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AuthorTopic: The AltiVec Difference  (Read 1545 times)

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Offline Argo

The AltiVec Difference
« on: April 10, 2002, 10:11:16 AM »
There's an article over on O'reilly network about the Power PC AltiVec technology.

"Apple first introduced PowerMac G4 computer systems using AltiVec -- a high performance vector processing expansion to the PowerPC architecture -- in the fall of 1999. Architecturally, AltiVec adds 128-bit-wide vector execution units to the PowerPC architecture. Early versions of the G4 processor had a single AltiVec unit, while more recent versions have up to four units (simple, complex, floating, and permute). These vector units operate independently from the traditional integer and floating-point units. "

Click here to read the entire article.


Offline whabang

Re: The AltiVec Difference
« Reply #1 on: April 10, 2002, 12:02:54 PM »
Ok, I'm no mathematician, but I do understand that part with 3x performance increase.
Heck! I even remember enough from college math classes to understand some of it!  :-)
Beating the dead horse since 2002.


  • Guest
Re: The AltiVec Difference
« Reply #2 on: April 10, 2002, 05:46:32 PM »
IBM had promised similar, faster Floating Point Unit with 1 GHz / Faster PowerPC G3 CPU.
Unfortunately the unit is NOT compatible with ALTIVEC, because IBM does not have the license from Motorola. Perhaps AMIGA can use this CPU.

Offline Bobsonsirjonny

Re: The AltiVec Difference
« Reply #3 on: April 10, 2002, 08:32:53 PM »
HAHAHA! The Irony:

IBM written on the inside of an AmigaOne!  :-D
The REAL BOBSON - accept no immitations!

8 Bloody Tickets!


Some of my drawings

Offline blubbe

Re: The AltiVec Difference
« Reply #4 on: April 11, 2002, 02:05:05 AM »
Ive searched the IBM site for this info earlier
but with no luck, do u have an url for this ?
i      i     i    i   i  i iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii i  i   i    i     i     i      i

Offline Ivan

Re: The AltiVec Difference
« Reply #5 on: April 11, 2002, 05:25:50 PM »
link lib:c.o main.o library lib:c.lib lib:amiga.lib lib:alitvec.lib

Gee, i hope all that drool dosn't short out my keyboard. :)


  • Guest
Re: The AltiVec Difference
« Reply #6 on: April 12, 2002, 04:01:24 AM »
Altivec won't save the world ...

I'm a developer with a lot of experince with SSE2/SSE/MMX and recently some altivec.
All of these extensions  are variations of  the same theme wich is to take 2(64 bit float)-16(bytes) numbers at a time then do the same operation on all four at once.
Thats great when a program has say 4 floating point numbers that should be multiplied with 4 other numbers.

The problem is that programs are seldom  that simple so you end up with lots of instructions  to rearrange  those numbers to fit into the altivec unit which means that you will lose some of the gain.

Altivec also has some not so nice restrictions like it has to have aligned data and that it can't read from normal processor registers (having to go through memory - yuk thats slow).

That said some things (i.e. 2d image manipulation, signal filtering) will go 2+x as fast while more complex (i.e. raytracer) stuff can be hard to get to run faster at all.

The biggest problem is that since noone decided that  all amigas will have altivec all programs will have to have two code paths for the computation intense parts. This means fewer will bother to write code for it and those who do wastes some time having to support both code paths.

Altivec or no altivec a new amiga with a PPC (not hogged by a crappy old 68k processor)  would be extremely fast anyway thanks to that mean and lean OS we all love.