1284P addon

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martinsustek
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Re: 1284P addon

Post by martinsustek »

D3thAdd3r wrote:I agree with 95% your analysis ;)
martinsustek wrote:Count of sprites in mode 3 is limited by RAM size (number of ramtiles), so double RAM means double sprites per screen (in fact more than double, because sprites are not whole RAM).
The count has always been just about equally limited by time also, now actually it's more time limited. With the newest kernel upgrade, I think most games can have more ram tiles than they can even use.
You're right, I forgot, that it takes kernel time to prepare ramtiles. But new kernel will have more time because of sound mixing during scanline, am I right? Maybe there will be some other possible speed enhancements when we will have more RAM. How many instructions is needed to process one sprite? Is it possible to fit part (one line?) of sprite processing to black part of scanline (even in case of few tiles narrower image and added border - I like how border on ZX Spectrum looked like)?
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mapes
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Re: 1284P addon

Post by mapes »

D3thAdd3r wrote:I agree with 95% your analysis ;)
martinsustek wrote:Count of sprites in mode 3 is limited by RAM size (number of ramtiles), so double RAM means double sprites per screen (in fact more than double, because sprites are not whole RAM).
The count has always been just about equally limited by time also, now actually it's more time limited. With the newest kernel upgrade, I think most games can have more ram tiles than they can even use. Without any code running for a game engine, just the time it takes to ProcessSprites() and blit ram tiles, would limit us to much less than double that of say newest MegaBomber version(37 ram tiles with 30x24 vram, quite short screen..). We can probably max out time for 28mhz on the 644 right now, before we run out of actual ram(at least for a simple test!) Now I'm not against the 1284 idea, flash would improve games greatly, but I think a lot of people would be disappointed that our sprite capabilities would not increase much(it wouldn't feel like that much of an upgrade for the hardware change). I will do a test, without sound, default vram height and see what the max possible is for our clock speed and one for 30x22 vram(about the minimum useful height for say a big sprite fighter game). To go further(reach maximum blits every frame) Kernel would need redesigns and existing games reprogrammed to run on opposite ticks from blits, game logic one tick, sprite blit next tick(max possible vblank time for blits). I'm experimenting with just that and it does make a big difference!
D3thAdd3r, I'm very interested in your attempts at trying to determine the max number of sprites achievable. Although for a game, I'd obviously want sound, but I'm still very interested to see what can be pulled off. Also, which the sound engine being more on the fly (vice the buffer), how would sound being disabled impact your proposed plan? I wouldn't think we would want to blit sprites in the middle of a frame (please be aware, I am not an experienced programmer or super hardware buff)

-Mapes
Last edited by mapes on Thu Jan 19, 2012 6:31 pm, edited 1 time in total.
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D3thAdd3r
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Re: 1284P addon

Post by D3thAdd3r »

Most likely it will end up a simple little program where you can place sprites wherever you want and a waste cycle loop you can increase cycles until it crashes. With tile based counters for number ram tiles, cycles, first draw line, etc and the ability to switch sprite blitting to my somewhat slow compressed routines. Probably helpful to see what can be pulled off under different circumstances in the planning stages of a game.
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kscharf
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Re: 1284P addon

Post by kscharf »

I'd like to see the schematic for the adapter too.
BTW the atmega1284P isn't 100% compatible with the '644P, it's a superset in that it has a SECOND 16 bit timer counter unit. This is burried in the data sheets since Atmel has TWO different data sheets for the device. One covers ONLY the atmega1284P, the other covers the 16,32,64, and 128k devices. Confusing!

Another thing, I know the xmega port is now dead, but I've heard of xmegas being overclocked to as high as 50mhz with good results. (some have claimed as high as 80mhz, but that might be on selected devices).
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DaveyPocket
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Re: 1284P addon

Post by DaveyPocket »

Sorry guys I've been flooded with work lately. I'll get a (hopefully readable) schematic shortly, I totally forgot about this.

I was never aware of that second timer... Could this be the reason we have trouble overclocking? :?
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