How much would DDR help the Power Macs?
From everything I'd heard until recently, the current Power Mac is suffering terribly from a lack of internal bandwidth. In the dual gig models, it has been said that the two CPUs are starving for data to process, because the slow system bus can't keep them fed.
But lately, I've heard a couple of people say that if the Power Macs didn't get DDR and a fast FSB right away, it would be no biggie. That good-sized L2 and L3 caches solve most of the problem, and that DDR would only help squeeze out a few percentage points of increased performance.
I realize that different benchmarks and different tasks could yield very different results. But for overall, general use, and assuming we're talking about processor-intensive rather that I/O intensive tasks... what's the story?
But lately, I've heard a couple of people say that if the Power Macs didn't get DDR and a fast FSB right away, it would be no biggie. That good-sized L2 and L3 caches solve most of the problem, and that DDR would only help squeeze out a few percentage points of increased performance.
I realize that different benchmarks and different tasks could yield very different results. But for overall, general use, and assuming we're talking about processor-intensive rather that I/O intensive tasks... what's the story?
Comments
No doubt about it, the Powermacs could use the fastest memory controller Apple can ante up. And no doubt about it, Apple is going to go cheap like they always do.
<strong>From everything I'd heard until recently, the current Power Mac is suffering terribly from a lack of internal bandwidth. In the dual gig models, it has been said that the two CPUs are starving for data to process, because the slow system bus can't keep them fed.</strong><hr></blockquote>
Well, that's true. And it's also true that a good L2 or L3 cache can fix the issue.
Problem is that it entirely depends on what you are using the machine for. General purpose usage, fast caches will help a lot, but toss a 80MB TIFF into Photoshop and those caches won't count for much.
The Altivec units in the dual gig can theoretically eat up somewhere near 20GB/sec. and there's not a damn thing in any of our price ranges that can feed those buggers. Of course, we're talking pretty specialized (and uninteresting) tasks. Still, for digital video, audio, photo work, publishing, and computation, memory bandwidth is usually pretty important.
Thank god Apple isn't targeting any of those markets. <img src="graemlins/hmmm.gif" border="0" alt="[Hmmm]" />
<strong>How long has DDR been out on the Dark Side?
About 18 months.
Because now it's a joke...seriously, compare the current Powermacs to even year-old midrange Wintels, and they are antiquated. But they cost a fortune.
It doesn't surprise me one fu[king bit that Apple can't move their Powermac inventory, who the hell wants to buy when it's so obvious that Apple will update? At least after an update Apple will only be one generation of technology behind Wintel, now they are 2 generations behind, moving on to 3 generations behind. It's like a Mac Plus selling against a Pentium Pro....a total joke!
That's what I say, Apple just cans the Powermacs for a year or two until the G5 is ready, tells their professional customers, "we have nothing to offer you for now, so in all honesty, we would rather not rip you off with any "two brains are better than one" idiocy."
<strong>right after mwny, dual-channel ddr is going to be released for intel/amd chips. apple is so far behind its not even funny.</strong><hr></blockquote>
I'm pretty sure there's no rule that says that Apple can't just skip right to dual-channel DDR. Someone even suggested (maybe Dorsal) that dual-channel DDR might show in the next 12 months.
<strong>
Well, that's true. And it's also true that a good L2 or L3 cache can fix the issue.
Problem is that it entirely depends on what you are using the machine for. General purpose usage, fast caches will help a lot, but toss a 80MB TIFF into Photoshop and those caches won't count for much.
The Altivec units in the dual gig can theoretically eat up somewhere near 20GB/sec. and there's not a damn thing in any of our price ranges that can feed those buggers. Of course, we're talking pretty specialized (and uninteresting) tasks. Still, for digital video, audio, photo work, publishing, and computation, memory bandwidth is usually pretty important.
Thank god Apple isn't targeting any of those markets. <img src="graemlins/hmmm.gif" border="0" alt="[Hmmm]" /> </strong><hr></blockquote>
A L2 or L3 cache cannot make up for a slow bus except under specific circumstances, and as you point out yourself, whenever new data is called for the caches are useless. It's preposterous to say that a L3 cache will fully compensate for a slow bus.
And just because Apple cannot offer something that will totally feed the altivec units, that doesn't mean they shouldn't offer the best that they can. The fact remains that in many instances for the G4, the bus is the rate limited step for processing data. Any improvements in bus thouroughput will show benefits, it doesn't have to be a $20000 solution to see benefits.
And you contradict yourself again, when you say that altivec isn't used except for specialized, uninteresting tasks. On the contrary, most multimedia processing can be optimized for altivec.
I guess you just had to get a word in, eh?
The key is, since the bus is the bottleneck on the current G4 systems, ANY improvements in bus bandwidth will translate into immediate and recognizable improvements in system performance. Whether it be DDR, or even PC166, or even PC150 (does it exist?), the improvements will be tangible.
Now that DDR is essentially the standard memory architecture for PCs, it would NOT be expensive at all for Apple to implement such a memory system in their Powermacs. The problem once again is in Motorola's hands, and until they supply Apple with a G4 that can support anything better than PC133 RAM, they essentially have Apple's nads in a vice. The only question is how quick they tighten it.
Rumors of an IBM-produced G5 appearing in late 2003 are downright scary....it's too little, too late. By late 2003, the G4 will be several generations behind whatever Intel is supplying for PC boxes. The performance delta between Macs and Wintel will be so staggering that only fanatics and "consumers", ie, home users, will still be using Macs. Professionals will abandon the Mac platform when the performance differential is so vast that Wintels can run apps like Photoshop at 4-6 times the speed of a Mac....don't laugh, that day is soon coming...unless Apple has an ace up their sleeve.
<strong>...unless Apple has an ace up their sleeve.</strong><hr></blockquote>
<strong>The performance delta between Macs and Wintel will be so staggering that only fanatics and "consumers", ie, home users, will still be using Macs. Professionals will abandon the Mac platform when the performance differential is so vast that Wintels can run apps like Photoshop at 4-6 times the speed of a Mac....don't laugh, that day is soon coming...unless Apple has an ace up their sleeve.</strong><hr></blockquote>
So put your money where your mouth is.
So sure of this are you? So go buy a new PC and start converting data while privately laughing at us, so that when the day comes you'll be ready to lay back and laugh at everyone. That certainly would make you happy wouldn't it JYD?
Don't give me the "I love my Mac 400, etc etc etc" garbage. We've heard it. You look for any opportunity to rub in anyone's face that Apple's a) made a mistake b) making a mistake or c) will make a mistake. Exactly how many times have you typed "Apple is DOOMED!" because I know that everytime I have in recent months its been just referencing you. And yet you stick around here. I still think you're bipolar--you should have that checked.
This isn't a forum for insults, which is why I'm not being childish. I just think you need to relax and make up your mind about which camp you are in, as opposed to sitting on the fence making fun of both sides. What kind of army do you think would win a war if their soldiers sat in the battlefield and cried about how doomed they were because the other side had bigger tanks? Round here in the States we won a couple wars against the British, when they had the superior hardware...now we're saving THEIR asses in wars
Just please please please stop depressing people. Keep it to yourself every once in a while. We all know how hopelessly misguided you are to think that a P4 is a good chip
As far as DDR goes, it would help a significant-enough amount that you'd notice. I can't give a % amount but load times (apps, games, etc) would be a lot shorter, thats for sure.
We're tired of you JYD.
ting5
--
Ed M.
If we got a true DDR, even without any improvements to the G4's clock speed, we'd be in very good shape.
Also I don't think Motorolla is ready w/ DDR--I think Apple's gonna get another creative solution between the Xserve's solution and true DDR speedwise, but even so this would bring Powermac's and PC's onto a level playing field.
Just to add this to the "PC's are better and cheaper" ordeal, none of you seem to remember that Dell and such companies don't make money off of their consumer and prosumer markets, that's why Gateway's going out of business. Apple has healthy business practices and can continue to keep it's prices steady for a while, PC prices have to go up eventually or they're all going to be doomed.
(edit, some UBB code in the wrong place)
[ 07-10-2002: Message edited by: rightnow 92 ]</p>
<strong>
So put your money where your mouth is.
So sure of this are you? So go buy a new PC and start converting data while privately laughing at us, so that when the day comes you'll be ready to lay back and laugh at everyone. That certainly would make you happy wouldn't it JYD?
Don't give me the "I love my Mac 400, etc etc etc" garbage. We've heard it. You look for any opportunity to rub in anyone's face that Apple's a) made a mistake b) making a mistake or c) will make a mistake. Exactly how many times have you typed "Apple is DOOMED!" because I know that everytime I have in recent months its been just referencing you. And yet you stick around here. I still think you're bipolar--you should have that checked.
This isn't a forum for insults, which is why I'm not being childish. I just think you need to relax and make up your mind about which camp you are in, as opposed to sitting on the fence making fun of both sides. What kind of army do you think would win a war if their soldiers sat in the battlefield and cried about how doomed they were because the other side had bigger tanks? Round here in the States we won a couple wars against the British, when they had the superior hardware...now we're saving THEIR asses in wars
Just please please please stop depressing people. Keep it to yourself every once in a while. We all know how hopelessly misguided you are to think that a P4 is a good chip
As far as DDR goes, it would help a significant-enough amount that you'd notice. I can't give a % amount but load times (apps, games, etc) would be a lot shorter, thats for sure.</strong><hr></blockquote>
Jesus, taking things a bit too seriously are we? He can sit on the damn fence if he wants too. And we aren't in some huge computer war so just cool down there dude. And I think you were being quite childish but whatever. JYD can defend himself if he wants to.
I think true DDR implementation and at least 1.2Ghz on the low end PowerMac and Apple MIGHT then have something going and be able to convince former PowerMac customers to come back. I hate it when people go "oh well Pentium 4's suck, do you really want one of those?" Well sorry to break it to ya people but that "sucky" chip powers computers that can kick our Macs' asses.
The only real leap forward has been RDRAM, and that's only in the case where it's streaming a big chunk of contiguous memory.
Apple could in fact have an ace up their sleeve if they do something radical like NUMA and/or an on-chip memory controller and HyperTransport (or RapidIO) combination. That would give them the potential to leapfrog most other offerings in terms of bandwidth to the CPU, and it would give them an architecture with a lot of room to grow. I think HT can manage up to 16GB/sec down the road.
Oh, and a note for JYD: Due to a phenomenon called "locality of reference," caches (and large register sets) are useful almost all of the time. The only real exceptions are big streams of memory, and MaxBus has streaming instructions efficient enough to just about reach its theoretical bandwidth reading and writing those streams. It's as fast or faster than PC DDR SDRAM implementations, although it can't keep up with RDRAM. Nevertheless, the voracious 7455 - and in particular its AltiVec unit - want more.
[ 07-10-2002: Message edited by: Amorph ]</p>
That's not to say the latest x86 machine isn't faster than the latest Powermac in many respects, but I think the majority of what people are talking about is pure Mhz envy.
If you (not speaking directly to G4dude who posted before me, but anybody out there) can say you've used both, you've compared them, and the P4 2.4ghz runs apps twice as fast as your dual G4 1ghz, then fine. If you're still running a G3 400 at home and using a Celeron 400 at work and you're just speculating that these machines you've never used MUST be X amount faster in practical use, then your opinion is based on nothing.
The only people who convince me with their opinions are those who have tried the fastest Powermac and the fastest x86 machines, and found the difference for themselves.
If RDRAM is the only real memory bandwidth leap (for large streaming sets) what exactly is holding DDR back? Is it the efficiency of the implementation? ie. the sustained throughput never really approached the theoretical peak? And whose fault is that? Is it a flaw in DDR or is it a problem with CPU/MoBo/chipset makers?
If Moto's and Apple's MPX implementation is so efficient (and manages to come close to the theoretical peak) then how fast relatively speaking would an MPX166 or perhaps a 200Mhz FSB (like the Sahara's) improve matters?
Also, with Video cards set to have a much bigger role in serious computational work and a fatter pipe (8X AGP) wouldn't a competent/highly efficient DDR266-333 implementation be a good thing even if the CPU couldn't talk to memory at that speed? In my naively simple estimation, could this not provide ample bandwidth to both the GPU and CPU without access from one choking of access from the other? Not to mention disk/PCI activity? Certainly for a server DDR looks like a good thing regardless of your PPC FSB constraints, but in light of QE, it could likewise be a very good thing for a desktop graphics machine, or am I missing something?
While I like to rag wouldn't a dual CPU, 166/200Mhz FSB, tied to a 266/333DDR memory controller, and an 8X AGP card make a pretty good QE system?
<strong>
It's preposterous to say that a L3 cache will fully compensate for a slow bus.</strong><hr></blockquote>
True. But there are a lot of consumer users out there that are taking only a negligible performance hit from that bus. To them, that L3 would probably do just about as much. So would a faster HD for that matter, or a bunch more RAM. But if you are a memory-bound type of person, then no, you need the bus fixed.
[quote]<strong>Any improvements in bus thouroughput will show benefits, it doesn't have to be a $20000 solution to see benefits.</strong><hr></blockquote>
Absolutely. But with Altivec we're always going to be memory bound in some cases, so we should recognize the benefits that L3 bring and not spin off onto one of these "f*ck the L3, I want dual DDR or else!" tirades.
[quote]<strong>And you contradict yourself again, when you say that altivec isn't used except for specialized, uninteresting tasks.</strong><hr></blockquote>
No I didn't. I said that Altivec can eat that kind of data only on the most specialized uninteresting tasks. And that's generally true. Some simple Photoshop filters can eat that up, but once you get into any interesting mathematics or image manipulation, then you're going to make multiple passes over the data or bottleneck on the scalar integer unit or something else - the RAM bottleneck may well go away, and suddenly that L3 cache is looking a lot more important. RC5 benchmarks prove that Altivec in that case isn't too horribly bus-bound and might well benefit as much from L3 as from DDR. I've never suggested that Altivec can't do useful, interesting things. Far from it. I'm suggesting that there's no silver bullet, though IMO DDR is needed due to the audience that Apple is targeting with the Pro boxes. It is NOT so much needed for the audience that Apple is targeting with the iMac and iBook.
[quote]<strong>I guess you just had to get a word in, eh?</strong><hr></blockquote>
You sure did. You were the one that called me out...
[quote]<strong>The key is, since the bus is the bottleneck on the current G4 systems, ANY improvements in bus bandwidth will translate into immediate and recognizable improvements in system performance.</strong><hr></blockquote>
No, the key is that Apple has a fairly broad market, many of whom run into the memory bottleneck and many of whom don't. Looking at the Xserve, I see a LOT of buyers of that product that won't run in to the bottleneck (since it's DDR bandwidth doesn't extend to CPU, it's G4s are as memory bound as any) but will benefit considerably because they are serving files, streaming video, etc. For most of the target market, those G4s are NOT really harmed by lack of DDR. Would it hurt to be in there? Not at all, since I imagine the BLAST users are running into that problem, and clearly they are a target for this product.
[quote]<strong>The problem once again is in Motorola's hands</strong><hr></blockquote>
It's always in either IBMs or Mots hands. On the PC side, it's always in either AMDs or Intels hands.
[quote]<strong>Rumors of an IBM-produced G5 appearing in late 2003 are downright scary....it's too little, too late.</strong><hr></blockquote>
I'm not sure where your mindset of G4 != DDR comes from. Certainly that's been true thus far, buy why can't Mot turn out a DDR enabled G4 right now? Do you really think that Apple will jump right to G5 with no improvements to G4? Clearly the G4 will be around in the iMac and iBook for some time to come, and DDR will likely come along for the ride at some point.
<a href="http://arstechnica.com/paedia/r/ram_guide/ram_guide.part3-1.html"; target="_blank">RAM Guide: Part II: DDR DRAM and RAMBUS</a>
<a href="http://arstechnica.com/paedia/c/caching/caching-1.html"; target="_blank">Understanding CPU Caching and Performance</a>
[ 07-10-2002: Message edited by: Analogue bubblebath ]</p>