Alto Hardware Manual Section
3:
Emulator
25
XMLDA
XMSTA
TIMING
DETAILS
The microcode has roughly the following speed characteristics:
Horizontally, along one raster line
(so to speak):
store constant
move block
if
skew
not
zero
if
source not zero
1st or last word
function not store
13
cycles/word
23
cycles/word
add 6
add 7
add
13
add 6.
Vertical loop overhead (time to change· raster lines):
14-21
cycles/scanline, depending on source/dest alignment
add 6
if
function uses gray
Initial setup overhead (time to start or resume from interrupt):
approximately
240
cycles
Total for a typical character, 8 wide by 14 high:
approximately
1500
cycles
These timings all in units
of
Alto microinstruction cycles
and,
do
include all memory wait time
and
do
not include any degradation
due
to competing tasks,
such
as
the display
or
disk.
For
typical characters on the Alto screen,
BITBLT
is
about
2/3
the speed
of
CONVERT.
61025B
Extended Memory Load Accumulator (Alto
II
only)
Loads
ACO
from the location addressed
by
ACI
in the alternate bank.'
61026B
Extended Memory Store Accumulator (Alto
II
only)
Stores
ACO
into the location addressed by Acl
in
the alternate bank.
If
the the addressed
bank
of
memory has not been installed, the instruction yields undefined results
and
will probably
cause a .parity error. See section 2.3.
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