OC.TREI@CU20B.COLUMBIA.EDU (03/27/86)
From: Peter G. Trei <OC.TREI@CU20B.COLUMBIA.EDU>
While waiting for my official Commodore doc kit to arrive, I
borrowed a friend's hardware manual and started reading about the
blitter. It seems like a wonderful chip, and I conceived an
application which makes EXTREMELY heavy use of it. Which leads to my
question:
Just how fast is the blitter? How many clock cycles per processed
word? How do the number of inputs, the presence of an output, and the
use of modulos and/or barrel shifts effect the speed? I cant find
anything to pin this down in the Hardware manual with any accuracy. My
estimates range from 7 million words/sec (This is the clock speed.
After all, this is a pipelined device) to a mere 62,500 words/sec (in
line with a claim that it can lay down lines at 'over 1 M pixels/sec').
I guess I'll find out when I write the program, but I really think
this sort of nitty-gritty stuff should be in the hardware manual. If
it is in one of the volumes I have not obtained yet, I would
appreciate a pointer. If it is not in the docs, I hope CBN will post
the data here and put it in the next edition. I'd really like to pin down
the speed with better accuracy than a >100x range.
'Inquiring minds want to know!'
Peter Trei
oc.trei@cu20b
-------dale@amiga.UUCP (Dale Luck) (04/01/86)
In article <1651@caip.RUTGERS.EDU> OC.TREI@CU20B.COLUMBIA.EDU writes: > > Just how fast is the blitter? How many clock cycles per processed >word? How do the number of inputs, the presence of an output, and the >use of modulos and/or barrel shifts effect the speed? The actual measured speed of the blitter depends on how heavy the memory buss is already being used. Assuming no bitplanes/sprites/copper the blitter has nearly 100% access to the buss. With 100% access the blitter can read/write without any delay. The it can move data from one point to another is about 1.8M(words)/second. modulos do not affect timing. barrel shifting will drop the max bandwidth to 1.3M(words/sec). Each transfer is read and a write to the memory. These estimates are based on a single source and a single destination. Dale Luck horizontal lines can be drawn at a max rate of 28Mpixels/sec (b/w).
ekijak@ARDC.ARPA (04/12/86)
From: "Edmund S. Kijak" (POINT) <ekijak@ARDC.ARPA> What does a blitter do? What is a barrel shift? Why would modulos (modulo arithmetic ?) be of concern in graphics?