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Design Philosophy of the IBM PowerPC 970
D.J. Hodge writes "Ars Technica has a very detailed article on the PowerPC 970 up that places the CPU in relation to other desktop CPU offerings, including the G4 and the P4. I think this gets at what IBM is doing: 'If the P4 takes a narrow and deep approach to performance and the G4e takes a wide and shallow approach, the 970's approach could be characterized as wide and deep. In other words, the 970 wants to have it both ways: an extremely wide execution core and a 16-stage (integer) pipeline that, while not as deep as the P4's, is nonetheless built for speed.'"
Kudos to the Ars team yet again for going deeper into CPU designs than 99% of the populace need to go :)
This chip could be the start of something big in the Linux space as well. Think about it, we are now at a point where a few companies other than Intel are now poised to take the center stage in the next gen workstation, most notably AMD, Apple, and now IBM themselves.
While Linux has run on PPC chips for a long time, it is difficult to come upon a G4 chip without paying the "Apple Tax" for the hardware. If IBM steps up to the plate with this chip, which can then run OS X, Mach, Linux, *BSD, (insert other OS'es here), and can be purchased directly or in a package from IBM, we may see a good set of Windows challengers for the desktop and server room. Obviously OS X will still only run on Apple derivatives.
These chips will be big, I guarantee it, and not just for Apple. It will be interesting to see if Microsoft ports Win XP to these chips.
Why would they want to?
Intel and AMD have the x86 market pretty well locked down.
More importantly, why would ANYBODY want to implement the x86 ISA (Instruction Set Architecture or smtn like that). It's the most horrid instruction set in use today.
Some instruction sets can't really be mapped to others easily, and optimizing for good performance with PPC would probably not have good x86 performance anyways.
In Pentiums and Athlons, the instruction set isn't really emulated. It's translated to a smaller instruction set (uops, iops, pick whatever term you like and run with it). However, these smaller sets are still made pretty much specifically to cover the overlying ISA (x86 in this case).
I think Apple will stick with a company that it knows, IBM, since they have been working together for years. It doesn't seem that Apple will just jump ship to the x86 platform. This would also mean redoing the Mac OS X code and optimization (not like they will have to do some anyway, but they will have to do more). It is highly unlike that Apple will go with a heat producing, energy wasting x86 Intel chip.
Apple will almost certainly go with 970 and not switch to Intel for the following reasons: 1. It is difficult to emulate PowerPC with Intel (although the reverse isn't *that* difficult). Apple would need a PowerPC emulator so that all that software (including OSX software) isn't lost. 2. Apple wants to differentiate itself somewhat from the PC. 3. IBM appears to be moving up after the several years of problems with Motorola. The downside is that by the time a 970 board is out it will definitely be in the middle of the pack relative to the PC world. That means that Apple still will have computers that are more expensive than the PC world and that aren't as fast. Of course I think OSX is sufficiently better than either Linux or WinXP for a workstation that I'll stick with it. But Apple best hope that IBM gets large yields on time and perhaps with better speeds than expected.
As was mentioned in this previous article, Mac has been maintaining a seperate port of MacOS X for x86 in synch with the PPC version... I still remember some promotional material pre-OS X talking about an x86 version of Mac OS X being released that lacked the functionality to run Mac OS Classic apps (I think it was called Blue Box?). ;)
;)
Are they going to jump ship to x86? Not likely if they can help it... but they're keeping the option open. Kind of like how Dr. Evil KNOWS his plans will never fail, but he always has that Big Boy rocket hidden in the back--just in case.
And who ya calling energy wasting? My Palomino keeps my room nice and toasty on those lonely nights and makes great julienne fries!
Maxim: People cannot follow directions.
Increases in truth directly with the length of time spent explaining them
finally they'll see that clock speed does make a difference Clock speed is something Intel uses to bolster their performance claims and give people an excuse to upgrade to the newest model. Clock speed tells very little about the performance of a computer. Look at AMD's athlon. Many reviews like the ones on tom's hardware show that running Windows on a "slower" athlon yeilds better performance than a comparably clocked P4. If you meant that finally, if apple runs on x86, there will be a better benchmark between Windows and MacOS, you would be more accurate. Until that happens you are comparing two different fruits.
0xfeedface
i understand that comparing intel and g4's is apples and oranges and that intel uses clock speeds for marketing as well. however, why do you think there is such a huge overclocking market? it's simple: clock speed does make a difference.
Were you by chance looking at PowerPC evaluation boards? Those are low-volume boards intended for prototype developers only and thus, somewhat more expensive than high volume boards.
Tom
Sure, clock speed makes a difference, but only on the same chip. The post I was commenting on implied that you could compare the clock speed of an Intel machine to the clock speed of an Apple machine. For such a comparison clock speed is wholly irrelevant.
P.S. My 333Mhz P2 runs great at 400Mhz, but largely because Intel underclocked the identical core to run at 333Mhz. Intel plays up the importance of clock speed, so they do dumb things like underclocking, and multiplyer locking.
0xfeedface
...an extremely wide execution core and a 16-stage (integer) pipeline that, while not as deep as the P4's, is nonetheless built for speed.
:-)
For those not planning to read the article, I wanted to mention the following so you do not get the wrong impression. The speed that the article refers to (of a long integer pipeline, like a 16-stage or like the Pentium IV's 20-stage) is clockspeed, not necessarily actual performance. The P4's super long pipeline, for example, allows it to run at higher clock speeds, but less work gets done in the same number of clock cycles. This is the "braniac" vs "speed demon" philosophy (with a high clock speed but low instructions-per-clock representing "speed demon") and neither is necessarily better than the other (though one is obviously better for the marketing dept.)
Just don't assume that "built for speed" always means "built to be fast" -- a confusing but important distinction.
Computer Science is no more about computers than astronomy is about telescopes. --E. W. Dijkstra
A lot of Intel's questionable moves (12K micro-ops instruction cache?) for the P4 were obviously not copied by AMD, and x86-64 seems to be the 64 bit desktop chip of the future.
The P4 has its flaws, but IMO cacheing decoded instructions isn't one of them. It shortens the pipeline, and paves the way for a true trace cache (cache of decoded basic blocks indexed by entry point; very handy for renaming and scheduling).
I specifically said, "I dunno 'bout Macs..." because I wasn't trying to make a "See? Intel is better than Mac" post. I was just giving the date at which Intel introduced their first 32-bit processor.
And now that you mention it, I do remember reading that the M68k was 32-bit, but it only had a 24-bit address bus, which meant the max. amount of RAM it could physically have was 16 megabytes. Again, I'm not trying to bash anybody, I'm trying to point out that your "64-bit CPUs aren't really 64-bit because they only have a 48-bit address bus" argument is flawed.
Why you went off on the whole Apple vs. Wintel thing is beyond me, but if you want to play ball, OK. For the record, the PC wasn't meant to compete with the Lisa or the Mac, and both of those computers were introduced after the PC. The original IBM PC was a competitor to the Apple II, but more oriented towards business use rather than home use. If you remember, the Apple II also used a cassette tape drive (just like the original PC), but, like the PC's successors, the PC-XT and the PC-AT (all modern PCs are descended from the PC-AT), later had the ability to use floppy drives and hard drives.
The 1982 lisa had windows, scolling, dialogs, fonts, buttons, WYSIWYG text editing with graphics, etc.
Which were all "borrowed" from Xerox PARC. The fact that Apple later whined and bitched about Microsoft "borrowing" those ideas from the Lisa and/or Mac (when Apple themselves had stolen those concepts from somebody else in the first place) is too amusing for words. I can't stomach Bill Gates, but I have just as hard of a time putting up with Steve Jobs ("You stole Windows! It's not fair! We stole it first!").
And as for Mac OS always being 8 years ahead of Windows, well, I'm no lover of Windows, but Windows had preemptive multitasking years before Mac OS (Windows got it in Win95, Mac OS didn't have it until OS X).
the Apple II had 75% of us market
Although I don't have any hard facts, I have a hard time with this. It wasn't like IBM and Apple were the only players in the personal computer market. There was Commodore with their highly successful Commodore 64 computer (not to mention the Commodore PET, VIC-20, and Commodore 128), Sinclair, the TRS-80 (from Tandy and RadioShack IIRC), and a whole host of others.