Cpu/ram fsb ratios (yeah...)

[asinausk]

First, hello tom's hardware members! I hope this will be the beginning of a long and beautiful relationship...or maybe not, this questions seems to be the bane of geeks everywhere.

ok, i've been reading a lot about fsb ratios but can't seem to get a straight answer, many people use different math...so someone is wrong...i just dont want that to be me. I would like an answer to these questions:

1: are all intel cpu's 'quad-pumped', namely this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16819115059

2: assuming that cpu is quad pumped, my understanding is that i would need ddr2 533 to gain a 1:1 ratio (533 ram / 2 = 266 : 1066 cpu / 4 = 266 = 1:1)

I've also seen people say that I would need 1066 memory, but isn't that actually 533?

I'm thinking about upgrading my cpu to the one above when money allows, i currently have a celeron d 356 3.33ghz (yeah...)

i just got these: http://www.newegg.com/Product/Product.aspx?Item=N82E16820231018

basically, it was all i could afford and all my current mobo could handle.

some people think this is a waste of time, but in my mind synchronous > asynchronous, for many reasons...

hope you guys could shed some light on this seemingly often misunderstood concept

thanks a bunch

 

[Upendra09]

alright you are so confused

first of all CPU and RAm ratios are this

you want your FSb and RAM to be the same 1:1

the dual core has a FSb of 1066 mhz so get RAM that is also 1066 mhz

when RAM is DDR2 it is double data rate which means a 1066 rated DDR2 ram is actually 533 times 2 the one you listed is 266 times 2 tons slower

what the speed is what the speed is you don't multiply by two after it says 533 it won't go any faster unless you OC that

the ideal Ratio is 1:1 so get 800 mhz RAM or 1066 whichever the CPU has or just get 800 mhz RAM and OC it to match the bus speed and then you ahve a ratio of 1:1

 

[jsc]

1. Yes.
2. Yes.

The problem with your memory is that it may give you enough OC headroom to allow for an increase in the FSB frequency. On the other hand, your prospective new CPU has a pretty high internal multiplier, so it won't take much of an increase in FSB speed to yield a significant overclock.

Some of us discuss the 1:1 FSB:RAM ratio here:
http://www.tomshardware.com/forum/251715-29-ratio-myth

 

[jsc]

you want your FSb and RAM to be the same 1:1

Yes.

the dual core has a FSb of 1066 mhz so get RAM that is also 1066 mhz

No.

Definition time (attention purists, I'm talking about DDR2 and I'm simplifying a little ):
Core2 CPU's use a frontside bus (FSB). The FSB is a thing with two main characteristics: speed which is usually defined in MHz and width which in the Core2's is 64 bits wide. We are concerned with the speed.

Using the Q6600 as an example, the FSB frequency is 266 MHz. The matching DDR2 memory clock for that frequency is 533 MHz (266 X 2). DDR2 memory transfers two chunks of data for each bus cycle, hence double the frequency. So, to run 1:1 at an FSB of 266 MHz, we need DDR2-533 RAM. What CPUZ does is a little confusing. It will tell you that the memory frequency is 266 MHz for a 1:1 ratio. It reads the memory clock, I think, and internally divides it by 2 (DDR2 remember?) to arrive at the memory frequency.

The FSB clock is 1066 MHz (266 X 4). The bus is "quad pumped". It transfers 4 chunks of data into and out of the CPU each cycle. So each FSB cycle generates 4 FSB clocks.

I always run my memory at 1:1. That is the FSB freq to mem freq ratio is one to one (that's how CPUZ calculates it. That means that the memclock is twice the FSB freq. It's a little confusing. Running memory slower costs performance. Running memory faster does not give you much if any real world performance increase and it can lead to higher instability.

And while I am talking about memory, let me say, "There ain't no such thing as DDR2-1066 RAM." Got your attention now, yes? DDR2-1066 RAM is simply DDR2-800 RAM that has been tested to run at the higher speed, usually at an increased voltage and more relaxed timings.

 

[asinausk]

1. Yes.
2. Yes.

The problem with your memory is that it may give you enough OC headroom to allow for an increase in the FSB frequency. On the other hand, your prospective new CPU has a pretty high internal multiplier, so it won't take much of an increase in FSB speed to yield a significant overclock.

Some of us discuss the 1:1 FSB:RAM ratio here:
http://www.tomshardware.com/forum/251715-29-ratio-myth

thanks for the quick response jsc, but i'm running into the same problem again. you say im correct in saying that I would need ddr2 533 with a 1066 fsb cpu to achive a 1:1 ratio. the dude above me says I need 1066...

also, I've already read through the thread you recommended, thanks though


EDIT: you've addressed this, thanks lots...

 

[Bluescreendeath]

ouch, the OP got hit by terrible RAM prices >_<

and wow, E7600s cost $144 on Newegg? That's almost as expensive as an E8400 with 3x more cache...

Is Newegg going by the wayside...?

 

[jsc]

My first post was answering yours.
Upendra09 posted the same time I did - look at the time stamps.

My second post was replying to upendra.

 

[FunSurfer]

thanks for the quick response jsc, but i'm running into the same problem again. you say im correct in saying that I would need ddr2 533 with a 1066 fsb cpu to achive a 1:1 ratio. the dude above me says I need 1066...

also, I've already read through the thread you recommended, thanks though


EDIT: you've addressed this, thanks lots...

If you will get a DDR2 533 it will run at 2x266 speed for 1:1 ratio.
If you will get a DDR2 1066 it will underclock and run at 2x266 speed for 1:1 ratio.

For example, I hava a DDR2 800 RAM and 1333 bus CPU.
My Ratio is 1:1 and my RAM is running ay 667 (2x333)

 

[asinausk]

If you will get a DDR2 533 it will run at 2x266 speed for 1:1 ratio.
If you will get a DDR2 1066 it will underclock and run at 2x266 speed for 1:1 ratio.

For example, I hava a DDR2 800 RAM and 1333 bus CPU.
My Ratio is 1:1 and my RAM is running ay 667 (2x333)

what are the benefits of suing ddr2 1066 and underclocking it? will it provide a noticeable performance gain? I've heard that underclocking can have some weird effects, especially with ram.

also, if i get a mobo with say a memory standard off 1066/800/677 could i throw some sticks in of 533 without issues, or should that be avoided?

 

[asinausk]

ouch, the OP got hit by terrible RAM prices >_<

and wow, E7600s cost $144 on Newegg? That's almost as expensive as an E8400 with 3x more cache...

Is Newegg going by the wayside...?

aside from newegg, what are some other good sellers? I've checked out tigerdirect, but i wasn't impressed....at all.

 

[FunSurfer]

what are the benefits of suing ddr2 1066 and underclocking it? will it provide a noticeable performance gain? I've heard that underclocking can have some weird effects, especially with ram.

also, if i get a mobo with say a memory standard off 1066/800/677 could i throw some sticks in of 533 without issues, or should that be avoided?

There is no benefit in underclocking a DDR2 1066 RAM to 533. It will happen if you will force 1:1 FSB-RAM ratio.
If your goal is 1:1 ratio and your CPU FSB is 1066 you should buy DDR2 533 RAM.
If you intend to overclock your CPU in the future, than you should buy faster RAM.
Overclocking the CPU will increase the speed of the FSB also.

I can explain on my PC:
My CPU frequency is 3GHz and my FSB is 1333 (333x4), my RAM is DDR2 800 but it is operating at 667 (333x2)
because I wanted 1:1 FSB-RAM ratio.
If I will overclock my CPU to 3.6GHz, the FSB speed will increase to 1600 (400x4) and my DDR2 800 RAM will
operate at 800 (400x2) to obtain the 1:1 ratio.

You should check the compatibility of the RAM that you buy for all the frequencies that you will use.

A CPU with 1066 FSB and DDR2 533 RAM does not suppose to work on a MoBo with a memory standard of 1066/800/677.
To run a stable PC, it is recommended to buy compatible components ( CPU with 1066 FSB and DDR2 533 RAM for
800/677/533 MoBo or CPU with 1333 FSB and DDR2 677 RAM for 1066/800/677 MoBo).

 

[asinausk]

There is no benefit in underclocking a DDR2 1066 RAM to 533. It will happen if you will force 1:1 FSB-RAM ratio.
If your goal is 1:1 ratio and your CPU FSB is 1066 you should buy DDR2 533 RAM.
If you intend to overclock your CPU in the future, than you should buy faster RAM.
Overclocking the CPU will increase the speed of the FSB also.

I can explain on my PC:
My CPU frequency is 3GHz and my FSB is 1333 (333x4), my RAM is DDR2 800 but it is operating at 667 (333x2)
because I wanted 1:1 FSB-RAM ratio.
If I will overclock my CPU to 3.6GHz, the FSB speed will increase to 1600 (400x4) and my DDR2 800 RAM will
operate at 800 (400x2) to obtain the 1:1 ratio.

You should check the compatibility of the RAM that you buy for all the frequencies that you will use.

A CPU with 1066 FSB and DDR2 533 RAM does not suppose to work on a MoBo with a memory standard of 1066/800/677.
To run a stable PC, it is recommended to buy compatible components ( CPU with 1066 FSB and DDR2 533 RAM for
800/677/533 MoBo or CPU with 1333 FSB and DDR2 677 RAM for 1066/800/677 MoBo).

awesome, thank you

 

[Upendra09]

@jsc

your saying that if a core 2 quad with an fsb of 1066 and a DDR2 RAM at 1066 will not run at a ratio of 1:1?

to the op sorry if i confused you more i thought i had this figured out

 

[asinausk]

@jsc

your saying that if a core 2 quad with an fsb of 1066 and a DDR2 RAM at 1066 will not run at a ratio of 1:1?

to the op sorry if i confused you more i thought i had this figured out

its all good, i've got it figured out now

 

[Keve]

Veterans, im still relatively new to the workings of FSB and i have one question to confirm my understanding:

A 2.9GHZ cpu and mobo that both run on 1066mhz will work fine with 533mhz ddr2 stick since its quadpumped.
The mobos fsb is 266*4=1066
The rams fsb is 266*2=533

Im looking at a:
Intel Core 2 Duo E7500 2.93GHz
Intel D102GGC2
two 2gb sticks of ddr2 522mhz ram

have i got it straight? or is it back to school for me?