RD RAM, pc1066 questions

[dmitriyaz]

with the pc1066 out, there is lots of confusion (in my head, that is).
if any of you know answers to any of the following questions, please post.
also, any other questions about RD-RAM, post them too

here is the difference between DDR and RD RAM:

DDR (pc2700, as an example):

(166 MHz Operating Speed) x
(2x Rising & Falling) x
(64-bit Bus)
/ (8 bits per byte) = 2656 MB/s available bandwidth.

RDRAM (pc800):

(400MHz Operating Speed) x
(16-bit Bus) x
(2 Rising & Falling Edge)
/ (8 bits per byte) = 1600MB/s available bandwidth.

RD RAM (the new pc1066)

(533 MHz Operating Speed) x
(32--(note, its twice bigger than the previous RD RAM) -bit Bus) x
(2 Rising & Falling Edge)
/ (8 bits per byte) = whopping 4200 MB/s available bandwidth.
that, my friends, is 1000 mb/s more than the upcoming ddr400

so here are the questions:

1) when you upp the FSB, does your RDRAM's frequency go up too? with what rate?
2) how do they like extra voltage?
3) the bandwidth of pc1066 is 4.2 gb/s, and the i850e (intel 850e is the only chipset that supports pc1066) memory controller bandwidth is only limited to to 3.2 gb/s; why?
4) %-wise, how well does RD RAM overclock?
5) is pc1066 backward-compatible with pc800?
6) for a low end Northwood (1.6a) setup, if you plan to overclock to the max, is pc1066 worth it?
7) if you use a 400mhz fsb northwood, can you still make your ram operate at 533mhz (pc1066) ? (asyncroniously, that is...)
8) will pc1066 still run at 32 bit (instead of pc800's 16 bit) if you are running it at pc800 speeds?
9) whats the deal with the single/dual channel? do i need a special motherboard so support dual channel? does pc1066 have 32 bit bus and pc800--16 bit bus because one is dual and the second one is single channel?

thanks,

[Charles Wirth]

1. P4A 100Mhz FSB, raise the FSB 10Mhz to 110FSB the memory will be running at 110x4 or 440Mhz.
P4B 133FSBx4=533Mhz, now raise the FSB 10Mhz to 143Mhz the memory will be running at 572Mhz
You can change the 4x ratio from 4x to 3x to reduce the Mhz on the ram if FSB is too high for RDRAM at 4x
P4A @ 170FSBx4=680Mhz, this is very hard on PC800 so you would use 3x ratio in BIOS to get 510Mhz

Ok, from the information above you can quickly estimate PC rating with the following equation and don't forget if you changed the RDRAM ratio to change the equation.

100Mhz FSB x4 = 400Mhz RDRAM x2 = PC800
133Mhz FSB x4 = 533Mhz RDRAM x2 = PC1066
150Mhz FSB x4 = 600Mhz RDRAM x2 = PC1200

2. You can give the P4 lots of vcore voltage as long as you have the cooling to back it up. Try for best overclock without going to vcore. once you figured out what does what and have temps under control you can go nuts with vcore. Just remember to keep temps under control with good circulation and aftermarket HSF if you plan to go big.

3. I was unaware that it was limited, you are overclocking right?

4. PC800-45 is good for about PC1066 speeds but not always
PC800-40 is good for PC1066 speeds and PC1200 is possible.
PC1066-35 PC1066 guaranteed, PC1200 should be pretty easy
PC1066-32 is the best, PC1200 speeds guaranteed and PC1400 is possible.

My numbers are not set in stone but should be pretty close.

5. Yes and no, I have not seen a compatibility list yet, but there are some issues with PC1066 on some I850 boards. You can run PC800 on any I850e board. It is recommended that you run PC800-40 on I850 for guaranteed compatibility. There is a way to trick a I850 board into firing up with PC1066 installed. Can anyone confirm PC1066 is running at CAS3 over 411Mhz on I850?

6. Well, what is your budget? what features do you want? If you get a I850 board use PC800-40, If you get a I850E board get PC1066-32, you can run the PC800-40 @ 133FSB without any problems on the I850E. just remember the CAS2-2 to 411Mhz on PC800-40

7. I cannot confirm any I850E mobo can do the requested, you would have to OC the processor too to get the 133FSB. If anyone can confirm, please do.

8. Toms Hardware has a review of six I850E boards and explains the 32bit RDR on the Asus P4T533 32bit RDRAM support.

9. see #8

Any corrections welcome,

[Coolzero2k1]

PC800-45 is good for about PC1066 speeds but not always PC800-40 is good for PC1066 speeds and PC1200 is possible PC1066-35 PC1066 guaranteed, PC1200 should be pretty easy
PC1066-32 is the best, PC1200 speeds guaranteed and PC1400 is possible

I do not yet have any experiences with 32/35 ns rambus because here in germany they are hard to get! But my experiences with 40ns rambus were not very good! I'm selling P4 overclocking sets here in germany and so i had many possibilitys to test a lot of p4 steppings, motherboards and Memory-Modules but i could clock pc800/45ns higher then pc800/40!

The best pc800/45 modules are samsung 128mb/4!
I could clock them over 1100mhz!

There is a trick how you can clock rambus more! Over a voltage of 2.65V the ram is produsing more failures and so you canniot clock it so high!I talked with a friend wich works @a memory factory and he gave me a Tipp, you should set the voltage of the rams to 2.4 or even 2.35V on this voltage you can overclock the modules higher than at voltages over 2.5V! But you should not go under 2.35V because then your system will not run stable!

I hope I helped you, and i'm sorry for my bad englisch!

Cya Coolzero

[Charles Wirth]

I have not found a PC800-40 that could not reach PC1200/150x4 speeds. Even the Kingston value ram does 150x4.

It might be your motherboard limiting you.

[Coolzero2k1]

What motherboard do you youse and on wich voltage have your memory reached 1200???

[macci]

Originally posted by dmitriyaz

RDRAM (pc800):

(400MHz Operating Speed) x
(16-bit Bus) x
(2 Rising & Falling Edge)
/ (8 bits per byte) = 1600MB/s available bandwidth.

You forgot one thing. Its dualchannel so the available bandwidth is 3200MB/s (2 x 1600)

RD RAM (the new pc1066)

(533 MHz Operating Speed) x
(32--(note, its twice bigger than the previous RD RAM) -bit Bus) x
(2 Rising & Falling Edge)
/ (8 bits per byte) = whopping 4200 MB/s available bandwidth.

THat 32bit stuff would be the new RIMM4200 (not PC1066 - although performance wise its pretty much excatly the same thing )

PC1066 would be:
(533MHz Operating Speed) x
(16-bit Bus) x
(2 Rising & Falling Edge)
/ (8 bits per byte) x 2 channel = 4200MB/s

3) the bandwidth of pc1066 is 4.2 gb/s, and the i850e (intel 850e is the only chipset that supports pc1066) memory controller bandwidth is only limited to to 3.2 gb/s; why?

Thats because the I850E doesn't OFFICALLY support PC1066 (although most of the i850E mobos do.. :P) its designed to run at 133MHz 3x RDRAM (=3.2GB/s)
Obvioulsy the second you set the RDRAM mode to 4x @133MHz FSB (in the mobo BIOS) you have overcome the limitation

7) if you use a 400mhz fsb northwood, can you still make your ram operate at 533mhz (pc1066) ? (asyncroniously, that is...)

AFAIK thats not possible.

PC1066-32 is the best, PC1200 speeds guaranteed and PC1400 is possible

Only PC1066 speed is guaranteed w/ that stuff. I've tested couple of those (both samsung -32 and kingston pc1066 (not sure if it was -32 though) and 2 out of 3 couldn't not run 100% stable at 150 4x using the default voltage. Things may change in the future though (atleast I hope so!)

The best pc800/45 modules are samsung 128mb/4!
I could clock them over 1100mhz!

Well you have been very lucky w/ that stuff cos its a known fact that 128/4 (64/2 and 256/8) samsungs are the worst overclockers :P
btw my samsung 128/8 -45 doing near 1300MHz (in a warm room - might do more w/ some cooling..)

16bit => 2 x RDRAM modules (or 4 x) and 2 x RDRAM terminators (aka C-Rimms) (or if using 4 modules then the terminators are not needed)
32bit => 1 x RDRAM modules (or 2x) and 1 x RDRAM terminators (or if using 2 modules then the terminators are not needed)

16bit mobo = 4 RIMM slots
32bit mobo = 2 RIMM slots

[Coolzero2k1]

Are you sure? I have tested the 128mb/8 too, but i couldn't overclock it higher than the 128mb/4!
I think my Abit TH 7 II hav some probs with high memory frequences! What other boards are there with a pci/agp fix and which have no probs with high frequences??

[dmitriyaz]

hmm...
thanks guys,
a quick quesion:
when people OC athlon XP mobos to 200 fsb, they only OC the pc2700 by 20% or so,
when ppl OC their 1.6a based mobos to 170 fsb, that like 70% overclock on RD RAM memory!
is that real? an i missing something?

[macci]

when ppl OC their 1.6a based mobos to 170 fsb, that like 70% overclock on RD RAM memory!
is that real? an i missing something?

at FSBs of 150 and up people usually set the RDRAM to 3x mode. so at 170fSB it would be 170 x 3 = 510MHz (PC1020)
That is about as fast as running 130 4x RDRAM

[macci]

The highest (somewhat stable) RDRAM overclock is around 175MHz 4X (=PC1400) mode though but that requires some very insane cooling methdos (=subzero temps for RDRAM) and voltage modifications.

[dmitriyaz]

i see...
what exactly kind of voltage mods are you talking about?

[macci]

mainly Vmem (RDRAM voltage - 2.5V stock) modifications and maybe I/O (3.3V) voltage increase too.
Incerasing those voltages usually gives a little boost in RDRAM speed [depening on mobo and DRCGs (= Rambus clock generators on the mobo)].

But long term RDRAM overvoltage can kill or weaken the overclockability of the RAM

[dmitriyaz]

just curious, %-wise, what is considered a "little boost" and what--"overvoltage"???
thanks macci, and all the others, you guys are great

[Charles Wirth]

I have not needed to increase my memory voltage on RDR, I have tested many boards and ram modules over the passed 6 months.

Only PC1066 speed is guaranteed w/ that stuff. I've tested couple of those (both samsung -32 and kingston pc1066 (not sure if it was -32 though) and 2 out of 3 couldn't not run 100% stable at 150 4x using the default voltage. Things may change in the future though (atleast I hope so!)

To my understanding the PC1066-32 is made to operate at PC1200 speeds. and the PC1066-35 is true PC1066 (kinda like PC800-45 vs PC800-40) even tho it is not official it fits the spec.

I must have beed getting good ram, I am yet to find any that will not run at 150x4 in the current batches. I found that my Mobo was my weakest link.

I have sandra's from over the passed 6 months if you like to pick thru them. let me know to link them up and I will. P4T-E and TH7-IIR.

I have the above systems still if you want me to show you new bench at above clock speeds.

[dmitriyaz]

when you say your mobo was the weakest link--are you talking about abit??? seems unlikely...?

[CSHawkeye81]

you cant say abit has made everything great, you might just have one of those weird boards it sucks cause a guy at the hardforums went through 4 boards until he got his 1066 to run stable.

[dmitriyaz]

hmm...
but abit are the only ones that have the "fixed divides" feature, isnt it?

[CSHawkeye81]

yeah mostly a couple epox's use it as well.

[dmitriyaz]

interesting...
say in a mobo, you have 2 sets of 2 rambus slots, total = 4;
--if i have 1 module, do i need 3 dummies (c rimms) or only 1, for the slot next to it?
--also, will it still be 32-bit and not 16-bit if i istall one module and a dummy?
--and, if the answer to that one is "yes", what is generally better for overclocking using 1 or 2 modules?

[macci]

32bit RDRAM module is basically 2x16bit RDRAM modules ("two-in-one").

And if you have a mobo w/ 4 slots its a 16bit mobo and you need to install 2 or 4 RDRAM modules (1 or 3 won't work)

I guess I need to quote myself

16bit => 2 x RDRAM modules (or 4 x) and 2 x RDRAM terminators (aka C-Rimms) (or if using 4 modules then the terminators are not needed)
32bit => 1 x RDRAM modules (or 2x) and 1 x RDRAM terminators (or if using 2 modules then the terminators are not needed)

16bit mobo = 4 RIMM slots
32bit mobo = 2 RIMM slots

[dmitriyaz]

hmm...thats a whole damn lot of terminators...
sorry for not paying attention, that was a very good explanation

[macci]

Originally posted by FUGGER
To my understanding the PC1066-32 is made to operate at PC1200 speeds. and the PC1066-35 is true PC1066 (kinda like PC800-45 vs PC800-40) even tho it is not official it fits the spec.

I must have beed getting good ram, I am yet to find any that will not run at 150x4 in the current batches. I found that my Mobo was my weakest link.

It was also my understanding that the -32 stuff would run easily at 150x4 unfortunately that hasn't been the case w/ the RAM I've tested. Overall the kingston pc1066 (some of those hit a bit over 150) seems to be doing better than the samsung I've tested.
I also found that I was able to overclock a bit higher on P4T-E (w/ 600MHz DRCGs) than on TH7-2.
Out of curiosity.. what kind of modules (64,128..) have u tested and whats the highest "3D stable" or Sandramem stable speed you have hit?

[dmitriyaz]

abit has the fixed dividers, and that is the only way to go if you have 1.6a and wanna push it to 2.5 or more. so how is abit th7-2 anyway?

[Charles Wirth]

Here is a few boards of mine while I was noting differences in the generations. My best board shown has the chopped Ultra750 ramsinks on the DRCG's, also my oldest board.

Kingston PC800-40 256MB

Samsung PC800-40 128MB

Samsung 151x4 temps and stuff

Samsung PC800-45 256MB 150x4 or 170x3 capable

Samsung PC800-45 128MB 150x4 or 170x3 capable

Filling all the memory slots 2GB, no problems of any kind were found.

All the above SS were taken from Sandra on a TH7-IIR or a Asus P4T-E. Complete sandras available on request.

I love my IT7 more! oops...

[dmitriyaz]

why do do you like your IT7 more? its DDR! i thought rd ram was suppoesd to be faster
in any way, how do you feel about th7II? is it the best board to go with? considering i need the fixed dividers