diff --git a/mandel.s b/mandel.s
index ff402ad..06d59e7 100644
--- a/mandel.s
+++ b/mandel.s
@@ -13,16 +13,20 @@ zy_2  = $92     ; fixed4.12: z_y^2
 zx_zy = $94     ; fixed4.12: z_x * z_y
 dist  = $96     ; fixed4.12: z_x^2 + z_y^2
 
-iter  = $a0     ; u8: iteration count
-zoom  = $a1     ; u8: zoom shift level
-temp  = $a2     ; u16
-temp2 = $a4     ; u16
+frames       = $a0 ; u16
+frames_total = $a2 ; float48; total frames
+pixels       = $a8 ; u16
+pixels_total = $aa ; float48; total pixels
+
+iter         = $b0 ; u8: iteration count
+zoom         = $b1 ; u8: zoom shift level
+temp         = $b2 ; u16
+pixel_ptr    = $b4 ; u16
+pixel_color  = $b6 ; u8
+pixel_mask   = $b7 ; u8
+pixel_shift  = $b8 ; u8
+pixel_offset = $b9 ; u8
 
-pixel_ptr    = $b0 ; u16
-pixel_color  = $b2 ; u8
-pixel_mask   = $b3 ; u8
-pixel_shift  = $b4 ; u8
-pixel_offset = $b5 ; u8
 
 ; FP registers in zero page
 FR0 = $d4
@@ -51,6 +55,10 @@ DLISTH = $D403
 SDLSTL = $230
 SDLSTH = $231
 
+; interrupt stuff
+XITVBV = $E462
+SETVBV = $E45C
+
 .data
 
 strings:
@@ -216,6 +224,10 @@ color_map:
     copy 4, dest, arg
 .endmacro
 
+.macro copyfloat dest, arg
+    copy 6, dest, arg
+.endmacro
+
 ; 2 + 8 * byte cycles
 .macro neg bytes, arg
     sec ; 2 cyc
@@ -613,6 +625,24 @@ loop:
 done:
 .endmacro
 
+.proc vsync_handler
+    inc frames
+    bne no_carry
+    inc frames + 1
+no_carry:
+    jmp XITVBV
+.endproc
+
+.proc update_speed
+    ; convert frames (u16) to fp
+    ; add to frames_total
+    ; convert pixels (u16) to fp
+    ; add to pixels_total
+    ; (frames_total * 16.66666667) / pixels_total
+    ; convert to ATASCII
+    ; draw text
+.endproc
+
 .proc start
 
     ; ox = 0; oy = 0; zoom = 0
@@ -675,6 +705,12 @@ copy_byte_loop:
     lda #$22
     sta DMACTL
 
+    ; install the vblank handler
+    lda #7 ; deferred
+    ldx #.hibyte(vblank_handler)
+    ldy #.lobyte(vblank_handler)
+    jsr SETVBV
+
 main_loop:
     ; sy = -92 .. 91
     lda #(256-half_height)