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9 Questions on RAM

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June 9, 2003 7:36:06 PM

Here are some questions that for some reason or another I dont know the exact answer to and would love some clarification, thanks:
1) What is the advantage of 2 RAM chips over 1 of comprable speed (ie. 2x 256 or 1x 512)?
2) What does the PC____ refer to (ie PC 3200)?
3) How does one synch one's cpu and RAM? (In my case I have a 1.8 with 100 OC to 133 making it a 2.2, my RAM is DDR333 PC 2700. What is the best combination of speeds, and if I wanted to OC more what is the best combo?)
4) Can I have two different types (PC2700 and PC3200) of RAM on the same mobo?
5) Can one alter one's RAM speeds or anything to do with RAM?
6) Why are some RAM much better then others despite having the same PC___ and DDR___?
7) What is the best RAM and why?
8) What is bottlenecking?
9) Please give me the best settings for my 1.8 (100x1.8) and my 1x 512MB DDR333 PC2700... Do I need more RAM and how far can I OC and not 'bottleneck'?

Thanks for any help you guys can offer.

-Asus P4S533 mobo

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June 10, 2003 12:46:37 AM

1) sometimes it can be cheaper to ge two sticks as oppsoed to one, but if your motherboard supports dual channel memory then there is a huge advantage to having 2 sticks
2)it refers to the speed of the memory i think (ie. pc2700 is ddr333, while pc3200 is ddr400)
3)you need to sync the fsb of you cpu to your ram (ie. fsb = 333 to sync get pc2700 ram with ddr333)
4)i think you can but im not positive on this one. It depends on if your mobo can support it or not. say you have pc2100 in your mobo and slap in a stick of pc2700 well i htink the pc2700 should dumb itslef down to pc2100 speed
5)yes with overclocking you can, you can do it in bios and with some other programs, but im not big on overclocking so i couldn't tell you which ones.
6)they aren't. pc2700 runs faster in most cases that pc3200 would run. its all about syncing the cpu and ram speed. basically if your cpu fsb is 333 there's no point in upgrading to pc3200 with ddr400. sorta a scam for the people who dont know htis tho, but thats marketing for ya.
7)the best ram depends on whay type of motherboard and cpu you have. the best companies that i personally think are best are corsair, samsung, crucial, and kingston
8)bottlenecking i believe is a term used with overclocking - dont know much about it
9)im not too familiar with intel mobos so i couldn't tell you what the best ram for you is. I can tell you that it is unlikely you would need more than 512mb ram unless you are running some memory demanding programs or something.
Hope his helps.
June 10, 2003 1:15:16 AM

Thanks for taking the time answer all these questions :p  It clears some up but the main point that still confuses me is:
My computer normall runs at 100FSB, and right now is OC to 133... how in gosh names would I ever reach 333 or 400? I am sure you can't with a 18x multiplyer so my question is am I supposed to reach half, ie. 166FSB for DDR333 or 200FSB for DDR400? Even then 166 would make my comp almost 3.0, a large upgrade from 1.8, so I am still confused... Also what is dual channel memory and how do I know if I can use it? Thanks for any help you could give.
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June 10, 2003 2:00:19 AM

3) Most higher memory modules are reverse compatible.


<font color=blue>/Next time there is a war in Europe- the loser gets stuck with France this time.</font color=blue> Support your troops!!!!
June 10, 2003 3:08:57 AM

I am reading the RAM FAQ and it has lot of info, and it explains what backwards compatability means as well as my question on reaching half the speed, ie 166 not 333 with DDR333. However this leave my final two main questions:
1) How do I use "dual channel memory" and how do I know if my mobo has this?
2) Is it possible to OC a 1.8 (100*18) to 3.0 (166*18) which would seem the ideal FSB for DDR333?<P ID="edit"><FONT SIZE=-1><EM>Edited by badger86 on 06/09/03 08:26 PM.</EM></FONT></P>
June 10, 2003 4:03:38 AM

With the MB and DDR, as far as I know- well with my motherboard it goes like this. It's automatic enable as soon as you put a memory module in the last memory bank, (so obivously you need another module in the first or second bank- but I don't see why second unless there is a problem so I would go first.) Read up on your MB book and should explain it. But as far as I know- it automatic.

I'm not too sure on the OC isssue- but I don't think you can without burning up your CPU and possibly more. I don't have much information on OC'ing but depends on what kind of CPU you are using, motherboard/ bios (what stepping it has and what it can handle), and cooling. For the overclocking- you might want to hit an overclocking website that really explains it all so you don't burn something out!!! Just my two cents.

<font color=blue>/Next time there is a war in Europe- the loser gets stuck with France this time.</font color=blue> Support your troops!!!!
June 10, 2003 4:49:47 AM

Okay. So to the best of my knowledge if my computer had special dual memory capabilities it would say so on the Asus website or in the manual... Secondly, DDR333 is probably too fast because I can't reach 166FSB without some crazy cooling system so I probably should have gotten PC2100 DDR266 (FSB133). If I am wrong or are missing something any more info would be great. Otherwise thanks for the input guys, these forums are great.
June 10, 2003 3:02:32 PM

"Okay. So to the best of my knowledge if my computer had special dual memory capabilities it would say so on the Asus website or in the manual..."

Correct. The Chipset would either be one from the nVidia nForce Series or one from the Intel i865 or i875 series. If your chipset is not any one of these then you do not have a dual channel memory capable motherboard.



"Secondly, DDR333 is probably too fast because I can't reach 166FSB without some crazy cooling system so I probably should have gotten PC2100 DDR266 (FSB133)."

You are correct. However you might be able to run your memory at the same speed as the FSB. (depends on your available BIOS memory settings) Some setup can actually run better with the memory bus being faster. "Generally" a 1:1 ratio between the FSB and the Memory Bus yields the best results. The only way to tel in your specific setup is to test it both ways.



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June 10, 2003 8:11:24 PM

Thanks. I really appreciate straightforward answers. In Bios my options are "1:1, 4:3, 4:5" and another i forget. 5:4 is not available which would make them on par so I will leave it at 1:1.
June 10, 2003 11:25:42 PM

That's what I have and I recommend that for right now. In the future if you understand the whole system more and want to take a stab at it, you can try your hand at overclocking more- but even then 1:1 is ideal

<font color=blue>/Next time there is a war in Europe- the loser gets stuck with France this time.</font color=blue> Support your troops!!!!
a b } Memory
June 11, 2003 7:29:12 AM

1) 2 chips of 256MB can run cooler and allow for slightly tighter memory timings (or better overclocking) than 1 512MB stick (this is only true most of the time). Also you need 2 stick if you ever go to a Dual Channel board to enable that feature
2) PC3200 refers to 3200 megabytes per second. This is the transfer rate from the RAM to the chipset's memory controller. Older RDRAM (PC1066) was rated in MHz (533MHz using double data rate). PC133 and similar was rated in true MHz.
3) Run your RAM and your CPU bus at the same speed. Sometimes running "in sync" is a BAD idea for performance, because in your case single channel DDR SDRAM has only half the bandwidth of your Quad Data Rate bus!
4) Yes, but you have to run at the rate of the slowest module
5) You can overclock RAM slightly, or underclock as much as needed. I've ran PC133 at PC66 speed and never had problems (over several hundred systems).
6) Some RAM is overrated, slightly defective, etc. There is also ratings for Cas Latency, fewer cycles of latency result in better performance.
7) For your board, PC2700 Cas2 or PC3200 Cas2 (you can probably run PC3200 Cas2.5 at Cas2 if you underclock it to PC2700 speed).
8) Your RAM is Double Data Rate. Your CPU is Quad Data Rate. Both have the same buswidth, so running both at the same speed results in your RAM having half the bandwidth desired by the CPU. Ideally you would want your single channel RAM to run at 2x the bus speed of the processor, but that would limit you to using PC3200 with a stock CPU speed!
9) Run your CPU at 133MHz bus (QDR533) to get it to 2.4GHz. Use the 4:5 CPU:RAM bus speed ratio to get 133MHz CPU bus and 166MHz RAM bus. Use 1.60v core for stability. You can raise that to 1.65v and try overclocking farther, but you will find a limit where the system will become unstable (probably around 2600-2700MHz).

<font color=blue>Watts mean squat if you don't have quality!</font color=blue>
June 11, 2003 8:08:12 AM

I really appreciate you spending the time to go through all 9 questions, but you use some terminology I have not encountered. What is:
-Quad Data Rate
-Cas2 or Cas2.5
and what does "in your case single channel DDR SDRAM has only half the bandwidth of your Quad Data Rate bus" mean? I will go ahead and use the 4:5 ratio however I feel I should also know exactly what you meant :)  Thanks again for the help!
a b } Memory
June 11, 2003 9:21:12 AM

Quad means 4. You know what Double Data Rate is, Quad Data Rate is "doubled DDR". Double data rate (DDR) transfers data 2 times per clock cycle, Quad Data Rate (QDR) does it 4 times per clock cycle.

I believe the Cas Latency info is in the FAQ. It refers to the number of cycles it takes your memory to respond. Fewer cycles of latency mean quicker responses.



<font color=blue>Watts mean squat if you don't have quality!</font color=blue>
June 11, 2003 7:19:33 PM

Sorry my questions about QDR was more about where does it come from? Is it a motherboard feature or RAM, because I have only heard of DDR RAM but nothing to do with QDR before.
a b } Memory
June 12, 2003 2:13:31 AM

I think I already told you, Intel uses QDR tech on the CPU bus. This is the bus from the processor to the northbridge (including memory controller).

Think of QDR like you would AGP4x, and DDR as you would AGP2x. Now think beyond the AGP bus to the processor bus. They use "4x" technology to transfer data from the CPU to the memory controller.

You can plainly understand that if the bus from the CPU to the memory controller is 4x (ie QDR), but the bus from the memory controller to the RAM is 2x (ie DDR), you have half as much speed on the memory side!

This is why Dual Channel DDR was developed for Intel processors, instead of speeding up the bus, they made it twice as wide.

Since both single channel SDRAM (including DDR SDRAM) and the CPU have a 64-bit wide path (ie, 64 data wires, which are called "traces"), increasing the RAM bus to 128 bits (ie, doubling the number of traces) allows it to transfer twice as much data.

If you run a "400" bus P4 (100MHz using QDR) with a "200" bus DDR SDRAM (100MHz using DDR), they are synchonous because of the same 100MHz clock rate, but not optimized because QDR is 4x while DDR is 2x. Adding a second memory channel (ie, Dual Channel) gives you the additional 2x needed to make up the difference.

But since your board doesn't SUPPORT Dual Channel memory operation, you can't DO that. Therefore in order to run the thing "perfectly" you need to run your single channel DDR SDRAM ASYCHRONOUSLY! If you ran the CPU at 100MHz bus (QDR400) and the RAM at 200MHz bus (DDR400), it would work good.

But your board doesn't SUPPORT running your memory bus at twice the frequency of your CPU bus, and you'd be unable to overclock your bus!

So now you reach a comprimise. You run your memory as fast as you can, and your CPU bus as fast as you can to overclock. And a good comprimise seems to be running your CPU bus at 133MHz (QDR533), and your memory at 166MHz (DDR333). It's not ideal, no, but it does give you 2.4GHz CPU speed, and that CPU:D RAM ratio is about the best you can do with what you have!

<font color=blue>Watts mean squat if you don't have quality!</font color=blue>
June 12, 2003 3:36:38 AM

I'm sure you probably alluded to it but that was a very good explanation thank you. Even I understood what you were talking about, I really appreciate it. Understanding the whole thing will make upgrading and future OC much easier.
!