Test Settings: Lowest Stable Latencies
Because of the previously mentioned "Boot Strap" limitations, we had to select different FSB speeds to test DDR3-1333 and DDR3-1600 data rates. But how could we do that without throwing the rest of our speeds off?
Lacking any 5:3 DRAM to FSB clock ratio required to test DDR3-1333 with an FSB-1600 processor, we instead must compare DDR3-1333 to DDR3-1066 using FSB-1333, and also compare DDR3-1600 to DDR3-1066 using FSB-1600.
Only two CPU speeds correspond to both FSB-1333 and FSB-1600: These are 2.00 GHz CPU clock and 4.00 GHz CPU clock. Since this started out as an overclocking article, the 4.00 GHz speed was selected. The CPU multipliers needed to reach 4.00 GHz at FSB-1333 and FSB-1600 is 12 x 333 MHz and 10 x 400 MHz, respectively.
| Latency Test System Hardware | |
|---|---|
| Motherboard | Asus Maximus Extreme Rev. 2.01G
Intel X38, BIOS 0501 (10/30/2007) |
| Socket 775 Processor | Intel Core 2 Extreme QX9770 "Yorkfield"
(FSB-1600, 45 nm, 3.20 GHz, 12 MB L2 Cache) |
| Hard Drive | Western Digital WD1500ADFD-00NLR1, Firmware: 20.07P20
150 GB, 10,000 RPM, 16 MB cache, SATA/150 |
| Graphics Card | Foxconn GeForce 8800GTX, P/N: FV-N88XMAD2-OD
NVIDIA GeForce 8800GTX - 768 MB |
| Power Supply | OCZ GameXStream OCZ700GXSSLI - 700W |
| System Software & Drivers | |
| OS | Windows XP Professional 5.10.2600, Service Pack 2 |
| DirectX Version | 9.0c (4.09.0000.0904) |
| Platform Drivers | Intel INF 8.3.1.1009 |
| Graphics Driver | NVIDIA Forceware 163.75 |
Since the Asus Maximus Extreme proved instrumental in diagnosing the boot strap issue, it was retained for memory latency testing.
Four-core processors use memory a little more effectively than dual cores and our highest latency test speed of DDR3-1600 matches the highest memory ratio afforded FSB-1600 processors. We used the only FSB-1600 processor available, which was Intel’s Yorkfield-based Core 2 Extreme QX9700.
Game benchmarks are significantly limited by graphics performance, so we included a powerful GeForce 8800GTX from Foxconn.
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One part on page 3 is a bit confusing to me:
"Because cycle time is the inverse of clock speed (1/2 of DDR data rates), the DDR-333 reference clock cycled every six nanoseconds, DDR2-667 every three nanoseconds and DDR3-1333 every 1.5 nanoseconds. Latency is measured in clock cycles, and two 6ns cycles occur in the same time as four 3ns cycles or eight 1.5ns cycles. If you still have your doubts, do the math!"
If I am reading this right, cycle time is the inverse of (1/2)*(DDR Data Rate or 333 for example). So 1/((1/2)*333)=.006006006 which rounds to 6 milli-seconds, not 6 nano-seconds.
Sorry for my confusion, but could someone please clarify for me?
I can not clarify...this is a good article, but im still anoyed at the spelling and punctuation in the articles...Im not one for utmost spelling and punction in informall chatting messaging etc (like this) but i am when its a published article, you wouldnt find a harry potter novel with spelling mistakes in it....
"and DDR3-1600 is called PC2-12800." Its surposed to say, PC3-12800 not...PC2-12800
On the first page mid way down ^^^
Therlian you got it wrong. Generally, period (cycle time) it's the inverse of frequency (clock speed). But as DDR stands for Dual Data Rate, its real frequency is 1/2 of the specified clock speed. What you did wrong it's that you didn't take in account that DDR-333 means a data rate of 333 MEGA-hertz. Because a hertz is the inverse of a second you get: 1/((1/2)*333 MHz)=.006 micro- seconds, which is equal to 6 nano-seconds. Hope I made it clear for you.
I see now danmari. Thanks for pointing that out. I don't know why I didn't think about the 333 being MHz as opposed to Hz.
"I can not clarify...this is a good article, but im still anoyed at the spelling and punctuation in the articles...Im not one for utmost spelling and punction in informall chatting messaging etc (like this) but i am when its a published article, you wouldnt find a harry potter novel with spelling mistakes in it...."
Sorry but when you make THAT many mistakes in your own post, you have no right to talk about spelling mistakes. The mistake you mention is a typo (hitting a wrong key) not a spelling error.
You however manage to spell "annoyed", "informal", and "supposed" wrongly. You also managed to spell "punctuation" wrongly (the second time.. not sure how you can spell it right the first time and wrong the second..)
If you don't know how to spell, then don't flame others for it.
anyone with notes PC2100,PC3200,PC4200,PC5300?
"Intel’s current fastest Front Side Bus (FSB) uses a 1333-MHz data rate"
No, that's not right!
It's 1600MHz (native) for a Socket 775 CPU and socket 771, and if you didn't notice, some people overclock, big time!
Although DDR3 is touted as using 1.50V, several modules use more!
The same is true of DDR2. In this article DDR2 is described as being 1.8V. In my experience most of the modules are 1.9V and some are higher.