lee@sed170.HAC.COM (John Lee ) (07/22/89)
In article <26461@agate.BERKELEY.EDU> mwm@eris.berkeley.edu (Mike (I'll think of something yet) Meyer) writes: >In article <116365@sun.Eng.Sun.COM> raz@sun.UUCP (Steve -Raz- Berry) writes: [...] >You're right, the blitter does that. On the other hand, the 68010 may >be able to do it faster. The difference will be small. Except that the >Amiga has dual-ported memory, so the CPU can be doing usefull things ^^^^^^^^^^^^^^^^^^ >while the blitter is doing the block op. On '0[123]0 systems without >dual-ported memory, a blitter is a waste as far as speed is concerned. [...] > <mike >-- >So this is where the future lies Mike Meyer >In a beer gut belly; In an open fly mwm@berkeley.edu >Brilcreamed, acrylic, mindless boys ucbvax!mwm >Punching, kicking, making noise mwm@ucbjade.BITNET It does? I thought that the reason that the 5-6 bitplane low-res and 3-4 bitplane hi-res display modes, and blitter/copper operation slowed down the CPU in chip memory was due to the lack of dual ported memory and lack of a separate dedicated video bus. Dual-ported memory is mighty expensive and I don't think that the chip memory chips (4464's? I think?) are dual-ported. Also, I doubt that "on '0[123]0 systems without dual-ported memory, a blitter is a waste as far as speed is concerned." With fast-ram, both the CPU and blitter can go full-bore without contention, doubling effective memory operation rates. Even when the CPU must operate in chip-ram, the blitter will not take all available CPU/blitter DMA slots if it is not performing operations using all three ABC sources and the D destination, thus effective memory- operation rates are still higher than with the CPU alone (although not doubled). Now if the blitter were only used to do straight memory copying without shifting, masking or logic operations (i.e., A to D, no shifting or masking) and the same function could be done on a 3-instruction loop on the '010, or within the instruction cache on the '020 and '030, and no other operation could be done by the CPU simultaneously, THEN the blitter is indeed a waste of speed in chip-ram since the '0[123]0 could conceivably do the operation even faster than the blitter. ---John Lee ------------------------------------------------------------------------------- Raining CATS and DOGS? Join the RATS: Remote Amiga Teleconferencing System +--------+ John Lee | HUGHES | +--------+ ARPAnet: jhlee@hac2arpa.hac.com Hughes Aircraft Company The above opinions are those of the user and not of those of this machine.