update loop:
  HIRES:  85 + 14.1875C + 364.5D
  ELSE :  85 + 14.1875C + 316.5D


                    NOROTATE/NOFLICKER         ROTATE/NOFLICKER
load spec               555 / +9                 915 / +9
load hires              474 / +9                 834 / +9
load hiclr              914 / +23               1333 / +23

(x)or spec              653 / +9                1069 / +9
(x)or hires             572 / +9                 988 / +9
(x)or hiclr            1012 / +23               1485 / +23

mask spec               747 / +9                1629 / +9
mask hires              666 / +9                1523 / +9
mask hiclr             1100 / +23               2017 / +23

C = number chars = 32*24
D = num dirty areas, max(C/8)
N = num chars needing update
S = num dirty chars with sprites
L = num dirty chars with sprite with 1st char load or SCROLLER mode


SPECTRUM:

85 + 14.1875C + 316.5D
+ 393N + (32N NOFLICKER)
+ 152S + (202S NOFLICKER)
- 210L
+ sprites


HIRES:

85 + 14.1875C + 364.5D
+ 320N + (32N NOFLICKER)
+ 205S + (202S NOFLICKER)
- 210L
+ sprites


HICLR:

85 + 14.1875C + 316.5D
+ 526N + (32N NOFLICKER)
+ 4S + (398S NOFLICKER)
- 206L
+ sprites