8-bit multiplication table accelerates the remaining multiplications
 * without expanded RAM, a table of half-squares is used to implement the algorithm from https://everything2.com/title/Fast+6502+multiplication
 
-The mandelbrot calculations are done using 4.12-precision fixed point numbers with 8.24-precision intermediates. It may be possible to squish this down to 3.13/6.26.
+The mandelbrot calculations are done using 3.13-precision fixed point numbers with 6.26-precision intermediates.
 
 Iterations are capped at 255.
 

todo.md

@@ -1,19 +1,17 @@
 things to try:
 
-* skip add on the top-byte multiply in sqr8/mul8
-  * should save a few cycles, suggestion by jamey
+* fix status bar to show elapsed time, per-iter time, per-pixel iter count
+
+* 'turbo' mode disabling graphics in full or part
 
 * patch the entire expanded-ram imul8xe on top of imul8 to avoid the 3-cycle thunk penalty :D
 
-* try 3.13 fixed point instead of 4.12 for more precision
-  * can we get away without the extra bit?
-  * since exit compare space would be 6.26 i think so
+* maybe clean up the load/layout of the big mul table
+
+* consider alternate lookup tables in the top 16KB under ROM
 
 * y-axis mirror optimization
 
-* 'wide pixels' 2x and 4x for a fuller initial image in the tiered rendering
-  * maybe redo tiering to just 4x4, 2x2, 1x1?
-
 * extract viewport for display & re-input via keyboard
 
 * fujinet screenshot/viewport uploader