oompa loompa
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Post by oompa loompa on Sept 3, 2012 20:38:16 GMT -5
I'm programming for the SNES right now.... Wow, this is a tough console to code on . 65816 seems so "budgetary" compared to the selection of CPU choices in 1990. *cough*cough* takes 5 instructions for me to increment or decrement the stack pointer an arbitrary amount. I thought 65816 was top of the line ? Anyone know why Nintendo chose 65816? Oh, not to mention that it's next to impossible to write to VRAM during h-blank. And if someone dares to write to VRAM during active display, their data won't ever be processed by the PPU, wish they spent a few extra transistors on a FIFO ^_^ I like that instruction cycle times are much more optimized on 65816 though. And I admit, I like the DMA features.
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Post by Deleted on Sept 4, 2012 8:26:18 GMT -5
I thought the 65816 was similar in architecture to the 6502? I always assumed that Nintendo chose that processor so that developers wouldn't have a huge learning curve from the NES days.
I remember reading up on SNES development close to 2 years ago, and it just looked like a royal pain in the rear. Kudos to you if you manage to get a decent compiler written. Shiru has done some SNES games (he did the 16 bit XMAS cart that retrozone sold, and he just released a Donkey Kong remake, called Classic Kong). He might be a person to talk to for any issues if you run into them.
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Post by Deleted on Sept 4, 2012 10:23:54 GMT -5
Anyone know why Nintendo chose 65816? Nintendo intended to have the DSP-1 as co-processor alongside the 65816, but it got removed at the last minute ( probably because of budgetary reasons ). Even though that doesn't explain the choice of the 65816 per se, it would have unloaded most of the math related instructions to the DSP-1 making the choice of a not-so-high-end main CPU less unwieldy.
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Post by sega16 on Sept 4, 2012 15:24:56 GMT -5
To me it sounds like nintendo was just being cheap. They wanted to keep cost down.
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
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Post by oompa loompa on Sept 4, 2012 16:49:22 GMT -5
On the bright side, 65816 is really fast. At 4MHz, it accomplishes more than the 68k at 8MHz. If using the 65816 to program directly in assembly, then the system can be really pushed to the limits. If programming in a higer language, then it's hell , unless the compiler is optimizing the instructions. And then during the SNES era, a lot of other consoles were using custom ASICs and custom co-processors (I'm referring to the Jaguar ). So I guess it also adds to the sophistication and cost to add fancy things.
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Post by Deleted on Sept 4, 2012 17:45:58 GMT -5
Well, Oompa, it looks like you have your work cut out for you! Optimize the hell out of BasiegaSNESxorz
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Post by sega16 on Sept 4, 2012 18:45:11 GMT -5
On the bright side, 65816 is really fast. At 4MHz, it accomplishes more than the 68k at 8MHz. So it sounds like blast processing was a lie.
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Post by Deleted on Sept 4, 2012 19:35:45 GMT -5
So it sounds like blast processing was a lie. In allot of real-world circumstances the Megadrive will actually outperform the SNES.
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Post by sega16 on Sept 4, 2012 19:46:02 GMT -5
And don't forget that the sega genesis has good fast DMA that works on active display.
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Post by Deleted on Sept 4, 2012 21:49:41 GMT -5
"Blast Processing" was a marketing scheme that basically meant "the M68K is faster than the SNES's CPU, but we have to use a cool term", and it worked for a while. The Genesis does perform faster (look at a lot of the speedy games for the system that SNES couldn't match or beat), however, the SNES has a lot more going for it than the Genesis, such as native opacity, 4 bg layers (I believe), more palettes and colors per palettes, and an orchestrated sound chip as opposed to an FM. However, the Genesis was HIGHLY under utilized, IMO anyway.
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
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Post by oompa loompa on Sept 4, 2012 23:24:08 GMT -5
And don't forget that the sega genesis has good fast DMA that works on active display. Yes!! This is the win right there Oh, and for BASIC, if you change VRAM (like PRINT statement), the code waits for VBLANK. Unlike the Genesis, it just goes and writes, even though the CPU could be halted. But still, Genesis doesn't throw away the data. I don't think this is a big deal I think - on real games written in asm or C, the developer would know better "Blast Processing" was a marketing scheme that basically meant "the M68K is faster than the SNES's CPU, but we have to use a cool term", and it worked for a while. The Genesis does perform faster (look at a lot of the speedy games for the system that SNES couldn't match or beat), however, the SNES has a lot more going for it than the Genesis, such as native opacity, 4 bg layers (I believe), more palettes and colors per palettes, and an orchestrated sound chip as opposed to an FM. However, the Genesis was HIGHLY under utilized, IMO anyway. Yes, 68K would win, in terms of CPU performance. Genesis / 68K instruction set is very flexible, has many registers, and Genesis DMA is faster. 65816 can execute more instructions then the Genesis, but these instructions are pretty clear cut, hardly any flexibility. The flexibility I see is in accessing the memory - either access the Zero Page, Absolute Address, Indirect from everywhere, etc etc. But then these fancy addressing modes take up more cycles as well I dunno actually... unless nobody has pushed the SNES to its limits yet ? Wolf3D is on SNES
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Post by Deleted on Sept 5, 2012 4:13:34 GMT -5
Wolf3D is on SNES Apart from the fact that it's pretty much the most lightweight "3D" game you can make, the SNES version runs at a abysmal low resolution ( which is scaled up using Mode7 ). Here's a comparison between the native resolution of Wolfenstein on SNES and the default Megadrive resolution
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Post by Deleted on Sept 5, 2012 6:38:22 GMT -5
Ha, that's interested moon. What about Doom on SNES? Same thing, I'd imagine, right, since both use the same (similar?) engine?
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Post by Deleted on Sept 5, 2012 7:24:02 GMT -5
What about Doom on SNES? Same thing, I'd imagine, right, since both use the same (similar?) engine? Not exactly, Doom uses the Super FX 2 ( GSU-2 ) chip ( the big square chip in the middle ) .. wouldn't have been possible without. Also, rendering appears to be done at a resolution of 108x144 ( compared to the 112x80 of Wolfenstein ), so it's only being stretched horizontally.
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Post by Deleted on Sept 5, 2012 7:42:51 GMT -5
Neat. I never cared too much for the consolized versions of these 2 titles, but it's interesting to see the limitations of them.
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