CMD4GX3M2A1600C8 vs. CMD4GX3M2B1600C8 for 790i Ultra?

The memory finder says that both have been tested with the 790i.

 

Guaranteed-Compatible Memory for your EVGA 132-CK-NF79-A1

 

I plan to set the timings and voltage myself so I dont care about pre-set timings. Which is better? The eVGA 790i Ultra doesnt support either intel XMP or the AMD memory standard so which memory is better for the 790i Ultra, the A or B model? The B model appears to have a newer heat spreader design. Other than that, I cant tell the difference for the 790i Ultra.

It seemed like a simple question...

If you're looking for an immediate response I would suggest calling Corsair directly: 1-888-222-4346

If you're looking for an immediate response I would suggest calling Corsair directly: 1-888-222-4346

 

I did call Corsair. I got an answering machine...

Ok I just spoke to Corsair tech support. They said that for the 790i, the A vs. B model makes no difference. The tech recommended between 1.7V and 1.8V and an SPP of about 2.5. I beleive that I am running the SPP at 2.5 now with the patriot memory. Looks like I was right, the lower voltage on the corsair gives me more wiggle room for tweaking or going up to 8 GB. The patriot gives me no wiggle room at all as it is maxed at 2.0V. I dont think that 8GB will work with the patriot memory at 2.0V.

The memory I chose is actually "optimized" for the AMD Phenom II. The reason I chose the AMD model is that it has the newer DHX+ heat spreader. In truth, there is no difference other than whether a given platform BIOS supports preset memory timings and whether BIOS recogizes the memory and loads the appropriate preset. According to Corsair tech support the underlying memory module is the same and both the Intel and AMD modules are compatible with the 790i ultra. The Corsair Dominator does not support EPP 2.0 but that is not an issue because I will set my own timings anyway. To sum up, as long as corsair says the memory module is certified to be 100% compatible with the 790i ultra, it doesnt matter what platform the module is optimized for, it should work fine with the 790i ultra. Just remember to manually set your timings and voltages in the BIOS. The 790i Ultra had no problems syncing up to the Corsair Dominator once the timings and voltage were set properly.

 

The key is that it runs at the same frequency but at 0.3V lower than the Patriot Viper (2.0V) and uses less power therefore decreasing the load on the Southbridge memory controller. The Corsair seems like very solid, high performance memory and runs at labeled timings of 8-8-8-24 (2T) at the labeled speed of 1600 MHz. The Patriot memory does not run at the labeled timings of 7-7-7-20 (1T) at the labeled speed of 1600 MHz but will only run at 8-8-8-24 (2T). They are about the same price, the Corsair being about $10 more so I think I am going to stick with the corsair. I tried 8GB of Corsair Dominator at SPP 1.45 and Memory Voltage of 1.8V but I got a BSOD (SERVICE_EXCEPTION?) so I backed it off to SPP 1.4 and memory voltage of 1.7V. Seems stable now, I ran 3DMark06 and the score increased by 600 with 8GB RAM. The 3DMark Vantage score was about the same. Vantage seems extremely dependent on GPU performance. I need to run a lot more tests.

I've seen the same results on 790i with the SPP voltage. There seems to be a window for the voltage right at 1.4v or so. Much higher than that and I always got the same results you did unless I was using some exotic cooling on the SPP.

 

IIRC, 1 step above stock on the MCP-SPP voltage seemed to help stability but it's been quite a while since I clocked 790i.

I've seen the same results on 790i with the SPP voltage. There seems to be a window for the voltage right at 1.4v or so. Much higher than that and I always got the same results you did unless I was using some exotic cooling on the SPP.

 

IIRC, 1 step above stock on the MCP-SPP voltage seemed to help stability but it's been quite a while since I clocked 790i.

 

The 2.0V spec on the Patriot Viper is in my opintion way too high to be overclockable much less stable at 8GB on the 790i ultra . 1.65V is a much better starting point for memory installed on an enthusiast board like the 790i Ultra which caps out at a memory voltage of 2.0. I had big problems trying to get 8GB of that "Extreme Performance" memory to be stable on the 790i Ultra. 4GB of it worked fine but I wanted to use all of the memory slots. Given the stability I am experiencing with the Corsair Dominator, I appear to be right in switching memory.

 

Now if I can just get my money back for the Patriot Viper Extreme Performance...

It should be noted that each 2x2GB memory module came as a matched set. If you buy this memory and plan to use 8 GB of it in the 790i Ultra, you should identify the two sets so that you can keep them together. I used a sharpie to label one set of mine. I also installed them in matched slots, ie. one set in the black slots and one set in the gray slots.

I've seen the same results on 790i with the SPP voltage. There seems to be a window for the voltage right at 1.4v or so. Much higher than that and I always got the same results you did unless I was using some exotic cooling on the SPP.

 

IIRC, 1 step above stock on the MCP-SPP voltage seemed to help stability but it's been quite a while since I clocked 790i.

 

Do you think that 1.7V on the Memory Voltage is sufficient for 8GB?

 

I am running an MCP of 1.6V which seems to work fiine. My system is overclocked to 3.6GHz by synching the FSB and memory frequency.

You can go up to 2.0 Volts on these modules but I would try 1.7 Volts for the memory Voltage and if you have more than two modules installed you will want to increase the NB/MCH memory controller Voltage by +.2 Volts as well.

 

The maximum amount of RAM that the 790i Ultra will support is 8 GB. By two modules do you mean 2x2GB is a module or a single 2GB module. The SPP voltage is at 1.4V, thats as high as I have been able to push it. 1.45V is the maximum "green" value or the max that will not risk frying the southbridge.

 

It is interesting to note that when I first booted up with the new Corsair ram, I set the memory voltage to Auto so that the system would boot without resetting the CMOS. The voltage the BIOS chose for the corsair ram was 1.5V. I immediately set that to 1.65V.

A module is one stick.

Thanks for the help. You guys at Corsair rock!

 

What should my "Advanced" memory settings be?

 

tRRD[Auto]

tRC[Auto]

tWR[Auto]

tWTR[Auto]

tFAW[Auto]

tREF[7.8us]

tRFC[Auto]

 

They are currently on auto except tREF is on 7.8us.

Thanks for the help. You guys at Corsair rock!

 

What should my "Advanced" memory settings be?

 

tRRD[Auto]

tRC[Auto]

tWR[Auto]

tWTR[Auto]

tFAW[Auto]

tREF[7.8us]

tRFC[Auto]

 

They are currently on auto except tREF is on 7.8us.

 

I am pretty sure corsair has this information somewhere. Unfortunately, the SPD stops at 1333.

 

Can you please, pelase tell me where to find it?

I cant get tech support on the phone and I cant find the product specs on the corsair website. I think I have found the problem. The CMD4GX3M2B1600C8 appears to be a relabeled 1333 module. Here is the spd:

 

Field Value

Memory Module Properties

Module Name Corsair CMD4GX3M2B1600C8

Serial Number None

Module Size 2 GB (2 ranks, 8 banks)

Module Type Unbuffered DIMM

Memory Type DDR3 SDRAM

Memory Speed DDR3-1333 (667 MHz)

Module Width 64 bit

Error Detection Method None

 

Memory Timings

@ 666 MHz 9-9-9-24 (CL-RCD-RP-RAS) / 34-74-5-10-5-5 (RC-RFC-RRD-WR-WTR-RTP)

@ 592 MHz 8-8-8-22 (CL-RCD-RP-RAS) / 30-66-5-9-5-5 (RC-RFC-RRD-WR-WTR-RTP)

@ 518 MHz 7-7-7-19 (CL-RCD-RP-RAS) / 27-58-4-8-4-4 (RC-RFC-RRD-WR-WTR-RTP)

@ 444 MHz 6-6-6-16 (CL-RCD-RP-RAS) / 23-49-4-7-4-4 (RC-RFC-RRD-WR-WTR-RTP)

 

Memory Module Features

Auto Self Refresh Not Supported

Extended Temperature Range Supported

Extended Temperature Refresh Rate Not Supported

On-Die Thermal Sensor Readout Not Supported

 

Memory Module Manufacturer

Company Name Corsair Memory, Inc.

Product Information http://www.corsairmemory.com/products/xms_home.aspx

 

If I paid a 1600 MHz price for a 1333 module, I am going to be very unhappy. According to Everest Ultimate, that is exactly what I did. The link in the SPD says that this isnt actually a Dominator module but an XMS with a Dominator heat sink. Maybe I am missing something? I wish someone would respond or that tech support would call me back.

I am pretty sure corsair has this information somewhere. Unfortunately, the SPD stops at 1333.

 

Can you please, pelase tell me where to find it?

All of these settings should be left at AUTO or the default settings as they are particular to your memory controller.

 

I cant get tech support on the phone and I cant find the product specs on the corsair website. I think I have found the problem. The CMD4GX3M2B1600C8 appears to be a relabeled 1333 module. Here is the spd:

 

 

 

If I paid a 1600 MHz price for a 1333 module, I am going to be very unhappy. According to Everest Ultimate, that is exactly what I did. The link in the SPD says that this isnt actually a Dominator module but an XMS with a Dominator heat sink. Maybe I am missing something? I wish someone would respond or that tech support would call me back.

The SPD is set to 1333 so that systems can boot for the first time at default settings or after a CMOS clear. This has nothing to do with the actual performance of the module.

 

The specifications are listed on our web page. You need to look under the RESOURCES tab of the page that shows your module.

 

http://www.corsair.com/products/phenomii/default.aspx

CMD4GX3M2B1600C8

Speed Rating

PC3-12800 Tested Speed

1600Mhz Size

4GB Kit (2 x 2GB) Tested Latency

8-8-8-24 Tested Voltage

1.65 Performance Profile

BEMP

SPD Speed

1333Mhz SPD Latency

9-9-9-24 Package

240pin DIMM Fan Included

No

 

All of these settings should be left at AUTO or the default settings as they are particular to your memory controller.

 

The SPD is set to 1333 so that systems can boot for the first time at default settings or after a CMOS clear. This has nothing to do with the actual performance of the module.

 

The specifications are listed on our web page. You need to look under the RESOURCES tab of the page that shows your module.

 

http://www.corsair.com/products/phenomii/default.aspx

 

Thank you for responding. I guess that

 

Memory Speed DDR3-1333 (667 MHz)

 

seemed pretty clear to me but I am not a memory expert. It seems like the SPD should contain settings for 800 MHz?

 

All that really matters is that i cure my instability issues. I am not trying to overclock this memory, just get it stable at 1600.

 

 

 

seemed pretty clear to me but I am not a memory expert. It seems like the SPD should contain settings for 800 MHz?

 

No, you can't set the SPD for 800MHz / DDR1600. You have make BIOS adjustments to run that fast. Motherboard and CPU defaults are 1.5v and either 1066 or 1333 and default voltage on the memory controller. The system would not even post if it's trying to read 1600 which requires 1.65v and in some cases, extra memory controller voltage.

 

We don't have any tested settings for this specific kit on a 790i board as it has not been tested on 790i. Try 1.75v on the memory and 1.4v or 1.45v on the memory controller.

No, you can't set the SPD for 800MHz / DDR1600. You have make BIOS adjustments to run that fast. Motherboard and CPU defaults are 1.5v and either 1066 or 1333 and default voltage on the memory controller. The system would not even post if it's trying to read 1600 which requires 1.65v and in some cases, extra memory controller voltage.

 

We don't have any tested settings for this specific kit on a 790i board as it has not been tested on 790i. Try 1.75v on the memory and 1.4v or 1.45v on the memory controller.

 

According to the Everest chipset properties

 

Supported Memory Types DDR3-800 SDRAM, DDR3-1066 SDRAM, DDR3-1333 SDRAM, DDR3-1600 SDRAM

 

The 790i Ultra does support 1600 MHz memory. I will try 1.75V. I am currently running 1.7V. The Northbridge Voltage is 1.45V.

According to the Everest chipset properties

 

 

 

The 790i Ultra does support 1600 MHz memory. I will try 1.75V. I am currently running 1.7V. The Northbridge Voltage is 1.45V.

 

I'm aware of the board specifications and of what Everest is going to say about the SPD info. The SPD info is not relevent here.

 

Keep in mind a few things.

 

Even though Nvidia states "supports" 1600, 1600 is in fact OCing. OCing is NEVER fully guaranteed.

 

This memory has not been validated at 1600 on this platform so you are entering ucharted territory. It "should" work but there is no guarantee because we have not tested it on boards that are made with discontinued chipsets.

 

The board info states up to 8GB and 1600. But, it is not likely that you will get 4 modules of any density to run 1600 on this board. It should run 8 modules and it should run 1600 with the right memory but it cannot do both at the same time.

I'm aware of the board specifications and of what Everest is going to say about the SPD info. The SPD info is not relevent here.

 

Keep in mind a few things.

 

Even though Nvidia states "supports" 1600, 1600 is in fact OCing. OCing is NEVER fully guaranteed.

 

This memory has not been validated at 1600 on this platform so you are entering ucharted territory. It "should" work but there is no guarantee because we have not tested it on boards that are made with discontinued chipsets.

 

The board info states up to 8GB and 1600. But, it is not likely that you will get 4 modules of any density to run 1600 on this board. It should run 8 modules and it should run 1600 with the right memory but it cannot do both at the same time.

 

I beg to differ. I have in fact achieved what was deemed to be impossible on the 790i Ultra:

 

1600 MHz FSB Frequency

1600 MHz Memory Frequency

8GB Memory @ 1.7V

Auto CPU Voltage

1.3V FSB

1.45V SPP (Northbridge)

1.6V MCP (Southbridge)

QX9650 CPU CPU Multiplier 9X or 3.6GHz overlcok

2x Gigabyte GTX 260 Super Overclock SLI

2x Corsair 4GB (2x2GB) CMD4GX3M2B1600C8 Installed as Matched Sets, one set in the Black slots and one set in the Gray slots.

 

I have so far run the following tests on this configuration:

 

Test runs so far (with 8GB Corsair Dominator):

 

Prime95 64-bit Passed!

OCCT 64-bit Passed!

IntelBurnTest on Standard 64-bit Passed!

3DMark06 19000 3D Marks

3DMark Vantage 23500 3D Marks

 

I have also run World of Warcraft on high settings at 1920x1200 for several hours. I am very pleased with the results so far. I will say that heat is always an issue, with the chipset, video cards and CPU. You should keep the ambient temperature of the CPU as low as possible, I would suggest 75F or lower, this keeps my system rock solid stable. However, if the ambient temperature drifts too high, things start to overheat after several hours of gameplay.

 

Please read this before attempting to 8GB at 1600/1600 on the 790i Ultra

 

http://www.evga.com/forums/tm.aspx?high=&m=41149&mpage=5#74870

 

It should be noted that I did NOT overclock the Corsair memory, it is running at factory specs of 1600 MHz, 8-8-8-24(2T) and with the voltage suggested by Corsair's outstanding tech support, 1.7V.

AWESOME! You have a strong memory controller on that board apparently. Just make sure it is well cooled since you have bumped the voltage.

AWESOME! You have a strong memory controller on that board apparently. Just make sure it is well cooled since you have bumped the voltage.

 

The Alienware P2 chassis has 4 huge case fans, 1 in front, 2 on the side, one in the rear. The Chipset has a huge heat sink and fan on it, the cpu is liquid cooled. As I said above, keeping the ambient temperature down is essential. I will be keeping it at about 70-75 F from now on while gaming.

 

I need to give credit where credit is due. I failed to achieve this milestone using Patriot Viper 1600 MHz EPP 2.0 memory but succeeded with Corsair Dominator DHX+.

 

Great memory Corsair!