Phenom Two X4 940 Be Ram Upgrade

My Phenom II X4 940 BE resides in the Asus M3A78-T Motherboard.

The RAM in this case is two pairs of Corsair TWIN2X4096-8500C5DF.
The "F" is only relevant in that Corsairs RAM cooling fan is included in the kit.


in the Bios, the Command Rate (CR) is set to enabled (not auto) per Corsair. This locks it at 2T.

Voltage is manually set @ 2.1 volts.

RAM frequency is manually set @ 1066 Mhz.

Cass Latency is manually set (5 for this RAM).

RAS# to CAS# Delay (tRCD) is manually set (5 for this RAM).

RAS# Precharge (tRP) is manually set (5 for this RAM).

Cycle Time (tRAS) is left on Automatic.

Bank Cycle Time (tRC) is left on Automatic.


The final key (as suggested by AMD) to getting all 8GB's of this RAM
to run @ 1066 Mhz. resides in setting the RAM to operate in "Unganged" mode.

8GB's will not run @ 1066 Mhz in "Ganged mode w/ this CPU.

4 GB's will run @ 1066 Mhz. in "Ganged" mode.

If you want all 8Gb's to run in "Ganged" mode, just plug it in
and let it default to DDR2 800. I got mine to run @ 4-4-4-12-2T on 2.1 Volts.


A final note: As configured for 1066, it seems overclocking via the FSB is not tolerated by my system.


EDIT (2:51am 9/2/10): Subsequent analysis revealed, as set above, (tRAS) and (tRC) timings default to slower than Corsair rated speeds.
Subsequent testing revealed, these timings can also be manually set to Corsair specified values of 15 and 22 respectively. Diagnostics reveals no errors.

 

The final conclusion is this;

While this 8GB's of RAM can be made to run (and is in and of itself stable) @ 1066Mhz.
It is not recommended. The Phenom II X4 940 BE memory controller is stressed to the
point of causing random blue screens. If you want / need 8GB's let it default to DDR2 800 .

 

To be honest I think that if you require faster RAM you would do better upgrading to DDR3, however this would mean a new Motherboard, so my decision is it's time for a new system, as that's basically what you have if you replace the RAM, CPU, and Motherboard.

But thanks for the thread and the info contained in it I'm sure it will help alot of people when looking at over clocking or upgrading their systems.

 

It wasn't required. Just wanted. I had fun getting it to work. Truth is, I see just a little bit more throughput
running all 8GB's of this CL5 DDR2 1066 in ganged mode @ DDR2 800 4-4-4-12-23-2T with 2.1 volts on my system.

 

Well the truth be known I don't need a new system, don't tell the wife but I want a Motherboard with more options for overclocking, at the moment me dual core 2.5GHz AMD processor runs happily at 2.97GHz but I would like to play with a faster CPU and see how close I can get to 4GHz (Air Cooled Dalo)

 

The AMD 1090T is rumored to do 4Ghz stable on air.

 

This is true but I must admit I was a little disappointed to find out that some intel quad cores have greater processing power.

 

Intel are going back to the way it used to be and 'capping' some of the chips OC potential I read the other day
Not a good move if I am honest as most AMD enthusiasts (myself included) only moved over to the dark side due to the massive overclocking potential of the Socket 775 chips.

I know we are going off topic here and as I have been away for nearly a week I'm still on catch up :lol:

Kojak as for the RAM post (this one :snckr: ) its interesting that the DDR is rated at 2.1V as memory after 2005 I think it is from memory should NOT need to run any higher than this (2.1 should be the maximum limit not the lower)

again this is from my OCZ days so may have changed again since :huh:

 

The spec's for this 1066 are 5-5-5-15-2T @ 2.1 volts. The spec's for Corsairs DHX CL4 DDR2 800 are 4-4-4-12-2T @ 2.1 volts.

The range of memory Vcore adjustment is capped at 2.5 volts on my motherboard.

 

thats what I mean 2.1V is the upper limit for RAM after 2005.
you shouldnt need to run it that high at 'stock' speeds/settings

 

I understand what you're saying.



These 8GB's of CM2X4096-8500C5DF I'm using have "technically" been down-clocked to DDR2 800.

However, I've tightened the timings. This is why I left the voltage set at 2.1 for this RAM.

This voltage is specified for Corsairs DDR2 800 CL4 Quad Channel kit.

 

One further note.

With all 8GB's running at DDR2 800, 4-4-4-12-23-2T on 2.1 volts,
I recently experienced two random blue screens. This is attributed to the CPU memory controller.
Subsequently, I switched from "ganged" to "un-ganged" control of the memory. No more blue screens...