🚀 go-pugleaf

In article (Mike (My Watch Has Windows) Meyer) writes:
>In article <925@boing.UUCP> dale@boing.UUCP (Dale Luck) writes:
>Hmm - there could be something in the Amiga to cause this to be true,
>but it isn't for Suns.
The only suns I know of with 16 bit buses are sun2's. The Amiga Blitter
is certainly faster than that. In X11 for the Amiga I can show that the
Amiga Blitter is just as fast as a 020@15mhz on a 32 bit bus by comparing
speeds of operations of a sun3/50 versus a STANDARD A2000.
>
>The blitter can make thing the blit happen as fast as memory can deal
>with it. All it takes for the 68020 to do that is for all the
>instructions to land in cache.

Are you implying that just because instructions land in the 020's cache
that they no longer take time to execute?  I believe all the cache does
is act as a fast memory with access time of 2 clock cycles instead of 3 or
more for outside memory.

 If the Amiga gives the blitter twice
>the memory bandwidth of the CPU, then the 68020 can't keep up on that
>hardware - it can't push things through memory fast enough. This will
>be different on the 3000, though.

I believe the 020 is still held to 4 clock cycles to
chip memory. If the memory access is 32 bits however, and the address
is on a 4 byte boundary then it can get 32 bits at once. So this does
even it out the speed differential a bit. This also means that it may
have less contention for the same chip memory as the blitter since the
blitter would have to do two memory accesses for every one of the 020.

-- 
Dale Luck     GfxBase/Boing, Inc.
{uunet!cbmvax|pyramid}!amiga!boing!dale