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New Power Macs Have Crippled DDR Memory?
eggboard writes "According to Rob Art Morgan, who has tested this, the new Power Macs from Apple that use DDR (double data rate) memory -- like the Xserve rank-mount unit -- cannot access the memory any faster than the cheaper and slower SDRAM found in the previous system arch. A controller limits the data rate to 1 GB/s, while DDR could work more than twice as fast. Unfortunately, this makes mincemeat of the architecture, as it bus-/memory-bounds 2D and 3D graphics and rendering."
http://www.macosrumors.com/ has a similarly unfavourable article
I've already discussed this on MacSlash, but the problem is that the G4 processors currently shipped with Macs don't support DDR memory via a direct connection.
The closest Moto has gotten is a 8xxx series "G5" processor that supports a RapidIO interconnect. However, this new processor, despite the existence of demo units dating back years, is still effectively vaporware. My understanding is that Apple is backing an interconnect technology called HyperTransport instead.
Any insiders willing to clarify or correct this? Motorola's current financial state is distressing, especially since I live near where they are based. All those layoffs...
Those who complain about affect & effect on
before drawing any conclusions from this article.
You haven't the slightest idea what you're talking about, do you?
Motorola makes the CPU. Motorola makes CPUs that don't support DDR access to memory.
Apple makes the motherboards. Apple implements DDR memory everywhere except in the CPU.
IBM just announced vector computing support in the Power4. Vector computing is a big part of Apple's strategy, and until recently it was only available from Motorola.
The new Power Macs have a heat dissipation mechanism that's capable of dealing with many times the heat load of the currently shipping systems. They added this feature despite the fact that the previous generation of Power Macs had no particular heat problems.
Can't you read the writing on the wall? Apple has designed this new Power Mac to accept new, faster processors, and lots of 'em. A four-processor system is not unreasonable given the amount of space and heat dissipation inside this new chassis. Six or eight processors might even be possible, if everything comes together just right.
Don't assume you have the first idea what Apple has planned until you get all the facts.
Why does this strike me as so typically 'blame Apple for everything'?
The real story as I understand it is quite an old one - Apple is screwed because of the continued dependence on Motorola. You see, the G4 processors made by Motorola can't connect directly to DDR memory, requiring this type of kludgy go-between.
I for one am all for seeing Apple abandon Motorola within the next couple of years...and PPC in general if need be...and move to cheaper comodity CPU parts by Intel or AMD. I suspect we could kiss goodbye the tiny, quiet, cool (temperature) designs...but it probably will be worth it.
You like your Macintosh better than me, don't you Dave? Dave? Can you hear me Dave?
My rackmount server is going to suck at 3D games. Crap.
The base configs of each machine are NOT listed.
The base OS configs of each machine are NOT listed.
The combined running configs, ie, size of objects, optional software (especially 3rd party apps and gui-players), etc, etc.
Guess what - each of the above - without running a single line or click of a benchmark can help in determining the outcome.
I'll wait to see how bad or good the new machines are - but I can tell you in advance, the old dual 1Ghz machines and the new ones are not identical at all in the CPU area.
Some folks have to learn to read and understand specs before jumping up and down and screamming.
Just my 2 cents, from the peanut gallery here in NY
Gil
-- Where ever you go, don't complain, you went there!
I think Apple is definitely positioning themselves to be capable of moving to Intel quickly if needed. But I have a feeling they will go IBM if at all possible. The PPC hardware is superior to Intel's hardware, and I think Apple wants to stick with this sign of quality.
Then if that falls through somehow, they'll be ready to move to Intel.
Just my feeling on it.
If you want to make an apple pie from scratch, you must first create the universe. -- Carl Sagan
The DDR is underutilized only for CPU based operations. DMA and AGP based operation will get a boost from DDR.
The data rate between CPU and RAM is limited to 1.3 GB/s. However there is still more than 1.3 GB/s of bandwidth for the GPU (AGP 4x which goes at about 0.5 GB/s), DMA calls from hard disks, etc. So graphics and rendering are not strictly bus-limited, as the GPU can never fully stress the bus. Furthermore, the GPU wasn't tested in the BareFeats benchmarks!
Furthermore, don't forget that the L3 cache on the new 1GHz Macs is only 1 MB, not 2 MB as it was in the previous 1GHz Macs (and as it remains in the 1.25 GHz Macs).
All these benchmarks teach us is that CPU-limited tasks like those posted at BareFeats are not a good test of the added throughput between the system controller and RAM. We need to see benchmarks that stress all of the throughput, not just the portion between CPU, controller, and RAM.
Can't you see that everyone is buying station wagons?
So we have an article which misses a few important points at the generally iffy barefeats, this is then compounded by the comment "cannot access the memory any faster than the cheaper and slower SDRAM" which misses the mark even further. It's a real shame when these things spread around as "the truth" especially on somewhere like slashdot.
Yes the new motherboards are not full DDR, this is mainly because the processors available from Motorola cannot handle DDR FSB's and therefore a full DDR motherboard. This is a shame, but it is far from crippled DDR RAM. Many early DDR RAM x86 motherboards were the same, only the RAM was DDR, not the full motherboard and processor FSB. While this does mean there is still a bottleneck (in certain tasks) between the processor and other components there are advantages to having DDR RAM. The tests at barefeats are using purely CPU limited operations, which will obviously show no real improvement as there has been no CPU or bus change (although the new 1Ghz procs have only 1Mb of DDR L3 cache versus the old 2Mb DDR and a 167Mhz bus version is available). What DDR RAM will help with is when there are a variety of components (CPU, HD, network, AGP, PCI, Firewire, etc) all vying for valuable memory bandwidth. It's these 'real-world' situations when we will see a performance increase. If you just run single process, purely CPU intensive tasks then maybe these machines aren't for you, but if you run a lot of stuff at the same time, or anything that uses CPU, HD, AGP etc intensively and concurrently then you should see an improvement. Things like Quartz Extreme will be throwing a LOT of data at the AGP bus, with DDR RAM this won't have to wait it's turn while say your CPU is busy grabbing all the bandwidth. I'd say many users have a lot of HD, CPU, GPU and network activity going on simultaneously, especially 'power' users. Hopefully we'll see some more benchmarks that show a variety of tasks being performed on these new machines once more people (and more reputable sites) get hold of the machines. While not fulfilling everyones dreams, I'm sure that the statements about the DDR RAM additions being a "waste" or "crippled" will be shown to be entirely false.
Apple's pro iron today is quite expandable. If a new IBM chip arrives that can handle DDR memory as it should, your investment in a new Power Mac will pay off in spades with an upgrade from places like PowerLogix and Sonnet. I just upgraded a now-3-year old Power Mac G3 Blue and White (the first Macs with the current pro chassis) from a 350MHz G3 to a 550MHz G4. With OS X on it, this system rocks...and now I'm reticent to sell it as planned.
In any case, the new systems are still a great buy. It's a UNIX box, folks. More processors mean more processes. At least the systems aren't SLOWER. I take the benchmarks from Bare Feats with a grain of salts. As the saying goes, your mileage may vary. I'm betting these systems will rock when the Mac version of Jedi Knight II shows up.
Vos teneo officium eram periculosus ut vos recipero is.
Why would Apple roll out a new chassis design without the chip that would need it?
Two apparent reasons:
(1) Apple wasn't selling near the PowerMacs that they were a year ago. The line needed something shiny and new.
(2) Apple was probably designing this new motherboard for a CPU that can handle HyperTransport (hopefully the next PowerMac) and decided to release it now for reason (1).
That's the way I see it, anyway.
-- My hovercraft is full of eels.
IBM won't license Altivec from Motorola, so they can't make the "G4" Chips that Apple wants and needs. Actually, if I remember right, it was an Apple Engineer who came up with Altivec, and Motorola implemented it because they could also benefit from it.
Unfortunately the AIM alliance partners seem to have increasingly divergent needs from the partnership. IBM wanted PowerPC for servers, and sees Altivec as a gaudy tack-on to their architecture. They still produce the "G3" chips, at ever higher and higher clock speeds. Apple can't use them though because of the MHz. myth. IBM's stance towards Altivec appears to be weakening though with their upcoming chip.
Motorola wants PowerPC for embedded stuff, and Altivec makes it easy to do DSP like functions in a general purpose processor.
Apple needs the PowerPC for everything but the iPod. They need Altivec to make MacOS X so cool for consumers and scientists. Since IBM won't license it, they are stuck with the only producer, Motorola.
It's times like these that I wish there were some truth to the old rumors about Apple buying Motorola's PowerPC fabs. If that were the case, Apple could produce the exact chips that Apple needs, not what IBM or Moto wants. Unfortunately, there isn't any indication that this would be profitable or feasible for them.
-- Len
Fo the record: Apple does use IBM chips. Every G3 the ship is an IBM G3, including 700 MHz models, which is, I think, the top of IBMs line right now. My money's on the "G5" being a version of the Power4 chip, and Apple and Moto will go their separate ways.
I am a believer of momentum and curves.
Personaly, if they go with any PC chip company other than IBM, I have a feeling that Apple would choose AMD. Not because of any technical minded reasons, but simply because of image. For a long time (and still today) Intel is associated with Windows. And to have the logo that says Intel inside, implies that it is PC compatible.
If apple went with intel, they would piss off the rabid fans, they would piss off the PC comunity, they would piss off the anti intel people and they would cause sever issues for new users.
But that' just me talking
T Money
World Domination with a plastic spoon since 1984
What I haven't heard anyone talking about is some of the groundwork laid out for later, when they can remove the CPU bottleneck. Some of the more interesting features of the Xserve architechture are: Intervention and Write Combining. Funny, the things revealed by a little research...
I'll keep my QuickSilver 933 for now. Jaguar promises good performance gains, and that's worth the $129 if I save about one hour for one client. (or worth about $500 if Jag gives me an extra hour of quoteunquote free time)
cat
Since when was showing off your best face and not wanting to play on the opsitions home turf considered bad? Seriously, I never trust any benchmarks put out by anyone. I like real world user experience. When I sit infront og the machine and use it, that's what counts in my book, not some spec number that says that my Athlon can overclock nearly 80% and that it can do my laundry too. Nor do I trust apple's demos. It's all a mater of user experience. How else do you explain all those people using old computers and linux?
T Money
World Domination with a plastic spoon since 1984
And of course, name calling while hiding behind a viel of Anonymity isn't reactionary at all? Or freak ish? Seriously, the people that do come here for serious discussion do get fed up and leave because of people like you and the fact that slashdot seems to have more baka than geeks these days.
T Money
World Domination with a plastic spoon since 1984
Even IF (big IF) they are the same, notice the giant price drop you just got. So stop whining and start buying. If they have more money to develop with, you'll get a better machine. Doesn't anyone understand long term investing anymore?
T Money
World Domination with a plastic spoon since 1984
Because by having a future compatible chassis now, they can spend more money on developing chips and getting Moto to shape up. They had the money to go forward, they went forward. Now they just need to develop the finishing touch, and they get a surge of new money from the new tech, all to dump into the finishing touch.
T Money
World Domination with a plastic spoon since 1984
Altivec was created in a joint effort between Apple, IBM and Motorola. They all have patents on the thing, but use different names for it. Motorola owns the name Altivec, Apple the name Velocity Engine and IBM used to call it VMX. AFAIK they all have the right to use the instruction set (but not a name or specific implementation they don't own). The reason why IBM didn't use it was because they didn't see the use of a vector processing unit (in the past). Of course, the G4, Pentium III & IV and the Athlon have shown the usefulness of a vector unit and IBM has changed their stance. The best proof is of course the new 64 bit PowerPC. It has a vector processing unit which almost certainly is Altivec (although they won't use that name). The Power5 will probably contain a vector processing unit as well.
It is clear that Motorola and Apple have grown apart. Apple has had big problems with them for a long time and has looked at other options. They didn't choose to buy Motorola's awful fabs, it's too late to do that know (nor is it smart). No, credible rumors point to IBM. It makes a lot of sense:
- IBM wants to sell more low-range (Linux) servers, so they already need a fast desktop CPU. Why not sell it to someone else as well?
- Apple has a lot of experience with Altivec, it makes sense to work with them to produce this chip (Apple employs some very smart chip-designers).
- Altivec is a respected instruction set. It's proven to work (no need to reinvent the wheel on a risky venture). Tools are available. GCC supports it (and since their servers will run Linux...).
In 6-9 months we'll probably have a 64 bit PowerMac that is very competitive. I can't wait.
The Drowned and the Saved - Primo Levi
And for what it's worth, Slashdot's article selection has been nothing, if not pro-Apple.
Says the RIAA: When you EQ, you're stealing bass!
I think the "1 GB/s" was taken from a comment in the original review on Bare Feats. There was an "explanation" posted from a reader that made the bogus claim that the memory bandwidth was limited to 1 GB/s even in the models with a 166MHz system bus. I notice that the revised Bare Feats report has removed that whole section.
Anyway, the thing that stands out about these benchmarks is that the new dual 1GHz has a system bus (and memory bandwidth) that is 25% faster than the old one, yet this made no discernable difference in these particular benchmarks. This isn't surprising considering that these are CPU-intensive tests, but the bizarre thing is the number of people who are claiming that this somehow proves that the DDR implementation is useless, a fraud, etc. etc. They seem to think these benchmarks would improve dramatically if the DDR bandwidth was passed on to the CPUs.
This isn't logical. Why would a real 25% improvement in memory bandwidth have no influence at all on the benchmarks, yet a 100% improvement which would come from a "real DDR" implementation suddenly make a big difference.
The results of these particular benchmarks would be the same because they are CPU intensive tasks and therfore are bound by CPU speed. (That is, for these tasks much more time is spent in CPU processing that in reading or writing memory). There's no magic change Apple could make in other parts of the system that will make 1GHz CPUs process faster than 1GHz.
That isn't to say that the 166MHz system bus and the DDR implementation Apple is using isn't advantageous in generaly system usage, it is just to say that these benchmarks will not reveal those advantages.
- Dennis D.
Oh, please! Be fair, the machines didn't just "not go up in price." They went down in price! The new dual 1GHz machines now sell at the mid-level price, several hundred dollars less than the old 1GHz. Even if the performance was basically unchanged across the board (which I don't beleive the Bare Feats benchmark proves anyway) the price/performance ratio has definitely improved.
- Dennis D.
The only major manufacturer that seems to be missing official SPEC results is Apple. Instead, we get bogus and irreproducible benchmarks like Photoshop and Bryce, both from Apple and from benchmark sites like these.
Why? Is Apple afraid of backing up their claims of "supercomputer performance" with actual facts? Inofficial SPEC benchmarks have shown the G4 not to be all that much faster than a Pentium with similar clock speed.
You make a good point, and I must say, if I imagined Apple switching to a PC chip company, the thought of AMD sits much better with me. Also, I get the feeling that AMD is overall better quality than what Intel puts out.
Haven't heard any rumors about that though, surprisingly.
If you want to make an apple pie from scratch, you must first create the universe. -- Carl Sagan
Does anyone know if these benchmarks test memory throughput at all? I have no idea what the Photoshop "MP" action file test is, or why it's there twice, so I'm mainly curious about that. I can't imagine that MP3 encoding or rendering in Bryce aren't completely CPU-bound.
I'm not a smorgasbord.
"Flamebait"? Come on, contribute something constructive. Heise's applications of the SPEC benchmarks show that G4's are not performing much faster than a Pentium at similar clock speed. If you believe that those benchmarks are wrong, describe your reasoning. So far, I have not seen a single criticism of Heise's benchmarks that would alter those conclusions.
So, of course, pointing out that the article is a troll and flamebait is the equivilent of trolling and flame baiting and my post has been moderated as such.
Yeah, Slashdot is really pro-apple.
Sheesh.
There is no science here, no rationality, no technology. And its sad. There should be a place for geeks to congregate online.
Yeah, and you guys panned the ipod too: http://apple.slashdot.org/article.pl?sid=01/10/23