Espozo wrote:
AWJ wrote:
Sprite drawing on the SNES is fundamentally limited by VRAM bandwidth.
So really, "34 8x8 slivers" doesn't matter in the PPU's eyes, only 272 sprite pixels.
What I've been calling a "sliver" is an 8x1 pixel area, not 8x8. The limit is 272 sprite pixels, but I express it as 34 8-pixel slivers to emphasize that even transparent pixels count.
Espozo wrote:
So what you're saying is that with the SNES, it devotes half of the time (hblank) to generating sprites, and the other half (active display) generating BGs
Pretty much, except horizontal blanking is approximately one-fourth of time.
Espozo wrote:
but on these arcade systems, both hblank and active display are spent on both BGs and sprites, it's just that there are more busses? I almost wonder as to how it could have been so expensive just to add one bus in many situations like this.
That's what it sounds like. One problem with adding a bus to a console or widening one is that the additional traces make the motherboard bigger. Back then, video game consoles came from Japan, and with its population packed into tiny apartments in big cities, Japan wasn't a big fan of consoles with
XBOX HUEG cases. You have to count not only the price of the console but also the price of the real estate it occupies. That's one reason why Japan liked the PC Engine: not much bigger than a Discman CD player. It's also why so many consoles since 2000 can stand on end.
Espozo wrote:
Also though, because many arcade machines use chr rom, I imagine the bandwidth is higher than something like vram on the SNES?
Not necessarily. As far as I can tell, the SRAM and mask ROM available in 1990 were about the same speed.
Espozo wrote:
I wonder how far you could have gotten with the SNES's video hardware if you only made a few minimalistic changes to it.
I can think of one optimization that could have increased overdraw: let a program completely disable certain layers in favor of handing those VRAM cycles over to the sprite processor. But once you add enough of these optimizations, you've essentially reinvented the Game Boy Advance PPU.