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Latency or Bandwidth more important?

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September 8, 2002 4:56:12 AM

I've seen lots of reviews of PC2700 and PC3200 DDR SDRAM.
Most PC3200 DDR SDRAM is at CAS2.5 except for Corsair that I know which has CAS2 PC3200 DDR ram. However just looking at "Changing Of The Guard: Four Athlon Motherboards For DDR400" review here on Tomshardware it seemed to be as if the chipset was more important than the memory itself. So really I'm wondering what's the best DDR RAM I can get on the market right now? Out of all the reviews I've seen even when using practically identical settings and timings one was eventually better than the other depending on which company the ram was from.

I'm intending to overclock as much as possible and wanting stability so is Corsair still the king?
And am I better off with PC2700 since there's chipsets that offically support it or PC3200 all the way?
Not sure but was PC3200 part of the JEDEC standard?
Oh yes just to let you know I'm on a Intel based system.
And will be getting the P4S8X very soon so SIS 648 chipset.

Thanks.
September 11, 2002 1:20:02 AM

1 only 1 dimm can be use alos to reach stability you need to raise the voltage for the dimm
2 Jedec dont support DDR 400
3 anandtech was not able to run DDR400 with any P4 chipset it can run on a athlon manly because the bandwith got wasted
4 personaly it a waste of money atlease PC2100 was stable.

At the end i have speak with a horny lady
September 11, 2002 2:03:14 AM

On a side-note, latency is often the most important. Notice, RDRAM at 3.2GB/sec gets killed by 2.7GB/sec DDR, solely because latency affected the bandwidth efficiency. So DDR 400 would almost rape the PC800 RDRAM. Dual Channel DDR will also have even more significant latency reductions and its high bandwidth would be perfect for P4s, with low latency.

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September 11, 2002 3:28:56 AM

Yes I plan on only using 1 DIMM for obvious reasons..
Take a look here on Tomshardware, on the mainboard guide "DDR400 Kills Rambus: Shooting Star SiS 648 for P4".
I'm talking about the SIS chipset not Intel..
September 11, 2002 3:37:48 AM

Hmm okay. Well dual DDR is supposedly coming out sometime mid next year but not sure on that. Yeah I also think it'll take over RAMBUS when dual channel DDR hits the market because of their lower costs over RAMBUS. But would you have any idea if you'd need special DDR RAM DIMMs for a dual channel setup or should the ones we buy today work perfectly fine on a dual channel ddr platform?
September 11, 2002 8:49:26 PM

No you only need normal DDR sticks, nothing special. RDRAM was designed serial to work in Dual Channel, so only RIMM4200 can possibly run Single Channel at Dual Channel bandwidth.

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September 12, 2002 12:51:23 AM

Alright. Basically when Dual DDR comes out it would basically kill RAMBUS then wouldn't it? Nothing really special with RIMM4200 other than it can run in a dual channel bandwidth by itself but no performance boost.. On the other hand when Dual DDR comes out you'd be only having a latency of 2.5 if both pieces of DDR RAM are CL2 compared to two pieces of RDRAM which has a cas latency of like 5 or something...
September 12, 2002 10:04:20 PM

I thought dual channel ddr was going to be it. But then I'm hearing quad channel rdram. So quad channel rdram should be doing like 8gigs of bandwith or somewhere around that.
September 13, 2002 1:33:39 AM

Raystonn, an Intel engineer who used to hang in the CPU forum, had stated how as RDRAM's clock goes up, the latency becomes far less, that at some point it is superior to DDR's latency, as in less.

Typically, yes, if all is well, Dual DDR would definitly kick ass, but unfortunatly it has not been seen since, and SiS is often the company we would look at for pushing it one before Intel's chipsets. I would like PC2700 Dual Channeled, so you get 5.4GB/sec with low latency, something the P4 would easily go for.
However if it's true about the QDR RDRAM coming soon, (lol, with Rambus that means 2005) with its high speed it should gain low latency and MAJOR bandwidth so indeed it could be the future memory choice. DDR II is only an upgrade, so if you do not innovate your RAM, you can only go so far. Perhaps people have misjudged Rambus a lot like they misjudged the first P4s as the future of crap.

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Anonymous
a b } Memory
September 13, 2002 2:36:22 AM

the channelness is in the controller design not in the memory design. It would be up to the chipset makers to make a quad channel controller rather than a memory manufaturer.

For example remember the i820 and i840 chipsets from Intel? The i820 was single channel and the i840 was dual channel, but they could both use the same type of memory modules.
September 13, 2002 5:11:47 AM

Hmm true but I'm not going to bother with it. Haha it'll actually be quite interesting how it turns out in 2005 but I doubt it's going to go back mainstream. I mean just look at the pricing. Plus not sure if it will attract any overclockers as RDRAM does get VERY HOT. But who knows. The SIS 648 is coming really close with RDRAM already and it's only on a single channel. Just going to have to wait and see I guess. Hmm can't see why people would say P4s will be crap in the future. I mean at least they have a heatspreader on it to protect the actual core from chipping unlike the Athlon XPs where you can chip it easily and kill the CPU..
September 13, 2002 7:22:46 PM

I was referring to the fact Intel is slow at making the new technology be used. Look at how i850E came out with supporting a superior FSB but not the superior RAM. That IMO is a very flawed move by them. PC1066 IS designed for 133MHZ QDR FSB, and why they took time to validate it, is beyond me. Perhaps this is why RDRAM PC1066 is not available anywhere.

SiS on the other hand, or even Nvidia and VIA, can push stuff event though the CPU maker didn't want or need. I hope SiS will budge soon and get that Dual DDR chipset, it's a much needed test, and I know Intel will just release one too late (just like DDR333MHZ validation and even DDR P4 chipsets), as well as make it validated for the outdated PC2100. If they tried PC2700, I'd change my stand on their actions in this case.

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September 13, 2002 7:46:01 PM

both are equally important. This is just an experiement. Seeing if it works.

What i'm doin is [mhzxbytes) - ((mhzxbytes)*latency)] to get the actual performance. pc3200 does not take into account the latency. And the above formula would include latency within the pc rating.

[(400 * 8) - (400 * 8 * 0.30)]
3200 - 960 = 2240

pc3200 at cas 3 = 2240
pc3200 at cas 2.5 = 2400
pc3200 at cas 2 = 2560
pc3000 at cas 2.5 = 2250
pc3000 at cas 2 = 2400
pc2700 at cas 2 = 2160
pc2700 at cas 2.5 = 2025
pc133(pc1064) at cas 3 = 744.80
pc133(pc1064) at cas 2 = 851.20
pc100(pc800) at cas 3 = 560
pc100(pc800) at cas 2 = 640

*shrugs* it's just an idea i had flowing in my head.


<A HREF="http://www.anandtech.com/mysystemrig.html?id=9933" target="_new"> My Rig </A>
September 13, 2002 9:03:29 PM

"However if it's true about the QDR RDRAM coming soon, (lol, with Rambus that means 2005) with its high speed it should gain low latency and MAJOR bandwidth so indeed it could be the future memory choice."

Do you happen to have a link for that?

All I have ever seen was "Yellowstone" which is <A HREF="http://www.rambus.com/about/pressreleases_2002/020708.s..." target="_new">ODR - Octal Data Rate</A>. But they even said that that wouldn't be used for main memory systems. So if there is a QDR version of RDRAM I would like to read up on it.

<b>"If I melt dry ice in a bathtub, can I take a bath without getting wet?" - Steven Wright</b>
September 14, 2002 9:01:20 PM

My bad, I got confused here.

But I thought there were QDR and ODR?
I mean if 8GB/sec is expected soon from RDRAM, then isn't that QDR RDRAM?
ODR would have it go twice further, so I do beleive there is QDR, a lot have been speaking about it recently. ODR is too far however, I mean think of the costs!

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September 15, 2002 3:26:08 AM

Anadtech benchmark show that any chipset of all kind any mobo was unstable with PC3200 Jedec dont want to support it because it unstable.On the same article show that PC1066 is untouche able DDR was a tempory solution because Jedec was not able to anchor a deal with rambus even DDR-3 will still be slower that RDRAM.SDRAM is dead it soly live because most of power useur choice there hardware for political reason and not from a tecnical point of view.

Radeon 8500 AMD DDR Linux as long the compagnie look like a under dog it ok to buy

At the end i have speak with a horny lady
September 18, 2002 8:20:48 PM

Hum... excuse me juin, but I dont think that every power user out there is so much filled with bucks that he will pay twice the price of a DDR stick for the same performance. OK, RDRAM is ahead DDR, but in most cases, you will get VERY satisfying results with DDR, usually 10% under RDRAM. So why the hell would I pay more for the same thing ??
There is no political choice there, just a choice no to waste money, thats all
September 18, 2002 10:10:50 PM

Hum... excuse me juin, but I dont think that every power user out there is so much filled with bucks that he will pay twice the price of a DDR stick for the same performance. OK, RDRAM is ahead DDR, but in most cases, you will get VERY satisfying results with DDR, usually 10% under RDRAM. So why the hell would I pay more for the same thing ??
There is no political choice there, just a choice no to waste money, thats all


It far from 10% to come close to RDRAM you need very good DDR 2700 best timing also only 1 dimm must be use that a choice you got all chipset reduce speed of DDR 2700 to PC 2100 even 3 dimm or more are use.It ustable slow and anti-R&D.RDRAM is also a much better overclocker and also scale with more mghz unlike many componant.It cost only abiout 20$ per stick more that not much.I am aware that in autralia canada Pc1066 cost huge amount more that DDR but in us that not the case.That like P4T533 cost more that any boards and have 1 of the lowest production price anything relate to RDRAM have a very good margin of profit.

At the end i have speak with a horny lady
October 20, 2002 5:22:03 PM

Dragged this ne back up cos it's very interesting (to me at least :smile: ).

How about PC3500 CAS 2?

(433 * 8) - (433 * 8 * 2)
3464 - 692.8 = 2771.2

Is that it?

<b><font color=blue>~ <A HREF="http://www.btvillarin.com/phpBB/viewtopic.php?t=324" target="_new">My System Specs</A> ~<font color=blue></b> :wink:
October 20, 2002 7:14:04 PM

Is there a way to identify if the memory is CAS2 and not CAS2.5? Let's say a person trying to sell me PC2700 512 CAS2 Corsair. I do I know that it is CAS2 and not CAS2.5? How do I know if he's trying to rip me off?
October 20, 2002 7:46:15 PM

So indeed CAS latency helps getting closer to the real theoretical bandwidth performance. My god if RDRAM at 3.2GB only gets about 2.2GBs peak, the P4 is seriously hampered by latencies!

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October 22, 2002 6:34:32 AM

Yes.
Why do you think PC2700 with hard memory timings is almost equalling PC800?

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