🚀 go-pugleaf

In article <30974@ut-emx.UUCP> (Jonathan Abbey) writes:
>I'd like some hard data on the blitter vs. the CPU for polygon rendering..
>I've heard people here assert that the CPU is faster, even on a 68000.

The definitive answer to this was given by Jeremy Sans (wrote StarGlider)
at the S.F. DevCon last year. His assesment was that the blitter and the
CPU were about equal. Where they varied was in the effort it took to set
up the "blit" versus the speed at which the blit was accomplished. The 
blitter is faster than the 68000 once it gets going but the 68000 could
set up for the next blit a lot faster than the blitter could. 68020 and
above processors won on both counts, mostly because of the instruction
cache/clock speed issues. So his analysis was that one's rendering function
had to be smart enough to "know" if the blit was larger than the cutoff
point for the processor and if so feed it to the blitter. The primary
advantage of the blitter was being able to calculate new data simultaneously
with the CPU while the blit is going on, although to make this truely
effective you have to make sure that the CPU doesn't go to the "Chip"
bus and that means True Fast Ram, and no interrupts (because fetching
the interrupt vector requires talking to chip ram.)


--
--Chuck McManis						    Sun Microsystems
uucp: {anywhere}!sun!cmcmanis   BIX: <none>   Internet: cmcmanis@Eng.Sun.COM
These opinions are my own and no one elses, but you knew that didn't you.
"I tell you this parrot is bleeding deceased!"