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Rambus Takes Another Shot At High-End Memory
An anonymous reader writes "Tom's Hardware is running an article about Extreme Data Rate memory (XDR DRAM for short), which was developed by Rambus and now entered mass production in Samsung's fabs. Right now, Rambus says the memory is only for high-bandwidth multimedia applications such as Sony's Cell processor, but the company ultimately hopes to push XDR into PCs and graphics cards by 2006. Time will tell if Rambus has learned from the mistakes it made with RDRAM a few years ago."
before AMD might even thinking about accepting it. Since AMD now puts the memory controller on chip, AMD will have to see proff that it is faster. AMD will not go for DDR until it gets faster. Their reasoning, DDR2 adds cost and decreases performance. Without help from AMD, Rambus might be heading down the same track.
SRAM is much faster, closer to the core of the CPU, and plentiful (if the chip manufacturers wanted it to be).
Who needs a gig of RAM when you can have a gig of cache?
If they need swap space, they can always write back out directly to a disk-based swap file.
if they plan on charging exorbitant prices for their memory again. I inherited a network full of fairly fast (2ghz) Dell boxes using RAMBUS. Sure is fun spending about $300 for a 512 upgrade. Of course you can only install this crap in pairs so there goes your slots.... Junk.. Rather buy a cheap new box than a memory upgrade using this overpriced crap.
This guy is way out there
Smart plan not to try to make it main RAM. By going after multimedia applications like HDTV, video games, etc. they're targeting a market historically willing to pay a premium to get the best performance. I'll be really interested to see the graphic cards based on it and how they compare with the alternatives.
Start a happiness pandemic
I don't visit Tom's as a matter of principle - it's my feeling that Tom's reviews favor his biggest advertisers, not the best technology. ExtremeTech covers the same topic here: http://www.extremetech.com/article2/0,1558,1188770 ,00.asp
Well, looks like they haven't learned much from their old mistakes, but are trying to avoid the consequences... smart move targetting heavy bandwidth apps for now.
In the long run, if they can't significantly drop manufacture prices to (let's say) 150% or even 200% of "regular" (by that date) RAM, the boost in speed a computer with "XDR DRAM" will get compared to (again, let's say) "PC800 RDRAM" will be not significant... and I'll bet (regular) people would rather choose 8 GB of "PC800 RDRAM" over 2 GB of "XDR DRAM" any time of the day.
Bottom line: they're either stuck with "speciality hardware" (like graphic cards or high-end servers) or they have to drop (manufacture) prices rapidly if they want to keep selling.
By reading this signature you agree to not disagree with the post you just read.
Apple to rebrand it as "RAM Extreme"
Take off every sig. For great justice.
8GB/sec is good but not if the latency is higher than DDR.
People seem to forget that the "Random" part of RAM is kinda crucial.
Tom
Someday, I'll have a real sig.
I have adamantly refused to purchase any system that would use their memory for years, and more to the point have made that decision for others that depend on me making that decision. That's a lot of computers over the years were talking about. I am also far from alone.
150million / 6 = 25 million...
25million bits / 8 = about 3MB.
Parent poster is correct.
Time will tell if Rambus has learned from the mistakes it made with RDRAM a few years ago.
Well, Rambus has expanded their latest lawsuit blitz to include DDR2 patent claims, so do you think they've learned?
1. Fast RAM is still expensive.
2. RAN changes to quick. I buy RAM for one computer, it's only for that computer. No portability.
I get a hard drive, I can put that in my new system. I get a new mouse, can use that on my new system. Display? Yep. Graphics card? Most likely.
RAM? Not likely.
IMHO they need to standardize RAM like AGP or PCI-X. That way users feel more comfortable investing in it... you can upgrade and keep your RAM.
That would be an unusual special case. First off, most (non realtime) 3D rendering isn't terribly bandwidth or latency sensitive. Assuming the CPU is fast enough that it isn't the main bottleneck, such apps will tend to be more sensitive to latency than to bandwidth. When tracing a ray, for example, one may need to access data from all over memory to do hit-testing, but not need very much information in total. So, the relatively poor latency characteristics of RDRAM don't really suggest a keen funtansticness for 3D rendering. And, considering that current single channel DDR400 has as much bandwidth as dual channel RDRAM did... Well, I'm just surprised that your app would have such a benefit. I'd suspect that there were other differences that caused such a difference in your benchmarks. Do you have any more specifc information, such as what app you use, what sort of scene it was, and what the test systems were?
If you were dealing with slightly different steppings of the same CPU (I assume a P4?) it would be possible that you had two CPU's of the same clock speed, but the newer stepping was less efficient per clock. The P4's, over time, have been tweaked to be less and less efficient over time, in order to facilitate higher clock speeds. RDRAM was popular with the very first generation of P4's, so it'd be logical that the benchmark you saw may have been a newer core. That shouldn't explain a 20% speed difference, but it's an example of a small thing that may have contributed to making the memory system appear to be the determinant item in performance.
The test case was intensive ray tracing with Pixar's RenderMan on two systems:
3.06 GHz Pentium 4, 512KB cache, 533MHz FSB, RDRAM
3.00 GHz Pentium 4, 1MB cache, 800MHz FSB, DDR400 RAM
The DDR system is only 86% as fast as the RDRAM system (the RDRAM system is 16% faster). This is despite the DDR system having been purchased almost two years later, and having more cache!
The DDR system does pull ahead for compositing tasks (by quite a bit - in some cases it's twice as fast). I assume this is due to the larger cache.
But ray tracing takes about 90% of my total render times, so it's far more important to optimize. I am disappointed that I can't buy hardware today with the same RAM performance as I got two years ago.
Wasn't Rambus run out of PCs due to their crooked practices anyway? What makes them think people won't forget? Didn't think I was going to hear that name again. (shakes head in grief)
"The introduction of XDR however is reminiscent of RDRAM around 2000/2001. The technology provided significantly more speed than DDR and was promoted by industry heavyweights such as Samsung and Intel."
Actually, RDRAM was introduced around 1995, and was used by industry heavyweights such as SGI and Nintendo.
3.06 GHz Pentium 4, 512KB cache, 533MHz FSB, RDRAM
3.00 GHz Pentium 4, 1MB cache, 800MHz FSB, DDR400 RAM
You're probably comparing a Prescott to a Northwood. They're fundamentally different processors -- way more than a remap from 130nm to 90nm, but share enough I guess for Intel to continue branding it Pentium 4. For example, Prescott has longer L1 latency than Northwood, twice as long L2 latency than Northwood, and longer mispredict penalty (11 more stages). All those latencies add up to not-as-good performance at the same frequency.
It's a tough act for Rambus to carry out; on the one hand, they have to deal with a small group of manufacturers who have (reportedly) been trying to defraud them and put them out of business, on the other hand, they have to rely on that same small group of manufacturers for all of their future revenue, so aggravating them too much is probably also a bad idea.
Of course, it's also possible that the judge was Just Plain Wrong, and Rambus was just trying to get submarine patents in place while they were a member of JEDEC. I don't have the expertise to make that judgement.
Whoever corrects a mocker invites insult;
whoever rebukes a wicked man incurs abuse.
--Proverbs 9:7
Alright. Extreme Data Rate? C'mon, this is RAM we're talking about here, not a goddamned razor.
May as well call it Extreme Data Rate 3D Titanium Mach 5 Turbo 2k5 Deluxe Edition, or some such...
Why don't you use equivalent processors when doing this kind of comparison. Even though the second CPU has 1 MB of cache, it's a Prescott core and can often be slower than the older Northwood at same clock speed because of the much deeper pipeline.
As someone else already said, "people seem to forget what the R in RAM stands for".
What kills RAM nowadays in common scenarios is latency. Whenever there's a cache miss, or a mis-prediction makes you flush the CPU's pipeline and start again, what causes the CPU to stall is latency. You get to wait until that request is processed by the RAM controller, is actually delivered by the RAM, makes its way back through the RAM controller, and only then you can finally resume computing. That's latency, in a nutshell.
And it's already _the_ problem, and it's gotten steadily worse. A modern CPU has to wait as many cycles for a word from RAM as an ancient 8086 would have if you ran it with a HDD instead of RAM. It's _that_ bad.
That's why everyone is putting a ton of cache and/or inventing work-arounds like HyperThreading. And even those only work so far.
And again, it's only going worse. DDR did increase bandwidth, but did buggerall for latency. Your average computer may well yet transfer two words per clock cycle with DDR, but still has 3 cycles CAS latency like SDR had. And DDR 2 has made it even worse.
So FBDIMM's great big advantage is that it lets you have _more_ latency? Well, gee. That's as much of a solution as a kick in the head as a cure for headache.
As I've said, "no, thanks." If Intel wants to go into fantasy land and add yet another abstraction layer just for the sake of extra latency, I'm starting to think Intel has plain old lost its marbles.
A polar bear is a cartesian bear after a coordinate transform.
There's another aspect of latency here that's being ignored. Here and elsewhere in this thread tree folks are talking about circuitry issues, like the memory controller, DRAM itself, DDR, etc. Those are all valid, but there's one more that's being neglected - wires, drivers, and receivers. By simply putting the DRAM somewhere away from the CPU/Northbridge, up on a DIMM socket, you take a big hit in latency. Even getting Zero-access DRAM wouldn't speed things up that much, because of the physical-related delays.
Oh, I agree with your abstraction comment.
Putting faster things into an FBDIMM just won't do that much, because the speed is physically in the same spot. I did an extensive study of this back prior to 1990 and found these results, and the consolidation of L2 and even Northbridge onto the CPU shows that it's still valid, today. Main memory is going to be slow. Main memory is always going to be slow, because that's a side effect of being "big". Main memory is always going to be "big" as long as the appetite for bits exceeds what can fit onto one chip. Learn to live with it.
Incidentally DRAM latency grows beyond minimum the moment you multiplex row and column addresses. There is a Trcd(max) spec where access is purely row-limited, but in practice that's just about impossible - access is almost always limited by Column access. Trade speed for pins.
Beyond that, even SDR traded off latench for bandwidth, compared to EDO. (I've designed both.) I don't think DDR is that bad a deal, compared with SDR, though I haven't actually done a DDR design, myself. At the very least, DDR offers the half-cycle latency options, and the DDR designs have been architected to scale far higher in frequency than SDR ever was.
The living have better things to do than to continue hating the dead.
We are a big section of the opinion makers in computer hardware. We have the ability to affect the public opinion on XDR. To a large extent we were the ones most adversely affected by the last round, and we are the ones who can shift public opinion now.
This should be like a usenet death penalty. The free market is there to reward those companies that serve their customers and punish those that do not. It is a good system, but it tends to have a short attention span. Tell your friends. Tell your purchasing deparment. Keep Rambus from coming back from the dead and send a message to other companies who think about abusing submarine patents. It's the same thing as harsh criminal sentencing, except that the free market has a far better track record of responding to example punishment (that is to say; if you support harsh criminal sentincing, you should support this on the same ideological grounds, and if you don't support harsh criminal sentencing because it doesn't work, you should still support this because it does).
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