Upgrade question

[ChrisW]

I currently have 2GB of memory (F2-8500CL5D-2GBPK) installed in my ASUS M4A785-M motherboard. I have two free slots and am thinking about adding 4GB (F2-8500CL5D-4GBPK) for a total of 6GB (3GB per channel). Since these have the same timings and voltage, should I expect a problem with this configuration?

[GSKILL TECH]

The main concern is whether the two kits can work together. I would suggest using DDR2-800 4-4-4-12 2.0V settings first. These settings are easier to configure, it is less stress on the memory controller, and the performance is basically the same, if not quicker.

Full slots of DDR2-1066 can be difficult for any AMD platform, so a good CPU is definitely needed.

Thank you
GSKILL TECH

[ChrisW]

I went ahead and ordered the memory and a new Phenom II x4 955 BE processor. 6GB dual channel works just fine. Here are some benchmarks I made with MaxxMem:
DDR800 5-5-5-15 6.97GB/s
DDR800 4-4-4-12 7.11GB/s
DDR1066 5-7-7-25 6.55GB/s
DDR1066 5-5-5-15 6.57GB/s (had to raise NB voltage to 1.2V)

For some reason, DDR1066 is much slower than DDR800.
Then I tried DDR1000 by raising the HTT to 250, lowering the processor multiplier to x13 to stay at the same speed, then lowering the HT link speed to x8 to stay at 2000 and this is what I got:
DDR1000 5-5-5-15 8.63GB/s

So it seems trying to reach 1066 by overclocking the HT reference clock is the way to go. Setting the memory to 1066 with a processor running at 400 just makes things worse. Also, going from 2GB to 6GB raised my Windows Experience Index from 5.5 to 7.5.

[GSKILL TECH]

somebody knows what they are doing!

Now if only DDR3 users understood this, my job would be much easier.

CPUs are designed for DDR2-800 and DDR3-1333, so to fully utilize high performance memory, you must overclock the CPU to enhance bandwidth. When benchmarking memory, you will notice raising ANY frequency will enhance performance, because it increases bandwidth. The base clock is the reference clock, so raising the reference clock will overclock everything else. You can increase multipliers individually to raise frequencies independently, but most of the time you should raise all anyway, so the reference clock is a good method.

For example, look at our AMD CPU + G.Skill 1600 sticky guide. Notice there is Method #1 and Method #2. There are multiple methods, but as long as the end frequencies are sufficient, the performance will be good.

This is why so many people have a problem with DDR3-1600. They think it is plug and play. Sometimes it is stable, sometimes it is just slow, and people complain, once they figure out how to set it up, they find out the memory is very fast and they just need to set it right.

Then there are those that are ignorant, and still believe they should not need to set anything in BIOS, so they will never get their computer to perform correctly.

Sorry for the extended message, but I am hoping people read this so they can understand and have their computer operating at max performance. That's our main goal, we want everybody to have a fast computer. Performance parts should be used as performance parts; plug and play cheap memory should be used as plug and play cheap memory. Don't get them mixed up!

Thank you
GSKILL TECH

[ChrisW]

I wish I would have known about the DDR3-1600 thread as it would have saved me lots of time researching this myself.
I tried the second method, increasing the NB frequency to 2600MHz and this is what I got:
DDR1066 5-5-5-15 7.24GB/s (had to increase NB voltage to 1.25V)

That is better, but not as good as increasing the HT reference clock.
I also tried increasing the HT reference clock to 265 and this is what I got:
DDR1060 5-5-5-15 9.07GB/s

This is significantly better than method #2 and all voltages remain to their default settings.