SpritesMind.Net

Hi you all.
With the SuperVDP project, I had a problem about speed, performance. Actually, how much tile can the 32X actually displays. Taking it back, I intend to benchmark the CPU, here's my method.

Enable VInt : Main loop : VInt routine : And I got R9 = $1 767D = 95 869 in NTSC,
or R9 = $1 BD5D = 114 013 in PAL.
Does it mean each CPU can do no more than ~100k operations by frame ?
On real hardware, it would be even slower since the operation I use (add #1,R8) just stays in 3 stages whereas more complex ones (mov.b @R8,R9 for example) uses 4 or even 5 stages !

when you benchmark PAL, is it in 240 or 224 lines? (or does it not matter?) just curious..

It doesn't matter if you use 224 or 240 lines, least not on MD on its own.

Line number doesn't matter. What's important is the refresh rate : 60Hz or 50Hz.

ob1 wrote:Does it mean each CPU can do no more than ~100k operations by frame ?

Did you count branch? In code with loop with add 1 (i.e. increment) and branch, result in counter ~100K means you have ~200K operations executed.

One SH2 @23MHz has performance approx 20 MIPS - 20000000 simple operations (usually register-register transfers) per second, so per frame you must get 333333..400000 (60/50Hz) simple operations.

I seem to remember that branches are relatively expensive on the SH-2 even with the delay slot instruction. Still, 95,869 * 60 fps * 2 instructions = 11.5 MIPS which means an average of ~2 cycles per instruction. You can do better than that if you keep your branching to a minimum and avoid pipeline stalls. Of course, on real world code you also have the cache to worry about too.