One thing also to consider is just not CPU but matching up the CPU with the ram to get best performance. To avoid bottlenecks and allowing everything to communicate at the same speed and not having One Item sitting 1-2 clock cycles waiting for the other to catch up.
Click here and take a look at the 2 red lines on the chart (P4 540 3.2G vs a Core 2 duo 2.13)
You will find P4 pretty low
even a core duo (not a core 2 duo) would still be better
Anyways here is the rest of the Info I told you I would provide.
DDR2 Is not faster it actually has higher latency times then DDR, but for faster CPU's with (using term FSB lightly here) Larger FSB of 1600,2000 ext.. DDR2 in dual mode allows the ram to run closer to that speed
Works something like this. (make note DDR will not fit in DDR2 slots or vise verse)
PC3200 (400Mhz) X2 = 800Mhz (184 Pin)
PC3500 (433Mhz) X2 = 866Mhz (184 Pin)
PC2-8000 (DDR2-1000) x2 = 2000Mhz (240 Pin)
PC2-8500 (DDR2-1066) x2 = 2132Mhz (240 Pin)
Now what does that mean?
Intel 4 Processor Prescott 3EGHz, 800MHz FSB
You see DDR PC3200 works great cause it has 800Mhz
Now
AMD Athlon 64 X2 5200+ Dual Core 2.6GHz, 2x1MB, 2000MHz FSB
PC2-8000 (DDR2-1000) x2 = 2000Mhz works cause it has 2000Mhz
By matching allows you to get the maximum performance, If not the you will have one waiting on the other slowing the system.
But like I said the In order to get the higher clock speeds they had to increase the latency on DDR2. over time I'm sure they will perfect that in time.
2. the CAS speed of ram
CAS Latency: What Is It, and How Does It Impact Performance?
That will explain CAS in its entirety.
That is why the prices are different
Does it really effect speed? sure does, depends allot on the motherboard and size of CPU as well but as far as having a high end gaming system that can run graphics very well then yes this is where you will get the best performance...
significant complaint about DDR2 when it came out--much higher latencies. On the other hand, DDR2 is capable of much much higher speeds--if you shell out you can pick up DDR2 RAM up to DDR2-1111mhz! As a comparison the fastest DDR1 RAM I've seen is 600mhz. Twice the latency, but twice the speed.
As usual, to go faster, often you must either sacrifice latency or use very high voltages.
If you are confused about the mathematics of the whole thing, explains the math well:
CPU speed = CPU multiplier x Front Side Bus
Example:
Core 2 Duo E6600 2.4ghz = 9 * 267mhz
However, even this simple equation has become complicated. For starters, Intel likes to “quad” pump their FSB so they will report it as 267*4=1066mhz, front side bus. I think its best to reduce the math to the lowest denominator and call the front side bus 267mhz. Intel also makes cpus with front side buses of 200mhz and 133mhz (or 800mhz/533mhz quad pumped).
To further complicate things, the latest processors from AMD have a completely different architecture, specifically, the memory controller is built right onto the CPU die. So technically, there is no front side bus, if by front side bus you mean the speed at which the core communicates with the memory controller. AMD chips do have a number which they retain in order to maintain the equation.
Perhaps in response to this confusion, Abit has gone with calling the “Front Side Bus” the “External Clock”. Since we are talking about an Intel platform, I will from here on out use the words FSB and External Clock interchangeably because they both indicate the speed at which the core communicates with the memory controller. In this situation the memory controller and the northbridge are also one in the same, and so I will use them interchangeably as well.
The CPU multiplier is a property intrinsically set by Intel, as far as I know, hard set into the chip itself. C2D cpus are a bit of new breed, for the first time, Intel has left downward CPU multipliers unlocked. Meaning, for example, the E6600 has an intrinsic maximal multiplier of 9—but the bios will also unlock 6, 7, and 8. This is useful in certain circumstances, especially in testing of maximal FSB speed (lower multiplier will allow for higher FSB at the same overall CPU speed ie 2.4ghz = 9 x 267 = 8 x 300 = 7 x 343= etc.). The Extreme Edition CPUs retain their tradition of being both upwards and downwards unlocked.
The Memory Bus
For those of you coming from the older platforms based on DDR SDRAM, you will need to pause a moment and re-orient your thinking. Because of the nature of DDR2 RAM, much much higher speeds are easily achieved.
As a baseline, when running stock FSB speeds, (fastest C2Ds being FSB 267), if you have Ram rated to FSB 267 (DDR2-533 or PC2-4200), the bios will automatically select a CPU:RAM ratio of 1:1.
However, sticks of RAM are commonly available at speeds of FSB 333/DDR2-667/PC2-5300 or even FSB 400/DDR2-800/PC2-6400. Therefore, if you run you CPU at maximal stock FSB 267, but put in these sticks of RAM that are rated much faster, the bios will automatically select a ratio whereby the RAM will be running FASTER than the CPU bus. Currently, these are the selectable RAM ratios and the corresponding RAM speeds:
1:1
FSB 267 (times 1 divide by 1) = 267mhz = DDR2-533 = PC2-4200 Ram
4:5
FSB 267 (times 5 divide by 4) = 334mhz = DDR2-667 = PC2-5300 Ram
2:3
FSB 267 (times 3 divide by 2) = 400mhz = DDR2-800 = PC2-6400 Ram
Even faster RAM modules are out there—(fastest I’ve seen as of writing is FSB 556 = DDR2-1111 = PC2-8888) obviously these are for overclocking as (currently) these are faster than the fastest CPU FSB (267) with the highest RAM multiplier (2:3).
On the one hand, running the Ram faster than the CPU doesn’t give trememdous performance boosts in most settings--on the other hand, if the RAM is rated to do it, that’s free performance.
Memory Latency (and secret settings)
There are many parameters that must be set for RAM to operate appropriately. The most commonly acknowledged settings are:
CAS# Latency
RAS# to CAS# Delay
RAS# Precharge
Cycle Time (Tras)
I list them in this order and as termed because this is how they appear in the very popular and useful program cpu. When not otherwise specified, if you see 4 unlabeled numbers, this is the order they are in. Not all bioses list these in the same order.
Here is how they appear in the AW9D max bios:
Advanced Chipset Features
DRAM Timing Selectable = Manual
X - CAS Latency Time (tCL) = 4
X - RAS# to CAS# Delay (tRCD) = 4
X - RAS# Precharge (tRP) = 4
X - Precharge Delay (tRAS) = 15
Which is in the same order.
The smaller the latency numbers, the faster the RAM turns over data. However, if you tweak them too tight, data will become corrupted. The performance boost from tighter latencies again is not necessarily tremendous in most applications. As a very very rough reference, I’ve generally found that a 10mhz increase in the CPU speed overcomes the performance boost from going from the loosest of timings to the tightest.
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