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PostPosted: Sun Jun 17, 2018 10:19 pm 
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Espozo wrote:
I thought I had shown in a picture that you can use BG3 for the middle layer in that scene in conjunction to a window layer, and you'd have enough color for everything but the rocky edge of the BG layer and a few highlights on the tree trunks that you could use a few 16x16 sprites for.

I don't remember that, but it's been a while. I guess that's sorted, then, except for the wooden structure. I wonder if that would be a good candidate for OBSEL switching?

Man, there's really almost nothing happening once that wooden structure comes down. Couple of tanks, couple of soldiers, couple of POWs, then the boss. Also water. Water everywhere.

I wonder how effective the half-overwrite trick would be. It's kinda like 2bpp, but with per-pixel palette granularity, and you can overlap palettes. The far waterfall in particular looks like it might be well set up for it, but it's hard to know without trying...

Why does this video have such slow water? I actually went and looked up footage of somebody playing real hardware, hoping we got it wrong, but the water is fast on real hardware. This honestly looks better in some ways...

lidnariq wrote:
It's not clear whether that difference is big enough to matter.

If you're getting slowdown, it's almost certainly big enough to matter. And with Metal Slug you're probably getting slowdown. Whether it matters enough to justify the extra cartridge cost is another question. (With a modern MS port, I'd say yes, because the purpose is to test the limits of the console rather than to make money, and the market expectations of potential buyers, if any, are much more flexible. Even back in the day, shogi players were apparently willing to put up with a lot...)

For my game, the big reason for using fast SRAM would be to speed up my monster raster effect, as I said. Just the faster interrupt servicing and the elimination of the trampoline account for something like 15% more compute time for the main game loop. Whether I'll need it or not remains to be seen; most of the heavy lifting in my game is done by the GSU...

lidnariq wrote:
decoding both $3xxx and $5xxx should have required another pin on the MAD-1

Would it be any simpler to map SRAM to $2000-$3FFF and just ignore $21xx? (I'm guessing not, unless the CPU simply doesn't put $21xx accesses on the A bus at all.) How expensive would a custom address translator be?


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PostPosted: Mon Jun 18, 2018 12:35 am 
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Formerly Espozo
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Location: Nacogdoches, Texas
93143 wrote:
Why does this video have such slow water? I actually went and looked up footage of somebody playing real hardware, hoping we got it wrong, but the water is fast on real hardware. This honestly looks better in some ways...

The Neo Geo video hardware has a custom feature where it can automatically increment the graphics address for each 16x16 sprite block every frame until it reaches a defined point, and then starts over. That's why all the water operates at 60fps (even if, artistically, it really doesn't need to...).


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PostPosted: Mon Jun 18, 2018 1:42 am 
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93143 wrote:
Would it be any simpler to map SRAM to $2000-$3FFF and just ignore $21xx?
Nope. The only simple option is a 4K window, by decoding all of A12...A15.
Quote:
(I'm guessing not, unless the CPU simply doesn't put $21xx accesses on the A bus at all.)
When the S-CPU is accessing $21xx, both the A bus and PA bus have the same bottom 8 bits. If a cart device mapped something into $21xx according to the A bus (instead of a PA bus) the distinction would only be visible when trying to DMA to/from it. (It wouldn't work very well)

Edit: you might be able to do some cleverness with decoding $2000-$3FFF and /PARD ? Might have a problem with race conditions, though.

Quote:
How expensive would a custom address translator be?
Not bad. ROM-as-logic: SST39SF010 86¢/@26. GAL: ATF16V8 78¢/@26. GreenPak: 50¢/@100. Discretes: 74'1g86 + 74'138 21¢/@10 + 29¢@10


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