Help me understanding E4300 Overclocking Memory Requirement

[Peter007]

I have been out of the computer world since....DDR1 / 805D / ATI 9500.
I could use your Help in updating my knowlege base regarding DDR2 & Overclocking.
I'm excited to read Anandn's excellent review on: E4300 Overclockable.
But I struggle to understand the DDR2 Timing issue:

We wanted to showcase the performance potential of the E4300 without resorting to more expensive 1066MHz or faster memory and thus we used a 2:1 memory-to-FSB ratio at stock speeds (DDR2-800) and 1:1 ratio for overclocking, resulting in our memory running at DDR2-750. With more expensive memory the overclocked E4300 would perform even better but our focus was on best bang for your buck with the chip and how well it can overclock. As you will soon see, you don't need anything faster than DDR2-800 memory to make the E4300 a very compelling chip.

1. How much cheaper is it to buy DDR2-800, can I get by using even less expensive DDR2 memory?
....For example, in the AthlonXP days, many DDR1-133mhz works equally well @166mhz.

2. Explain "2:1 memory-to-FSB ratio at stock speeds (DDR2-800) and 1:1 ratio for overclocking"
....Does DDR2 (@1:1) mean it can run @800mhz?
....By that token, all I need is a DDR2-400, since the overclockable fsb is only @375mhz, no?
....IF my overclockable goal is @400mhz fsb = 9x400= 3600mhz, what is the minimum DDR2 memory I need to buy?

Thanks for any answers you can provide. IF you can provide a link to a good price DDR2 memory @reasonable price, I appreciate that too.

Sincerely,

from a very ancient anandtech member

 

[harpoon84]

1) Yes, you can buy cheaper than DDR2-800 memory. Most DDR2-667 will overclock to DDR2-800 speeds.

2) The E4300 has a quad pumped 200MHz stock FSB (Netburst style), for an 'effective' FSB of 800MHz. The E4300 @ 3.37GHz runs at a 375MHz FSB QP, or 1500MHz FSB effective. 2:1 RAM:FSB ratio means you need DDR2-750. Most DDR2-667 should overlclock to such speeds.

 

[Roguestar]

The DDR2 generally runs at twice the speed of the FSB. So if someone says a 1:1 ratio they usually mean if you have a FSB of 400Mhz you will need RAM of 800Mhz.

Long story short, if you want a 400Mhz FSB you need DDR2-800 rated RAM, or lower that will overclock well.

Here's a core 2 duo memory guide thread, mostly aimed towards overclocking:
http://forums.anandtech.com/messageview...atid=28&threadid=1966035&enterthread=y

 

[Assimilator1]

I'm trying to get to grips with DDR2 & Conroe FSB/RAM needs too.

So if someone says a 1:1 ratio they usually mean if you have a FSB of 400Mhz you will need RAM of 800Mhz.

Is this because DDR2 800 actually runs at 400MHz and the 800'MHz' your quoting is the effective speed?

Another thing is those stupid bandwidth numbers they like to rate RAM at (why can't they stick to effective MHz speed?:frown: ) ,my regular shop is selling the following DDR2 RAM :-

PC 4200 = DDR2 533 MHz = 266.5 MHz ,real clock
PC 5400 = DDR2 667 MHz = 333.5 MHz
PC 6400 = DDR2 800 MHz = 400 MHz
PC 7200 = DDR2 900 MHz = 450 MHz
PC 8000 = DDR2 1000 MHz = 500 MHz
PC 8500 = DDR2 1066 MHz = 533 MHz

Is that right?

Btw wouldn't DDR2 533 be slower than old DDR400 due to higher latencies? (not that you can use DDR 400 on most S775 mbrds though)

What RAM/FSB dividers are typically available on S775 mbrds?

So with an E4300 running 200MHz QP FSB (=800FSB) with a 2:1 RAM/FSB ratio the RAM is running at 400MHz (twice the FSB),which is DDR2 800 ,have I got that right?

What sort of performance hit does the Conroe take if running slower RAM? say DDR2 533.
Any benchmarks on that?

 

[nyker96]

you can buy lower than 800 rams but you might be risking a non 1:1 ratio after OC. no biggie just a little less performance from your ram.

 

[Roguestar]

Mos P965 and 975X boards also cannot run the memory at a lower ratio than 1:1 with the FSB (ie: memory divider) so with those chipsets you need RAM rated at least twice the speed you want the FSB to be.

 

[Avalon]

Originally posted by: Assimilator1
I'm trying to get to grips with DDR2 & Conroe FSB/RAM needs too.

So if someone says a 1:1 ratio they usually mean if you have a FSB of 400Mhz you will need RAM of 800Mhz.

Is this because DDR2 800 actually runs at 400MHz and the 800'MHz' your quoting is the effective speed?

Yeah, that's how it works.

Another thing is those stupid bandwidth numbers they like to rate RAM at (why can't they stick to effective MHz speed?:frown: ) ,my regular shop is selling the following DDR2 RAM :-

PC 4200 = DDR2 533 MHz = 266.5 MHz ,real clock
PC 5400 = DDR2 667 MHz = 333.5 MHz
PC 6400 = DDR2 800 MHz = 400 MHz
PC 7200 = DDR2 900 MHz = 450 MHz
PC 8000 = DDR2 1000 MHz = 500 MHz
PC 8500 = DDR2 1066 MHz = 533 MHz

Is that right?

Right. Which is why when in the AT review they said they used a 2:1 memory to FSB ratio at stock speeds (DDR2-800) the memory would have effectively been running at 200Mhz (400 effective) if left at 1:1 because the E4300's stock FSB speed is 200Mhz(800 effective).

Btw wouldn't DDR2 533 be slower than old DDR400 due to higher latencies? (not that you can use DDR 400 on most S775 mbrds though)

For the most part, yes, unless an application you were benching in heavily favored bandwidth.

What RAM/FSB dividers are typically available on S775 mbrds?

Usually no dividers for Intel chipset boards, but more of multipliers to increase the memory speed beyond the FSB. Although, ATI and Nvidia chipset based boards coming out are allowing unlinked memory/FSB and have options for your basic memory dividers.

So with an E4300 running 200MHz QP FSB (=800FSB) with a 2:1 RAM/FSB ratio the RAM is running at 400MHz (twice the FSB),which is DDR2 800 ,have I got that right?

What sort of performance hit does the Conroe take if running slower RAM? say DDR2 533.
Any benchmarks on that?

Right. And for the performance hit, it's very little if we're comparing to good DDR2-800. We're talking several percentage points in the majority of applications. But, your cheapest memory these days isn't much less than DDR2-800 now. It's starting to become very mainstream, which is a good thing. No reason to be buying DDR2-533 any more.

 

[DrMrLordX]

Actually, DDR2-800 runs at 200 mhz, not 400 mhz. We just tend to think of it running at 400 mhz in order to sort out how fast it will run when we use a 1:1 memory ratio with a FSB or HTT of 400 mhz.

 

[harpoon84]

Originally posted by: DrMrLordX
Actually, DDR2-800 runs at 200 mhz, not 400 mhz. We just tend to think of it running at 400 mhz in order to sort out how fast it will run when we use a 1:1 memory ratio with a FSB or HTT of 400 mhz.

What? DDR2-800 runs at 400MHz.

DDR stands for 'Double Data Rate' so at 400MHz it is effectively running at 800MHz since the data is 'double pumped' per cycle.

 

[EarthwormJim]

Originally posted by: harpoon84

Originally posted by: DrMrLordX
Actually, DDR2-800 runs at 200 mhz, not 400 mhz. We just tend to think of it running at 400 mhz in order to sort out how fast it will run when we use a 1:1 memory ratio with a FSB or HTT of 400 mhz.

What? DDR2-800 runs at 400MHz.

DDR stands for 'Double Data Rate' so at 400MHz it is effectively running at 800MHz since the data is 'double pumped' per cycle.

I thought DDR2 was quad pumped, hence the 2 (2 times ddr).

 

[harpoon84]

Originally posted by: EarthwormJim

Originally posted by: harpoon84

Originally posted by: DrMrLordX
Actually, DDR2-800 runs at 200 mhz, not 400 mhz. We just tend to think of it running at 400 mhz in order to sort out how fast it will run when we use a 1:1 memory ratio with a FSB or HTT of 400 mhz.

What? DDR2-800 runs at 400MHz.

DDR stands for 'Double Data Rate' so at 400MHz it is effectively running at 800MHz since the data is 'double pumped' per cycle.

I thought DDR2 was quad pumped, hence the 2 (2 times ddr).

You thought wrong.

http://en.wikipedia.org/wiki/DDR2_SDRAM

 

[DrMrLordX]

Originally posted by: harpoon84

DDR stands for 'Double Data Rate' so at 400MHz it is effectively running at 800MHz since the data is 'double pumped' per cycle.

From the article on Wikipedia you linked:

Like all SDRAM implementations, DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called double pumping). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, allowing transfers from two different cells to occur in the same memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

Therefore, DDR2 can transfer at the rise and fall of the clock, AND it can transfer from two different cells per clock . . . effectively allowing 4 transfers per clock.

Look at the chart in the article under Specification Standards. You'll see that DDR2-800 runs at 200 mhz with a 400 mhz memory bus.

 

[Assimilator1]

Right I get it now ,but the important part for RAM/FSB ratio calculations is that the bus between RAM & chipset is running at 400MHz for DDR2 800.

Avalon
Thanks for that ,I noticed with the RAM prices that there wasn't much difference between DDR2 533 & 667 ,but 667 was still quite a bit cheaper than 800.
£90 for 1GB of OCZ DDR2 800 vs ~£76 for 1GB of DDR2 667 OCZ/Kingston or Crucial (excluding rubbishy non branded stuff).But DDR2 800 is not too much more expensive

 

[harpoon84]

Originally posted by: DrMrLordX

Originally posted by: harpoon84

DDR stands for 'Double Data Rate' so at 400MHz it is effectively running at 800MHz since the data is 'double pumped' per cycle.

From the article on Wikipedia you linked:

Like all SDRAM implementations, DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called double pumping). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, allowing transfers from two different cells to occur in the same memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

Therefore, DDR2 can transfer at the rise and fall of the clock, AND it can transfer from two different cells per clock . . . effectively allowing 4 transfers per clock.

Look at the chart in the article under Specification Standards. You'll see that DDR2-800 runs at 200 mhz with a 400 mhz memory bus.

Sorry, I got the 'bus clock' and 'memory clock' mixed up. I stand corrected. Thanks.

 

[Yongsta]

I have two sticks of 1GB DDR2-667. So with the 9x multiplier I should be able to get the E4300 to 3.0 ghz (9x333) with this ram leaving it at 1:1. Hopefully I can go a little higher but I'm excited about this new chip. Anyone can recommend an affordable motherboard for the E4300 that should have no problem overclocking it to the 3 - 3.4 ghz range?

 

[Peter007]

Thanks for all who reply so far. I don't fully understand it yet, but I'm beginning to get it. DDR2 operates @twice the stated speed, so DDR2-800 memory only runs @400mhz, thus enabling the Anandtech's E4300 review to overclock to 375fsb. However, I"m still confuse about the 2:1 vs 1:1. [1] IS 1:1 alway smore preferrable to 2:1 memory timing? Why on earth would anyone want to leave it @2:1? Am I also correct to assume that I get significatn boot in performance switching to 1:1 memory timing even if I don't overclock?

 

[Avalon]

Originally posted by: Peter007
Thanks for all who reply so far. I don't fully understand it yet, but I'm beginning to get it. DDR2 operates @twice the stated speed, so DDR2-800 memory only runs @400mhz, thus enabling the Anandtech's E4300 review to overclock to 375fsb. However, I"m still confuse about the 2:1 vs 1:1. [1] IS 1:1 alway smore preferrable to 2:1 memory timing? Why on earth would anyone want to leave it @2:1? Am I also correct to assume that I get significatn boot in performance switching to 1:1 memory timing even if I don't overclock?

2:1 just allows you to run your memory twice as fast as your system bus, so if it can handle it, you'll get a huge boost in memory bandwidth. Once you start overclocking moderately, you'll likely not be able to run at that memory multiplier.

 

[DrMrLordX]

Originally posted by: harpoon84

Sorry, I got the 'bus clock' and 'memory clock' mixed up. I stand corrected. Thanks.

No problem. DDR2 is pretty weird in that the chips run at a different speed than their own dedicated memory bus. I can only imagine what DDR3 is going to be like . . .

http://en.wikipedia.org/wiki/DDR3

DDR3-800 chips will only run at 100 mhz? Crazy. I can't wait to see the timings on these things, ugh. 7-7-7-20 anyone? *P

 

[The Sauce]

Ok, ok ... let me see if I have this straight:

If the FSB is running @ 200 MHz, then the DDR2 runs @ 400 MHz (i.e. DDR2-800)

So, to run a 200 MHz FSB you need a minimum of DDR2-800 (which runs @ 400 MHz).
Do I have that right?

If so then how could you overclock the FSB to 375 (like Anand did) with only DDR2-800?
If I was right and the FSB is running at 375, then the DDR is running at 750 and you would need DDR2-1500.

That's what I don't quite understand.

 

[harpoon84]

Originally posted by: Snatchface
Ok, ok ... let me see if I have this straight:

If the FSB is running @ 200 MHz, then the DDR2 runs @ 400 MHz (i.e. DDR2-800)

So, to run a 200 MHz FSB you need a minimum of DDR2-800 (which runs @ 400 MHz).
Do I have that right?

If so then how could you overclock the FSB to 375 (like Anand did) with only DDR2-800?
If I was right and the FSB is running at 375, then the DDR is running at 750 and you would need DDR2-1500.

That's what I don't quite understand.

LOL it's pretty hard to explain actually once you're confused.

When they say '200MHz FSB' they mean before it's quad pumped, it's really effectively an '800MHz FSB'.

200MHz/800MHz is the *stock* FSB speed of the E4300. With a 2:1 FSB to RAM ratio, you need a minimum of DDR2-400 to run an E4300 at stock 800MHz FSB.

An E4300 at, let's say a nice rounded 3GHz, would run at a FSB of 333MHz/1333MHz. Thus, with the 2:1 divider, you need DDR2-667.

So basically, you divide the FSB (*after* quad pumping) by half, or multiply the FSB (*before* quad pumping) by 2x to get the required RAM speed.

 

[myocardia]

Originally posted by: harpoon84
LOL it's pretty hard to explain actually once you're confused.

When they say '200MHz FSB' they mean before it's quad pumped, it's really effectively an '800MHz FSB'.

200MHz/800MHz is the *stock* FSB speed of the E4300. With a 2:1 FSB to RAM ratio, you need a minimum of DDR2-400 to run an E4300 at stock 800MHz FSB.

An E4300 at, let's say a nice rounded 3GHz, would run at a FSB of 333MHz/1333MHz. Thus, with the 2:1 divider, you need DDR2-667.

So basically, you divide the FSB (*after* quad pumping) by half, or multiply the FSB (*before* quad pumping) by 2x to get the required RAM speed.

What he's trying to say is that assuming you aren't going to overclock, you only have to buy PC2 3200 RAM. Not that you should be buying PC2 3200. And anything faster, like PC4200 (533 DDR) or PC5300 (667 DDR) will allow you to overclock. That's the reason that this processor is selling for more $$ than the E6300-- people are excited about it, because it allows fairly high overclocks, with cheaper RAM.

 

[gerwen]

Another attempt to explain clearly:

Ignore all the discussion of double rates, quad pumped and all that. It's more than you need to know to get a system working.

What do you need to know?

Your ram must be rated at double the Front Side Bus you intend to use.

example: if you want a 4300 to run at 3.0 GHz(9x333), you will run a 333 FSB, so you need DDR2-667 memory. (Or memory that will overclock to DDR2-667.

If you want to overclock an E6400 to 3.2 GHz(8x400) you will run a 400 FSB. You will need DDR2-800 Memory.

 

[Assimilator1]

Originally posted by: gerwen
Another attempt to explain clearly:

Ignore all the discussion of double rates, quad pumped and all that. It's more than you need to know to get a system working.

What do you need to know?

Your ram must be rated at double the Front Side Bus you intend to use.[edit]when overclocking & running a 1:1 RAM:FSB ratio

example: if you want a 4300 to run at 3.0 GHz(9x333), you will run a 333 FSB, so you need DDR2-667 memory. (Or memory that will overclock to DDR2-667.

If you want to overclock an E6400 to 3.2 GHz(8x400) you will run a 400 FSB. You will need DDR2-800 Memory.

Yes but your missing the point that at default FSB (200) you run DDR2 800 (400MHz) RAM bus at double the FSB speed to get the right RAM speed.

Originally posted by: Snatchface
Ok, ok ... let me see if I have this straight:

If the FSB is running @ 200 MHz, then the DDR2 runs @ 400 MHz (i.e. DDR2-800)

So, to run a 200 MHz FSB you need a minimum of DDR2-800 (which runs @ 400 MHz).
Do I have that right? - No ,you could run your RAM at 1:1 on std FSB giving 200MHz RAM bus clock ,but of course it won't do performance much good

If so then how could you overclock the FSB to 375 (like Anand did) with only DDR2-800?
If I was right and the FSB is running at 375, then the DDR is running at 750 and you would need DDR2-1500. - he drops the the RAM:FSB ratio from 2:1 to 1:1 ,halving RAM bus speed

That's what I don't quite understand.

Added answers

I get it now ,but what I would like to know is other than 1:1 & 2:1 what other RAM multipliers are available?
Presumabley their are multipliers to allow DDR2 533 & 667 to run at full speed on the def 200FSB?

 

[gerwen]

Originally posted by: Assimilator1

Originally posted by: gerwen
Another attempt to explain clearly:

Ignore all the discussion of double rates, quad pumped and all that. It's more than you need to know to get a system working.

What do you need to know?

Your ram must be rated at double the Front Side Bus you intend to use.[edit]when overclocking & running a 1:1 RAM:FSB ratio

example: if you want a 4300 to run at 3.0 GHz(9x333), you will run a 333 FSB, so you need DDR2-667 memory. (Or memory that will overclock to DDR2-667.

If you want to overclock an E6400 to 3.2 GHz(8x400) you will run a 400 FSB. You will need DDR2-800 Memory.

Yes but your missing the point that at default FSB (200) you run DDR2 800 (400MHz) RAM bus at double the FSB speed to get the right RAM speed.

[

I wasn't missing the point. I was trying to clarify what spec your RAM needs to be to get a system to work for any given setup. If you are running stock, you could use any DDR2 ram. Yes, you can run a 200FSB with a ratio of 2:1 to gain some performance if you have ddr2-800. You'll gain a lot more performance by running a 400FSB with a 1:1 ratio though.

 

[Sapiens]

I apologize for intruding on the thread, but Peter007 seems to be in the same boat as I am when it comes to understanding memory speeds with regards to on C2D systems. Let me throw an example out there and someone can correct my terrible math. Going off of the following quote...

Originally posted by: harpoon84
So basically, you divide the FSB (*after* quad pumping) by half, or multiply the FSB (*before* quad pumping) by 2x to get the required RAM speed.

Stock E6600
266 MHz FSB, 9x multiplier = 2.4 GHz
You would need 533 MHz RAM (266*2)

Overclocked E6600
400 MHz FSB with an 8x multiplier = 3.2 GHz
You would need 800 MHz RAM (400*2)

- Would both of these would retain the desirable 1:1 ratio, or am I mucking something up?
- Would this overclock be entirely feasible on something like a P5B Deluxe?
- If you had PC8500 RAM, would running it at PC6400 to attain the 1:1 ratio allow you to set better timings, or would it be better to pick up some high quality PC6400 RAM instead?