Is my understanding correct? (Jaguar chip setup)

[+CyranoJ]

And making a loopback statements disregarding ChillyWillies testimony of his own substantial experience coding using the Jag and similar setups instead of asking him why he supposed maybe he got different results than Typo's tests for 2D stuff is perhaps a little rude?

 

Not really. 'Better use' is very subjective.

 

For instance, I'd rather have one nicely drawn sprite, than have the blitter draw 1000 utterly shit ones. Like we've said all along, its the game that counts, not how it's coded.

 

Going by 'not making the best use of the hardware' all the 2600 Batari Basic games must be shit..... *sigh*

Edited April 6, 2013 by CyranoJ

[JagChris]

Not really. 'Better use' is very subjective.

 

For instance, I'd rather have one nicely drawn sprite, than have the blitter draw 1000 utterly shit ones. Like we've said all along, its the game that counts, not how it's coded.

 

Going by 'not making the best use of the hardware' all the 2600 Batari Basic games must be shit..... *sigh*

 

He's not talking about subjective terms. He's talking about actual performance levels in his experience of when the 68k gets in the way.

And the sprites he's used in his port of Wolf3d look pretty good.

[JagChris]

Going by 'not making the best use of the hardware' all the 2600 Batari Basic games must be shit..... *sigh*

 

And no one implied anything of the sort.

[+CyranoJ]

ChillyWillies testimony of his own substantial experience coding using the Jag

That's one thing I found really helped 32X games

 

Umm yeah.. There is no doubt that turning the 68000 off would give you a substantial speed boost if the other risc chips had more ram and were not bugged to all hell but they don't have more ram, and they are bugged to all hell.... And attempting to code an entire game on the GPU is so far beyond pointless it's not worth doing, unless you want something really simplistic like 'Surrounded' or 'I'm thinking of a number'

[JagChris]

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Umm yeah.. There is no doubt that turning the 68000 off would give you a substantial speed boost if the other risc chips had more ram and were not bugged to all hell but they don't have more ram, and they are bugged to all hell.... And attempting to code an entire game on the GPU is so far beyond pointless it's not worth doing, unless you want something really simplistic like 'Surrounded' or 'I'm thinking of a number'

 

lol. good morning sunshine. Don't forget to smile sometime today.

[+Gemintronic]

I've heard about the UART problems but not the RISC errata. How documented is that stuff? Could we get it to the point where using RISC would be safe?

[+DrTypo]

I haven't written code for the DSP so I can't comment much about it. However it is extremly similar to the GPU. From what I've read, it has a problem with memory access that you don't have with the GPU. The workaround seems easy though.

 

The GPU is mostly safe to use. It has a few pipelining issues that you need to be aware of. But these are not very common situations and the workaround is easy.

The main problem is the lack of local RAM.

If your code doesn't fit the 4K then you're in trouble. You can either cut your code in 4K chunks or use the "GPU in main" technique. Both solutions are a bit of a PITA to implement and have their own performance issues.

 

Using the 68K doesn't cut GPU/Blitter performance in half. Yeah, if the 68K runs from interrupt then it can be pretty bad since then it has priority over GPU and Blitter. Don't run large 68K routine under interrput! It's evil!!!!!!!1!1!1!1!

No the problem is that if you give too much work to the 68K. "Too much work" means it takes more time for the 68K to do its stuff that it takes to the GPU/Blitter to do the rendering. Then you've to consider moving code to the GPU. And you're going to hit the 4K limit. And you're going to cry :'(

 

For complex rendering routine (DOOM for example), you hit the 4K limit with just the rendering code alone. We're not even talking about gameplay code. This kind of situation can make you cry a lot. :''''(((

[Chilly Willy]

Certainly, turning off the 68000 isn't something to be done in general, but there are cases where it would be helpful. It's just another tool for the developer when designing how the game works. To say NEVER do it is just as bad as to say ALWAYS do it.

 

Anywho, Doom is rather interesting - the rendering is split into stages, each one triggering the next. After a few stages, the variables in ram aren't needed anymore, so the 68000 is allowed to continue running the game logic in parallel to the later stages of the GPU code finishing the rendering. Once you're down to columns and spans (the two graphical operations done in Doom rendering), the GPU starts sending operations to the BLITTER. Funny enough, the 68000 handles all the OP setup for each frame after the GPU finishes the last stage. Having the GPU load later stages of code to work on a problem is very similar to how the RSP works in the N64 - since there is only 4KB of instruction ram in the RSP, the "microcode" is split into sections which are loaded into instruction ram as needed. Given how efficient loading the GPU local ram is, having GPU code load itself in stages could have easily been used by more games than just Doom. It probably would have become standard if the Jag had lasted in the marketplace.

[+CyranoJ]

 

lol. good morning sunshine. Don't forget to smile sometime today.

 

Your insights and generalizations make me smile all the time.

[+CyranoJ]

I've heard about the UART problems but not the RISC errata. How documented is that stuff? Could we get it to the point where using RISC would be safe?

 

Safe, yes.

practical, no.

[JagChris]

Your insights and generalizations make me smile all the time.

 

As do yours

[+CyranoJ]

As do yours

 

At least we're on the same page. I just want to see more stuff for the Jaguar, and I don't particularly care how it's made, how efficient it is, or what it's written in. As long as the homebrew keeps flowing and its fun to play, that's all that counts.

[Chilly Willy]

As long as the homebrew keeps flowing and its fun to play, that's all that counts.

 

In the end, that's all that matters, but here in the programming forum, we devs love to get into little spats over those parts that don't matter to anyone else.

[+CyranoJ]

In the end, that's all that matters, but here in the programming forum, we devs love to get into little spats over those parts that don't matter to anyone else.

 

However, it's when the non-devs start spouting utter crap based on nothing... that's when it gets irritating

[JagChris]

However, it's when the non-devs start spouting utter crap based on nothing... that's when it gets irritating

 

Why you gotta pour hatorade on our bromance G?

[JagChris]