SDRAM vs. RDRAM, Facts and Fantasy

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ArticleRobot

New Member
#1
In this article you’ll find an in-depth analysis of Rambus’ RDRAM, what makes it tick, what the benefits are and above all we’ll look into its technological advantages and widespread misconceptions. We’ll round up this article with a broad range of real world benchmarks, which are aimed at finding the technological advantages and disadvantages, thereby checking the theory with practice. And naturally, the conclusion will summarize the results of our findings as well as give our verdict on the SDRAM vs. RDRAM issue.



http://www.hardwarecentral.com/hardwarecentral/reviews/1787/
 
M

Moraelin

New Member
#2
Well, it is a whole lot better than the previous articles. At least it did show some benchmarks. And I should definitely start by saying: thanks.

However, it's not problem-free. For starters:

1) It is well known that the 4.20 drivers from VIA have serious performance issues. In fact, the AGP driver in those produces horribly low 3D performance, compared to the 4.17 ones. That's why VIA went back to offering the 4.17 ones, too. Why not try with those, too?

2) It's also well known that the 3.68 detonator drivers do not yet enable fast writes on VIA boards.

3) Also... why not use 2-2-2 SDRAM for the VIA board? Check it out, they ARE available. E.g., from Mushkin. (Yes, they are slightly more expensive than 3-2-2 DIMM's, but still a helluva lot cheaper than RDRAM.)

Briefly: what I see here is crippling the VIA board, to make the i820 and RDRAM show on top. At all cost.

4) Also... the fact that RIMM's are placed one after the other on the bus is good and fine. But it also means that latency increases when you add RIMM's on the bus. Yes, adding more memory on an i820 lowers your scores. Care to also show us what happens to those scores when you add more memory?

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Moraelin -- the proud member of the Idiots' Guild

[This message has been edited by Moraelin (edited 05-08-2000).]
 
M

Moraelin

New Member
#3
BTW, how about a comparison with DDR? I mean, ok, comparing RDRAM to SDR is good and fine, and interesting. But, well, all major manufacturers have announced DDR support already, and a lot of us have been holding off upgrades until DDR is here. It would be most useful to know what can we expect from it. Is it worth waiting for?

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Moraelin -- the proud member of the Idiots' Guild
 
B

bycustin

New Member
#4
First off do you work for Rambus or Intel?

You say you don't, but your actions are contrary to that!

The issue here is not that sdram is better than rdram. No one has ever said that. The price issue is part of all of this but you missed the point altogether, which this site seems to do a lot. Of course that happens when you have deadlines and advertisers to keep happy. Lets not argue trivial issues that we know that your right in this matter. RDRAM(PC800) is better than SDRAM(PC133), just 750% more expensive.

The issue we had before is your supporting of RDRAM as the next wave of ram. There are two new technologies on the horizon that have already implemented(in graphics cards), and those are:

DDR SDRAM and the much waited for QDR SDRAM
-You have heard of these right?


Compare your RDRAM to those and let us see what technology is cheaper and faster.
 
J

jsteimle

New Member
#5
I gave your benchmark results the quick once over and the BX look like its pretty close to the I820. Given the price differential I'd stick with the BX for the time being.
Jeff
 
P

penclboy

New Member
#6
I think this article was much better than lies, but I would like to see DDR done up with this type of in depth look. We are only a month or two away from DDR in MB's, ALL sorts of manufacturers are making chipsets for DDR; VIA, AMD, SiS, Ali, and even Micron is going to sell it's DDR chipset. I think this is a VERY strong group of manufacturers that can stand up to RAMBUS and Intel.
 
M

Moraelin

New Member
#7
Actually, penclboy, it's a lot worse than lies, because it presents some flawed data. What we have here is a competition where one of the competitors has been crippled.

E.g., it is well known that the 4.20 VIA drivers lower Quake frame rates by as much as 25-30%. It's been known for some months now. Yet guess which drivers are used in this benchmark? Yup, these slow ones.

With the proper drivers, the VIA board scores a bit better than either the BX at 100 MHz, and the i820 in most tests. And an 133 MHz BX spanks both the VIA and the i820 with Rambus. Despite running on that SDRAM which we're told is slow. Go figure. But then, showing that in a benchmark would put Rambus in a bad light, and we wouldn't want that


Basically, I'm not necessarily saying Sander is bought by Rambus. Maybe he isn't. Let's give him the benefit of the doubt. Maybe he's just totally clueless, and totally out of touch with drivers and performance issues


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Moraelin -- the proud member of the Idiots' Guild
 
R

RealityCheck

New Member
#8
"Splitting the control bus in this manner enhances transaction
pipelining by allowing a RAS operation for one transaction to be specified at the same time as a CAS
operation for a different transaction. Traditional technologies like SDRAMs require that Row and Column
addresses be transmitted on the same set of address lines, resulting in a resource conflict when the
memory system is placed under heavy load."

What? How can you address a row and column for different transactions at the same time? sounds like magic to me. Unless Gandalf designed the chips a RAS and CAS are needed for each unique memory address. To be able to assert them at the same time cuts out that particular latency problem. Of course if a DUAL channel rdram solution has its own full set of wires for each channel that would Almost make sense. Of course there goes the simplicity of design/low pin count for the mobo.


"The reason that this increase in bank count is
so important is that large increases in latency and decreases in bandwidth are caused by bank conflicts.
The larger bank count of RDRAM-based memory systems means that the probability of encountering a
bank conflict is smaller when using RDRAMs versus SDRAMs. "

What? Dont bank conflicts come into play when a series of memory address requests cross over from one bank to another? dont dont a small number of LARGE size banks of reduce the occurence rate this happening?
Doesn't a LARGE number of small banks Increase the occurence rate of this happening?

"Any new technology has lower yields than the incumbent
technology,"

Often correct but not universal. I.E. AMD's change over to .18 micron process and .18 copper process seems to have gone Flawlessly . When trying to push a new technology up against its limits right From the start is where many problems arise.




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A

adrianm2

New Member
#9
The article says that the fee paid to rambus
is around 2%. So from dell's website 256 meg
is $1340 and 2% = $28.

This is 17% of the price of 256 megs of sdram.

Ouch.

adrian
 
S

SnaggS

New Member
#10
Woops, I posted my reply as a newtopic by accident. Here it is in the proper place


-----

"a doubt that overall it does perform better than any other chipset currently on the market. "
Excuse me, it came last in 3 out of 4 Quake3 benchmarks. More importantly, how it performs at 640x480 is almost irrelevant, as this is not a resolution that will be used by people purchasing such a system.

Secondly VIA has long been known to have a worse implementation of AGP and memory than intel. What EVERYONE out in consumer land wants to know, is why doesnt intel just release a BX based chipset with ATA-66 and appropriate multipliers for the AGP/PCI bus when a FSB of 133 is used.

Toms hardware did a comparison of a BX chipset at 133, and it creamed the dualchannel rambus i840. For those interested in DDR vs Dual Rambus go; http://www.dccworkstation.com/htm/articles_0400/DDRvsDC_RDRAM_2.htm

So if your such an authority Sandra, please explain why a BX chipset at 133, without ATA-66, Hub Architecture or AGP 2.0 can outperform the top of the line i840 chipset?
 
B

bdwilcox1

New Member
#11
Sander,

Van Smith of Tom's Hardware gave full disclosure concerning any possible holdings he may have relating to Rambus or DDR-SDRAM. (BTW, he didn't have any.) I believe you should do the same if you wish to maintain credibility.

Speaking of full disclosure, I find it highly suspect that you chose BAPCO's SysMark 2000 as the standard benchmark, considering that Intel partially owns BAPCO. Proof resides here. As such, I'm sure Intel highly optimized this benchmark for Intel platforms, most notably the one they're currently trying to foist onto the buying public.

Considering that rather mature DDR-SDRAM platforms exist, with reference boards available from Micron, it also casts doubt on the fairness of your Rambus assessment. Hey, look, this Camaro beats a model T, so it definitely is tomorrow's vehicle! Of course the comparison suspiciously leaves out the Corvette as one of the contenders.

If you want to play with the big boys in this arena, you better be more thorough and fair-handed than you have with this poor showing. Shame, really.

-Brian Wilcox
 
B

BLewey

New Member
#12
Two things not accounted for in this article: the size of the A pool in the i820 chipset and the "adjacent open" limit of Rambus' design.

Much of the information I state was originally published by Paul DeMone, of www.realworldtech.com on this article http://www.realworldtech.com/page.cfm?ArticleID=RWT112299000000 (go to the fourth page).

1. The 820 supports a maximum of 8 open pages across all DRDRAMs in the system. If the desired Rimm is not one of those eight (and there are 128 in an 8 device Rimm), there is an additional 40-50ns wait for the chip to become active. Any program requesting data spread across multiple Rimms will encounter this delay. In some applications this is insignificant, in others, it can allow even PC100 SDRAM to outperform DRDRAM.

2. Mentioned in both aticles is the fact that adjacent pages cannot be simultaneously open. At first this seems not important considering only eight pages can be open on the i820; but, first, it would matter in future motherboard designs that could have more open pages (much greater power consuption, however). Second, reading from a small group of adjacent Rimms will require frequent switching of active Rimms because of the this limitation. For example, if data is being randomly accessed from adjacent Rimms, there would be a 50% chance that a data access would require retiring/waking up Rimms.

Though I still prefer DDRRAM, it was interesting to see an article pointing out the advantages of DRDRAM. The memory battle in the next few years will be interesting.
 
M

Moraelin

New Member
#13
Well, on the theory side he did keep all the omissions and hype from the previous article. What can I say, at least he's consistent


E.g., interesting to note how when talking about the latencies of RDRAM he fails to mention the effects of taking a nap for thermal reasons. What makes this omission even more interesting is that he mentions only the active chip as dissipating 4W, which makes me think the others on the stick are taking a nap. (Either for inactivity or for thermal reasons.) And he does mention the need to spread that heat around, via that flat heatsink. Yet I don't see anywhere a mention of the time penalty for waking up such a chip to active state.

E.g., he fails to notice that while RDRAM does work with fewer traces on the motherboard, those traces operate at a much higher frequency. Hence, trace length and interference problems are much bigger for the manufacturer. Hence, that motherboard won't really be any less expensive. Add the more complicated chipset, and the mobo is actually more expensive.

Etc, etc, etc. But then, as I've said before, I'm more interested in benchmarks than in that hype anyway. Assuming he can ever bring himself to do them right


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Moraelin -- the proud member of the Idiots' Guild
 
X

xtreme

New Member
#14
well it has been proven that RDRAM isn't as good as ppl think...

i guess it all comes down to how intel and rambus market the product

anyway i just wonder how much $ the RDRAM guys paid this site to do such a review

POINTING out the Advantage of RAMBUS, but also pointing out the disadvantage of SDRAM

if u guys wana be fair, RUN everything at the 133mhz level and you will see how SDRAM and the BX kicks...

duno why u guys use 3-2-2 PC133 also

i guess u guys should try using PC600/700 RDRAM also

btw.. also never mention a word of DDR


[This message has been edited by xtreme (edited 05-09-2000).]
 
J

Jawz

New Member
#15
You are very quick to point out deficiencies in the SDRAM design but fail to do the same for RDRAM. I guess RDRAM's deficiencies have been thoroughly aired by other sites though, so fair's fair.
One thought though. In a modern general purpose computer design, many of the deficiencies of the underlying system memory are hidden by the processor cache are they not? So whereas RDRAM may be the ideal solution for the Sony Playstation for a variety of reasons, system designs based on the Pentium III (Celeron incl.) and Athlon may be less fussed.
 
S

Sander Sassen

New Member
#16
Hello there,

I'm really suprised that most of you are suggesting that I or even HWC is 'owned' by either Rambus or Intel. Allow me to fill you in on some of the work that has gone into writing this article. Most of the info you'll see posted came from Rambus, Intel, Samsung, Micron, VIA and AMD a whole slew of company datasheets and a compilation of other websites' data.

I've asked each and every one of these manufacturers to send me a package with some indepth technical background info, which I them compiled into the info you see posted. I think I've done a fair comparison by all means, all the drivers and benchmarks used were recommended to me by the manufacturers of the applicable chipset/motherboard/manufacturer, you can be sure that they make sure I use a driver/benchmark that has their product performing at best.

One of the things that really offends me with these kind of flames is the fact that you people tend to absorb all anti-Rambus/Intel articles as the word of God, but flame one that does shed a different light and dares to take a different point of view. Who's being objective here? I disclose all info, drivers used, benchmarks etc. I don't see any of that in those other 'articles', they just summarize their results without posting a single screenshot and you tell me you're buying that?

I don't own any Intel or Rambus stock, nor any stock for that matter. I don't get company kickbacks, or get whatever CPU + memory I want for personal pleasure for free. I think you should think twice before you start making these kind of claims.

I hold a masters degree in EE and a bachelors in ME, so you can be sure I'm able to tackle any technical issues, thus I might not do the benchmarks you'd like to see, I do however make sure they're objective and as well documented as possible, the same cannot be said about many others.

I'm all for constructive critisism, but come up with valid arguments and support them with a link, a quote, etc, don't just state that I did a bad job, as that is soo easy. To quote some of your own statements; 'If you want to play with the big boys in this arena, you better be more thorough and fair-handed than you have with this poor showing. Shame, really.'

Thanks and best regards,

Sander Sassen
Siteleader at HardwareCentral
Email: [email protected]
Visit us at : http://www.hardwarecentral.com
 
D

Dexter

New Member
#17
First of all, it IS easy to flame, but then I'd say, when you flame do so in style. (Do it with facts).
Personally I welcome this article, it shows RDRAM in another light. But as others allready pointed out, it is clear in pointing out the merits of RDRam versus the 'bad' things in SDRam. And I am missing the 'bad' things of RDRam, cauz when it's that good, why does it fail to outperform SDRam ?


My it is because your used sources did hide this information from you ?

Also I'd rather see a comparison of RDRam vs. DDRam. Since there almost 'equal' in age
and and have a similair bandwidth. Micron itself has allready stated that allthough the bandwidth of the newest types of DDRam is higher, due to it's less efficient protocol it approaches that of RDRam. (Sorry no link for support)

Then again (dunno where I read it but) this might be one of those attempts of Intel to seize control over the (pc)world again.

For a personal note...I keep saying this is a smelly kinda memory.

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driesens.com
 
D

Dexter

New Member
#18
First of all, it IS easy to flame, but then I'd say, when you flame do so in style. (Do it with facts).
Personally I welcome this article, it shows RDRAM in another light. But as others allready pointed out, it is clear in pointing out the merits of RDRam versus the 'bad' things in SDRam. And I am missing the 'bad' things of RDRam, cauz when it's that good, why does it fail to outperform SDRam ?


My it is because your used sources did hide this information from you ?

Also I'd rather see a comparison of RDRam vs. DDRam. Since there almost 'equal' in age
and and have a similair bandwidth. Micron itself has allready stated that allthough the bandwidth of the newest types of DDRam is higher, due to it's less efficient protocol it approaches that of RDRam. (Sorry no link for support)

Then again (dunno where I read it but) this might be one of those attempts of Intel to seize control over the (pc)world again.

For a personal note...I keep saying this is a smelly kinda memory.

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driesens.com
 
M

Moraelin

New Member
#19
I don't know, Sander... Claiming that everyone else doesn't give the details is a bit of a stretch.

Granted, some sites do an even poorer job at benchmarking. And in all fairness, this hapens on both sides of the debate. I won't deny that. But then, I won't consider them to be professional, either.

On the other hand, there are enough sites out there that do a very thorough job about it. As in: running a lot more benchmarks, under NT, Windows 98 and Windows 2000, and experimenting with the drivers to see what happens.

It's precisely this second kind of test I'm interested in. Precisely BECAUSE it's a lot of work, and I really don't have the time (nor the funds) to do it myself. Frankly, if I wanted to settle for Sandra and Quake, with whatever OS and drivers happen to be installed, I'd just go to a friend's house and run those myself.

But what I'm really interested in os that someone did a helluva lot of work tweaking and testing, so I don't have to do that myself.

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Moraelin -- the proud member of the Idiots' Guild
 
stribe

stribe

New Member
#20
Moraelin et al:

To be fair to Sander: I've not seen anyone do a comparison of DDR-SDRAM to RDRAM anywhere online yet - tho in the same breath, I will say that every other site thats done RDRAM vs SDRAM comparisons does mention the DDR-SDRAM in depth, and I've not seen that in either of the 2 articles that Sander has posted. I can excuse that I suppose by giving him the benefit of the doubt on that he is looking at current technology and whats available now.. not on whats going to be available. However, i do find it interesting that this is one of the few sites out there (actually.. the only one I've seen) that continues to insist that RDRAM is the "2nd Coming" (other then Rambus of course)

More interesting in light that I've seen news articles in recent days that a couple of memory manufacturers are cutting back on RDRAM production because of poor yields and because most anticipate not having a very big market for RDRAM - focusing instead on the perceived more lucrative SDRAM market (or DDR-SDRAM market). There are also hints that Intel may be backing away from RDRAM and is starting to make sure a lot of its platforms are SDRAM compatible. So Sander, while I admire you and your site for trying to educate the masses, I'd say your conjecture that RDRAM is the next best thing to happen to the PC world is debatable at best.
 

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