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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.'"
What's the difference between the Power4 and the PowerPC 970? As a Mac guy, I've been following all of the rumors and announcements with interest but I keep seeing the PPC970 referred to as a scaled-back version of the Power4.
Why wouldn't Apple go with the Power4 over the PPC970? And I already know that nothing official has been announced by Apple and that this is all probably going to be a lot of sturm und drang signifying nothing, but that's what keeps us Mac guys going I guess.
I recall IBM's PPC boards going for over a grand, which is (to me) far too much. Especially when it was a 'G3' chip.
Even if the new chip is faster, will I be able to buy 2 pentium 4's (5?) for the price of it?
I think that since this is a 64 bit chip, why not compare it with other 64 bit consumer desktop chips (ie, AMD Clawhammer)? 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.
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The PowerPC 970 has other potential customers as well, though, not the least of which is IBM itself who, with its large investments in Linux, would love to see a high-performance, 970-based 4-way or 8-way SMP Linux desktop workstation halt the steady flow of former 64-bit *NIX workstation users who began switching to Wintel hardware in the late 90's.
Before all my fellow Mac users start A) thinking about going to Linux B) drooling C) wondering about Darwin or D) some combination of the above, let me remind you that Darwin scales very well. You can now return to your previous state of awe.
PS - How much you want to bet good ol Steve is already having wet dreams about doing the traditional Photoshop test at a Macworld with 4-way SMP?
IT IS ONLY 40 BITS not 64
Your desire to use address pins (or is it max pinned space per process?) to measure size puts you in a distinct minority. That doesn't make you wrong. But neither does it help make you right in this particular jungle.
Systems whose physical addressing match their claimed "bitness" are probably in the minority.
Some systems provide more physical addressing than register width (later PDP-11s, 8086, S/390), some less (68000, classic CDCs, early POWER). The 970 falls into the less category. Nothing unusual there.
Apple, like EVERY OTHER OS KNOWN, will steal a bit or two
Some bits come from physical addresses, some from virtual addresses. These should be addressed [pun slipped in, sorry] separately. AIX, btw, steals less than one bit. Linux can also be configured to steal less than one bit. (Assertions I can get away with no loss of credibility, since AC's have none to start with.) Were you frightened by a VAX in your formative years?
Why do fanboys mod stuff like this down?
Because we can't figure out why someone who needs 512GB, or 1TB, or more (which is it?) cares that a Linux process is limited to 1GB and not 2GB or 4GB.