PPC/68060 Faster or not?

[Phantom206]

So, it's faster to have an Amiga witch runs simultaneously an 604PPC with 68060 processor or not?

[bloodline]

Phantom206 wrote:
So, it's faster to have an Amiga witch runs simultaneously an 604PPC with 68060 processor or not?

Simple answer:

Is it faster to have a one engine or two?

[downix]

@Phantom206

You can't run both the 68060 and PPC simultaeously.  When one goes on, the other goes off.

[KennyR]

That's not strictly true, downix - you can have both processors running code from cache and only halt one to fetch more instructions for the other. The amiga RC5 client works like this, cracking with both PPC and 68k simultaneously.

For all other stuff you're right though. They have to be swapped constantly, flushing the cache each time. Not good.

[bloodline]

downix wrote:
@Phantom206

You can't run both the 68060 and PPC simultaeously.  When one goes on, the other goes off.

That's not right... they can't access the RAM at the same time but they can run at the same time, since they both have caches...

[Jose]

If you're considering the usage the current AmigaOS, wich is written in 68k code for the 68k processor,  then the answer is yes. But the degree to wich speed is afected depends much on the application. If you're runing only Classic applications then yes of course, because they 're using the 68k processor, and you'll put a faster one there (060). When it concerns PPC code (programs) things get more complicated cause the AmigaOS is still written in 68k code (PPC version coming). In that case, when PPC code is used it all dpends on if the relative amount of calls to the OS. With every call to the OS the computer switches from the PPC processor on wich it was executing the PPC code, to the 68k one to execute the OS  function. These switches take very long and harm speed very much, but only on programs that make many OS calls.
Of course when AmigaOS is rewritten for PPC, or if you use a replacement like MOS (different PPC OS but that runs  Classic (68k) applications),  these switch problems won't happen cause everything will run on PPC, wich can emulate a 68k processor faster than the real thing.

[Karlos]

@Jose

Programming efficient code for existing 680x0+PPC cards is quite interesting :-)

You can do a lot of os calls if you are careful - Design the code such that OS calls can be gathered together, create a 680x0 function that handles these OS calls and do a manual context switch to that function.

As an example I wrote a small test context in C that maintains a double buffered screen and handles input. I wrote it in vbcc-wos/68k to test the idea of manual switches on performance.

When I refresh, a 68K function is called. This function does the buffer flip and gathers and processes all the pending idcmp messages since the last frame (well up to a certian amount) into a pair of mouse / key data buffers. This included stuff like KeyMap based raw key mapping. So there were quite a few OS calls there.

The code then switches back to PPC and the input buffers are processed by PPC callback functions before the refresh() function finally returns.

So for the price of 2 complete context switches (PPC->68K->PPC) we get our buffer flipped, synchronised and the input ready to use by the PPC.

Hmm, I have wandered off topic again, havent I? Sorry, must be the late hour :-)
It worked quite well :-)

[lempkee]

ok, a small example of how it was for me... and many others.


blizzard ppc 040 25/240 mzh  , this was the system first tested , went ok... not fast and not slow when you ran games as quake (GL) ,wipeout2097 etc...

but when it came to games as heretic 2 , shogo and freespace etc , they run like....SLOW! on this card.


so we inserted a 060/66/240 mzh card, also in the same machine,same ram etc.. the os seems much faster (ofcourse its 060 ... , but games like heretic 2,shogo,freespace etc... and wipeout etc...all seems so much faster, and they are much faster.

sadly this is not as good as a 604 with a 060 (on csppc) but its the best thing u can get on a1200 (bppc with 060) , the reason for all this is the amount of context switching needed in one app/gamedemo etc , this is more or less the ppc handing over instructions for the 68k cpu to handle and then the 68k cpu gives it back <-> ,
i could have been more precise when i explained this but my guess u wouldnt read it anyway.

anyway..as a last note... 060 on a blizzppc/csppc works like a dream compared to 040...

cheers

[olegil]

@Karlos:


Why is there an infinite loop in your signature? ;-)

Of course, the new CRAY can run that in less than 4 seconds, but still  :-D

[Framiga]

By bloodine

That's not right... they can't access the RAM at the same time but they can run at the same time, since they both have caches...

i hope so :-)

Imagine the most classic example of an Amiga 68k browser, with PPC datatypes and PPC plugins.

Or an audio NLE app, like ProStationAudio/AudioEvolution4 with theyrs RT DSP runnings under PPC?

Could be perfect! . . .or not?

Ciao

[Karlos]

olegil wrote:
Why is there an infinite loop in your signature? ;-)

Infinite, eh? Take a closer look at the loop condition ;-)

Of course, the new CRAY can run that in less than 4 seconds, but still  :-D

Then it can't be infinite, can it? As for the time, I's say it ought to vary considerably....:-D

[Karlos]

Back on topic, it seems ironic to me that the 060 handles the context swich so much better.

Ok, it has typically twice the clockspeed but also has twice the amount of data to push when it flushes its cache.

In any event, context switching is the biggest hold up on any of the cards. It will be interesting to see how OS4's 68K emulation affects existing WarpOS applications (assuming it is supported) running on these dual processor cards, once the real 68k becomes redundant and context swiching dissapears...and of course the majority of OS (hopefully all) calls will ppc native too :-)

[olegil]

So you have non-crap ideas? Wow, may I worship you? ;-)

[Jose]

@Karlos
 I don't even have time to learn assembler like I wanted  so that stuff will have to wait, but yeah I got the idea. Sounds very cool. Well I could sacrifice some of the "leisure time" but then I woudn't have a life  :-o

[Amiga1200PPC]

Unfortunately AmigaOS4 won't support WarpUP.
But at least the other AmigaOS does.