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Am I getting the right stuff?

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  • New Build
  • RAM
  • CPUs
  • Systems
  • Product
Last response: in Systems
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January 15, 2009 10:51:38 PM

Ok getting a new MoBo, CPU, and RAM.

I need some clarification. Now when I am selecting my CPU and RAM is it true I want the core clock speeds the same? For instance, if I want to get 1066mhz ram does my core to my CPU have to be 1066mhz for the best performance? How do I get the numbers? Divide the speed of the CPU by the cores? Divide DDR2 ram by 2?

Also I am looking at even some of the ram, and became a bit confused. From what I understand I want a low CAS correct? I see some with a 6 or 7 cas that are more expensive then the 5's.

Thanks!

More about : stuff

January 16, 2009 8:24:26 AM

I'm assuming that you're going with the older LGA 775 platform because you mention DDR2. If you're meaning the new i7, it's different because they don't have a front side bus.

CPUs have a multiplier. E.g. on the Q6600 it's 9x and on the E8500 it's 9.5x. This is a multiple of the front side bus (FSB) to get listed speed. E.g. Q6600 is 9x266=2.4GHz and E8500 is 9.5x333=3.16GHz.

What is normally listed as the "front side bus" is quad pumped, so that's why the Q6600 lists FSB as 1066 MHz and for the E8500 it's 1333 MHz.

For DDR2 RAM, take the non-quad pumped FSB and double pump to get RAM speed. E.g. if 333 FSB, then DDR2-667 at stock. Buy RAM that runs at this speed or higher. If you want to OC, then you can either get RAM that is spec'd at a high speed, in which case you will OC within the spec, or you can get slower RAM and OC that, but there's a risk it won't go beyond a certain point.

If you want to get fancy, then you can also run a memory divider to increase the RAM speed even further.

Here is an overall example for the E8500 when overclocked:
FSB 450
9.5x450=4.275GHz CPU speed
DDR2-900 at stock
Run memory divider of 6/5 to get (6/5)x900=1080 for DDR2-1080 (either OC DDR2-1066 or buy DDR2-1100 and it's guaranteed)

Get the lowest possible latency and timings, but when you OC low latency memory, you'll have to relax the timings out a bit. There is a relationship between higher speed and higher latency that corresponds to lower speed and lower latency, see if you can find it.
January 16, 2009 12:36:31 PM

I am scared to OC, I am not going to lie. Currently I have a Pentium D 3.4Ghz dual core. I have 800mhz single channel DDR2, the msi website, says it supports 667mhz single channel, tigerdirect.com, and amazon i think say 800mhz. So I think I am getting a new board thats dual channel and supports better memory.

Let me just see if I understand, even though you explained it beautifully.

When I look it up on the processorfinder.intel.com it says my core/bus ratio is 17, my bus speed is 800mhz. That equals 13600mhz. Now thats wrong, but assuming its "quad pumped" and I divide that by 4, I get 3400mhz.

What really blows my mind is, if I take that 200mhz (800mhz non quad pumped correct?) I double it for 400mhz.

Ok, I guess that makes sense... I guess... I don't know. So if the ram is higher, thats ok? it doesn't have to be the same though right? Is it better that it is 800mhz ram with a 400mhz recommended? Since it doubles I mean, is it more "syncronized" then lets say 1066mhz would be?
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January 16, 2009 2:06:12 PM

Pentium D 3.4GHz Dual-Core:
Presler 945 65nm 95w FSB@800MHz
The Northbridge chip (quad pumped) actually runs at 200MHZ.
The cpu thus has a 17 multiplier (200x17=3400 or 3.4GHz).
For single channel memory to be in sync, you need DDR2-800.
For dual channel memory to be in sync, you need DDR2-400.
These values will provide the necessary system bandwidth.

Now, a motherboard will read a small chip (SPD) on the memory dimm to set the default speed.
Often this is not in sync with the cpu/fsb but it still works. As an example, an
E8400 cpu runs x9 on a 333MHz bus,(fsb quad pumped will be called 1333MHZ), for 3GHz.
If you put 2 sticks of DDR2-800 the SPD will tell the motherboard to run it at DDR2-800 or
an actual speed of 400MHz. To put it in sync you actually clock it back down to 333MHZ
or DDR2-667 in dual channel. It doesn't help that often the bios will tell you the speed is 667
when in fact it is 333!

So in fact you have memory of sufficient speed for your processor right now. Your motherboard
may not be running it fast enough though, if 667MHz single channel is the best it can do.
It may well be that with another stick of ram, that running dual channel on your current
board will provide enough memory bandwidth, since in dual channel an actual speed of 200MHz will
be enough. Obviously a new motherboard will do this with ease.
January 16, 2009 3:23:38 PM

I am getting a new MoBo, that supports 1066mhz ram or higher. I want to really put some love towards this thing. I almost got a AMD dual core black edition, like literally two seconds ago, i swung back to this forum. So I should be running my ram at a frequency equal to my fsb?

Answer me this. How bad is my cpu? According to what I am reading it sounds like I am not going to be using anything bigger then 800mhz dual channel. Lets take this processor for example, pretending I am buying it.

http://processorfinder.intel.com/details.aspx?sSpec=SLA...

I am going to be using 800mhz Dual channel ram to maximize performance correct? 1066mhz would not be as good right? I figure bus speed is 1600mhz / 4 = 400mhz multiplier is 8 = 3.2ghz. So I would want dual channel DDR2 800mhz ram right?
January 16, 2009 3:33:09 PM

1600Mhz fsb means an actual northbridge chip speed of 400MHz.
DDR2-800 memory in dual channel mode will meet the system needs.
Memory rated faster (like DDR2-1066) can either be run out of sync at its rated actual 533MHz, or can be clocked back to be in sync at an actual 400MHz.
Faster than needed ram is most often bought to be sync'd back down to 400Mhz, and then the whole system can be overclocked without exceeding the ram's speed limits.
January 16, 2009 3:42:25 PM

Ok so I would still be safe buying faster ram, I should just clock it back. That does make sense. With today's applications, I should probaly upgrade my CPU while I am at it huh? Thanks for the help too. I am getting closer and more confident to the buy button. Its hard for me because I want to do this myself, and just back myself out.
January 17, 2009 7:42:15 AM

Your CPU is not "bad" at all. It's actually a very good chip. However, you're probably at about the point where it feels slow and would therefore like to buy a new computer, right?

With your example of the QX9770, you would use DDR2-800 at stock settings. That is perfectly fine. However, what you didn't realize there is that the QX9770 is in the "Extreme" series of processors, those that can have their multipliers "unlocked". Therefore, its multiplier is not really 8, but can be set higher by the user. You would only buy that QX processor for extreme overclocking purposes.

If you were to ask me what RAM you should get with the QX9770 to maximize performance, I would say get the fastest DDR2 that you can get your hands on. With that particular processor, you can overclock by raising the FSB, the multiplier and also run high RAM dividers to maximize speed. It's up to you to come up with a formula that works--that's overclocking.

Think of it this way. DDR2-1066 has a "speed limit" of 1066. The manufacturer guarantees it to run at 1066, but you can run it at 800 if you'd like. If you buy DDR2-800, then the manufacturer only guarantees a speed up to 800. Beyond that point, you're on your own. Granted, DDR2-800 can be overclocked above 800--this is frequently done. However, you have no idea how fast it can actually run. Manufacturing variance means each chip will have a different top speed--the factory makes a batch of chips and then the manufacturer tests them to see how fast they run. The slow ones get labelled 800 and the fast ones get the 1066 badge.

Don't buy fast RAM if you're not going to use the speed. For example, let's say you bought that QX9770 and wanted to just run it at stock 400FSB at synchronous (1:1) memory mode. Then it is a waste of money to buy anything more than DDR2-800. However, sometimes faster RAM is on sale at a price below the slower ones. For example, I think that OCZ Reaper DDR2-1066 was selling for $40 the other day. That is a very good deal.

One last thing to note about RAM. All RAM running at the same speed will be the same. For example, if you were to use DDR2-800 and run it at 400FSB, then it doesn't matter if you're using Corsair Dominator or cheap no-name brand. It's all going to run at the exact same speed. Just like when driving the Interstate, all cars running at 60 mph are going the same speed, whether they are Porsches or Civics.

The real difference in RAM is that some can run at higher speeds than others, which is really where the value lies in expensive RAM. Just like how a Porsche has a higher top speed than a Civic.

Does that help?
January 18, 2009 1:32:26 AM

yes it actually helps alot. I am glad you talked about unlocking the multiplier. I thought that was any cpu, I was going to get a better mobo with better dual channel ram and overclock the cpu, I didn't realize mine couldn't do that. So that really out of the question. Its not a BAD computer, I just want to get more like you said. So would it still be a better idea to get a better mobo that supports dual channel ram? If so what speed would I need to get to run it at FSB, 400mhz? Does that even exist, and would the dual channel be better then the single channel I am running now?
January 20, 2009 6:33:29 AM

Just a point about overclocking your existing setup. Just because your CPU has a locked multiplier doesn't mean that you can't overclock it. You can try raising your FSB because (FSB)x(multiplier)=CPU speed. The Extreme processors can overclock by raising both variables, not just one. Unless you mean that you cannot overclock because you have a locked BIOS, in which case you're out of luck.

Of course you would buy a modern mobo today that supports dual channel RAM because dual channel has twice the bandwidth of single channel at the same speed.

If you want to run FSB 400, then look for a mobo that either states specifically that it supports FSB 1600 (because of quad pumping), or one that supports FSB 1333 (or less) that is known to overclock up to FSB 1600.

The manufacturer may not specifically say that a mobo supports a particular FSB, but BIOS allows you to set a higher FSB for overclocking. For example, my BIOS/mobo allows me to set an FSB between 200 and 800 MHz.

Then you would buy DDR2-800 RAM, in either 2x1GB or preferably 2x2GB configuration.

Using the example of Intel processors, if you want an easy overclock to 400FSB, then I'd suggest you get something that runs at FSB 1333 stock, like a Q9550 or a E8500, both of which will hit FSB 400 pretty easily.
January 20, 2009 4:53:15 PM

Yes I looked at it last night, got the jeebies and rolled out like a b****. I don't want to blow my stuff up, but it DID allow me to change the FSB but the multiplier was grey so yes your right, and I understand the FSB thing now.

So just to clarify, CPU's are quad pumped, DDR2 is double pumped. So I need to divide the FSB by 4, and the RAM by 2, and for max performance those should have the same core speed. E.g. OC a 1333mhz to 1600mhz, grab some DDR2 dual channel RAM at 800mhz.

I am looking at this product, I have done some researching and it seems like the best price/performance deal to me...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

So if I could unlock the multiplier, correct me if I am wrong, I would lower it to keep the total speed down so it won't fry the CPU?

If I wanted to just grab a mobo and ram and wanted to run DDR2 667mhz ram I would need to clock the CPU FSB to 333mhz correct? This would put the total speed at 333 x 17 = 5.66ghz, which I am sure is impossible for almost any CPU, especially mine.

Do I sound like I am figuring it out, or am I still lacking the understanding?

January 21, 2009 4:17:48 AM

Why don't you have a read of these guides:

How to Overclock Quads & Duos

Temperature Guide

They explain it much better than I could and I think that you need to understand a few more basic relationships between the parts first. It's more than just the speed numbers--understand how voltage and temperature fits into this equation too.

It would also help if you gave us an idea of where you're coming from (current specs), your available budget, usage needs and where you want to go. That knowledge is how people on these forums are able to help you better. Right now, it's a little difficult to advise you in a vacuum.

And don't worry, if you do it right, nothing will blow up.
!