Technical questions about 3DO hardware (capabilities, etc.)

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Technical questions about 3DO hardware (capabilities, etc.)

Post by spiffyone » Wed May 30, 2012 8:37 pm

Just out of curiosity, since I've gone over the system FAQs and some of the hardware details. Note that I'm not a programmer or "techie" though I do have some rudimentary understanding of hardware, so these questions may seem silly to those more knowledgeable in such subjects.

Could the 32kb of SRAM, theoretically, be used as off chip storage/cache for the ARM CPU and math co-processor? In the FAQ it was noted that the SRAM cannot be written directly to by software, and must go through OS calls, so I'm guessing the OS didn't support such usage, but could it be possible to support using SRAM as external cache for the CPU and math co-processor if writing directly to the hardware (which, I understand, isn't possible...yet...or is it?) or if 3DO had ever issued an OS update supporting such usage?

I know an issue with 3DO's ARM and math co-processor as opposed to other systems of that gen was the lack of on chip cache. Surely, had 3DO allowed it, 32kb of SRAM, albeit external to the CPU, would've been useful on some level. It is apparently connected directly to the CPU/math co-processor by a 32bit bus.

Also, I've read that there were bus contention issues with the system, and that the CPU would be halted while the graphics/video processors did their thing/wrote to display. Is this true? If so, why?

Shouldn't the system DMA as well as the dual ported VRAM connected to the graphics/video processors alleviate at least some of that issue? Again, forgive my lack of knowledge/understanding of the subject, but it seems odd to me that the CPU would halt completely.

Finally, has anyone run tests to find out how many polys could be pushed? I know that 3DO used quads, like Saturn (but not exactly alike), so obviously the "tests" would not be exactly the same as a triangle renderer like PS1, etc., but does anyone have a ballpark?

I've read estimates ranging from 20k pps to 80k pps. I'm asking specifically in terms of maximum flat shaded quads/polys, as well as maximum fully textured quads/polys, both with no game code/AI, and, of course, estimates with game code. As a baseline, I guess the quads would be 32x32 or 16x16 (which size did Sega use in their Saturn estimates?).


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