OCZ Reaper HPC 6 GB DDR3 1866 MHz CL 8 Kit 2

OCZ Reaper HPC 6 GB DDR3 1866 MHz CL 8 Kit

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Test Setup

Test System
CPU:Intel Core i7 920
2.66 GHz, 2 MB Cache
Cooling:Noctua U12P 1336 Edition
Kindly supplied by Noctua
Motherboard:Foxcoon Bloodrage X58, BIOS P07
Kindly supplied by Foxconn
Video Card:PowerColor Radeon X800GTO 16 256MB
Harddisk:Samsung P80 80 GB
Power Supply:Deluxe 500W
Software:Windows XP SP2, Catalyst 9.3


Performance & Overclocking

Before We Get Started

The new Core i7 in combination with the X58 is quite different than previous generations of Intel CPU & chipset combinations. The fact that the tri-channel memory controller is on the CPU poses a few unique limitations for memory makers. While we always bench DDR3 between 1.5 V and 2.0 V, this spectrum is not possible with the Core i7. Intel advertises and only guarantees their CPUs with up to 1.65 V on the memory, because the memory controller has now been placed on the CPU die. This means that there is a lot less room for higher clocks and it will be interesting to see how the memory fares at this maximum allowed voltage.

It should be noted that overclocking on the Foxconn Bloodrage is an art of its own. While most boards will only give you options which tend to be within certain specification, the Bloodrage gives you all the choices within the BIOS. This means that you may set something which will make your system not boot, even if the components can take the overclock. One thing you should always watch when OCing an i7 is the fact that the frequency of the onboard memory controller should be set to twice the speed of the memory you are running. This is simply achieved by setting the multiplier twice as high for the controller compared to the memory. The CPU voltage has been bumped to 1.45 V and any automatic fan control turned off, so that the Noctua CPU cooler blows full force all the time. Preliminary testing of our specific Bloodrage and i7 CPU seem to point to a possible base clock of 200 with a CPU speed of 4 GHz. Just to make sure, various other voltages have been tweaked to the maximum to allow the best possible overclock on the i7 920 - in fact we are even pushing the north bridge voltage and the so called "UnCore" voltage into the red numbers, to make sure that the CPU & mainboard are not the ones holding us back.

Base Settings

This section is new and illustrates what settings were used to attain the advertised speed of the memory sample in this review:
  • Base Clock: 186 MHz
  • CPU Multiplier: 20x
  • CPU Speed: 3720 MHz
  • CPU Voltage: 1.55 V
  • CPU VTT (UnCore) Voltage: +300 mV
  • X58 I0H Core Voltage: 1.24 V
  • Memory Multiplier: 10x
These are just what our Foxconn Bloodrage board booted easily with to reach the Base Clock and resulting 1866 MHz memory speed.

Performance


Before we started benchmarking the memory, we fired up CPU-Z to check the SPD programming of the modules. OCZ has placed some very conservative timings in all the slots. It would have been nice to have one of them actually hold the XMP profile, since this memory is geared exclusively toward the i7 platform.

Starting out, we ran the memory at the rated speed of CL7-7-7-21 at 1.65V and 1866 MHz. The memory worked flawlessly out of the box on that setting. Then we dropped the latency down to 5-5-5-15 and checked if it would boot beyond 1333 MHz at all. It managed to run stable at that speed and a bit above that when applying 1.8 V. Sure, that may be more than Intel officially allows, but we go up to 2.0 V to see if there are any improvements. This is the case with the Reaper HPC from OCZ, as a raise in voltage also means a noticeable race in overclockability, managing 1472 MHz at CL5 with 2.0V. This may not sound like much, but try to find any DDR2 that manages that - you won't.

The next step meant pushing the latency up to CL6 followed by CL7. Moving through the voltage increases, we managed 1474 MHz at 1.65V with CL6, keeping within the specifications laid out by Intel, but we were rewarded with a much higher clock speed 1734 MHz at 2.0 V. Using the memory above the 1.65 V mark at CL7 also means that we were able to run it at the intended 1866 MHz with a tighter timing and coming in just shy of the 2000 MHz mark at 1982 MHz with 2.0V.

Relaxing the timings to the advertised CL8-8-8-24 and starting with 1.5V we did not manage to get the advertised speed out of it. This is something most other i7 kits are capable of. It seems that OCZ has chosen to use a well balanced approach - giving you a great overclocking spectrum, instead of going for memory that performs as intended with 1.5 - 1.65 V, but lacks performance increases above that. This is also obvious, as we hit a wall at 2086 MHz at CL8 with 1.9V and more. This is not due to the memory but clearly a dead end for the rest of the system. At this point the CPU was running at 4.18 GHz, well above the 2.66 GHz stock speed. This means that the memory is great for hardcore overclockers going with any type of liquid cooling, as I am sure the OCZ Reaper HPC can go a bit further and should easily break the 2100 MHz barrier at CL8.

We have also benched the memory with CL9, to show the improvements at voltages up to 1.65V for those wanting to push the memory higher, while keeping within the framework given by Intel. Anything above that means that we will easily hit that wall again, making it pointless as CL8 is naturally faster than CL9.




The voltage scaling of the memory kit we received is excellent. Every bump in voltage, even from 1.6 to 1.65V resulted in higher overclockability and the memory continued to exhibit that attribute throughout the latency settings and all the way up to 2.0V. You should keep in mind that your mileage may vary!
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