Filling all 4 slots?

MrBoring · 4 May 2011 at 19:00

Is it generally considered not a good idea to fill all 4 memory slots on a motherboard? Are you less likely to have instability issues if you only use two out of four?

I only ask because I had a lot of problems with lock-ups on my ASUS P7P55ED-E when I first set it up with all four slots filled with identical sticks of OCZ Intel Extreme XMP 1333MHz which went away when I removed two sticks.

I've also seen other threads on here where people with memory problems are asked whether they have all 4 slots filled.

If there is a problem, is it something that is caused by insufficient voltage being shared by 4 sticks and can this generally be overcome by tweaking the voltage up a bit?

mikeyholt · 4 May 2011 at 19:41

Maybe it was just the sticks that were the problem. Did you try those two sticks you removed on their own?

I have no issues with using all slots.

Icm76 · 4 May 2011 at 19:47

I don't think it's an inherent 'problem' as the boards are designed to support 4 sticks of memory. In theory the maximum overclock is limited - more power (+ heat) and work required of the memory controller. Indeed I think if you install the maximum 32GB, Intel P55/H55 limit the RAM to an absolute maximum of 1066Mhz or 1333MHz (can't remember which.) I have an Asus P7H55D-M EVO populated with 4x 2GB (Kingston Hyper X) and it's all stable at 1600Mhz-2000Mhz CL8. However, early on I did have problems with stability when pushing the system continuously for hours with IntelBurnTest. I never quite figured out the issue, but suspected an issue with thermal expansion with heat build up.

There are many reports of stability issues caused by over tightened heatsinks straining the motherboard and causing intermittent problems and unrecognised sticks of memory. Possibly this type of issue is more noticeable with 4 RAM slots populated?

Have you tried alternate pairs together? or tested the sticks individually using memtest?

MrBoring · 4 May 2011 at 20:20

Icm76 said:
Have you tried alternate pairs together? or tested the sticks individually using memtest?

Hi, yes, any pair will work fine but when all 4 were in there was the very occasional lock-up with no apparent cause - well certainly nothing I could repeat. Very odd.

I might try upping the voltage very slightly and seeing what happens? These sticks are supposed to run at anything from 1.5 - 1.6 so I'll try manually setting 1.6 in the BIOS

Thanks for the replies

Yellowbeard · 4 May 2011 at 21:10

Running 4 modules places twice the load on the memory controller. You may need to up the memory controller voltage just a bit to be stable with 4 as the stock setting is for 2 modules.

Icm76 · 4 May 2011 at 21:26

In Asus BIOS the IMC voltage is the memory controller - it's called VTT by Intel and others. That may be the one to increase slightly.

The other thing to try would be setting the memory timings manually. CAS latency is the obvious one to try first, try increasing it by 1 and see if that makes a difference. Then start working through the other settings to see if they can be reduced or need to be increased. A lot of patience may be required to set everything manually.