4GB of RAM, but only 2GB usable?

I've done some testing and here are the results:

Slot 1....Slot 2....Slot 3....Slot 4....Result
2GB.......------......2GB.......------.....Works, but 4GB recognized and 2GB usable.
2GB.......------......-----.......------.....Works with only 2GB. (tried with both sticks)
-----.......------......2GB.......------.....Does NOT work, and post beeps indicate "power error" (tried both sticks)
-----.......2GB.......-----.......2GB.......Does NOT work, and post beeps indicate "power error"

Does anyone have any hints to what's happening? Is this a problem with the motherboard, RAM, or Power Supply?

I would try flashing the BIOS.

I already tried updating the bios to Version F4 and loading all of the drivers from the CD. I'll try clearing the CMOS to see if that helps.

just build a cpu, need your advice. im using i7-920 DO, gigabyt x58-ud5, ocz reaper 6gb 1800mhz, windows 7 ultimate 64bit. my windows properties shows 6.00gb (2.00gb usable) & on my task manager it showed 4.00gb reserve hardware, only 2gb of ram functioning. i tried latest bios, tried also unchecked the maximum memory on system configuration, checked also the cpu pins, loosen the bracket on my cpu cooler also.

i tried yesterday putting 1 stick at a time on each 3 white sockets, 1 stick booted windows on all 3 sockets & the 2 sticks didnt boot windows on each 3 sockets. when installed 3 sticks it can see 6gb but only 2gb usable. ocz 6gb set ram have arrangement on putting in the slots? is it a bad ram or i must reinstall windows?

thanks in advance

i have the same problem, have you resolve the problem clearing manually the CMOS?

@oli_826: i just conctact gigabyte and they can't help me... i have GA-P55M-UD2 motherboard and 4 gb ram but only 2 are usable... (64 bit os)
have you chech in msconfig?

Sometimes Win 7 use the reserved memory for add this to the GPU memory.

saint19 - how can i check gpu memory was added? thanks

ciotto - yes in system config. 5x already check & unchecked maximum memory. did you solve your problem? cleared the cmos already.

You can read this

i have sapphire 5770 and it can't use shared memory... (or yes?)

@oli: have u clear CMOS? problem is resolved? i not clear CMOS, but if u say that u resolve it, i will clear cmos immidiatly

I had the same issue with:
GIGABYTE GA-X58A-UD3R LGA 1366 Intel X58
Intel Core i7-920
G.SKILL 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600

What I noticed was that right after powering the system on, I hid the splash screen and noticed that the RAM was only counting up to 4GB. In Windows it said 6GB of RAM (4GB usable). CPU-Z reported 6GB of RAM.

After hours of troubleshooting I followed a tip to check the pins on the socket of the motherboard. I removed the CPU, placed the mobo under a bright light, and noticed one pin was slightly bent to the side. I straightened it with a tiny flat-head jewelers screwdriver and replaced the CPU. After the next reboot, the BIOS counted up all 6GB of RAM and Windows reported 6GB.

Hey!
I had the same problem that you had, or have.... and I tried everything that I could have found in the web.... nothing solved the problem until I did what you describe here. Lets say that u you have DDR3(1) and DDR3(2).... install DDR3(1) in slot 1, if it works shut it down and try DDR3(2) in the same slot. One of them will not work. So I think its the Memory cuz I had the same issue. After I found out that, I went and exchanged them for new ones and guess what. I got 4gb again and a 7.5 on windows expiriense index. I hope this had helped you out.

If you purchased the RAM individually then RMA {return} the RAM for a Matched Set. Further, if the RAM is NOT compatible then you'll get all sorts of oddball problems. Next, if the DIMM slots are damaged then time for a new MOBO.

Q - What Exact RAM do you have? {provide a link}

Also, see the Resource Monitor image below - the key numbers are the Hardware Reserved, Total & Installed. If the Hardware Reserved is above ~20MB {not GB} then you probably have a BIOS or Compatibility issue. You MOBO does not have an onboard GPU that might suck-up 0.25~0.75GB of physical RAM in the form of Hardware Reserved.

For the 'others' here, assuming no compatibly, onboard GPU, Partitions, bad DIMM slots, bent CPU pins, etc - 9/10 it's a DRAM Voltage issue and/or combined with a QPI/DRAM {IMC} Voltage issue(s). Set the DRAM at or slightly above spec IF the DRAM Frequency is set to RATED SPEED. By Default the RAM should run at 1.5v @ 1066 MHz {most systems} per JEDEC specs {SPD}.

Keep in mind it is VERY COMMON with P55 to have bent CPU pins, especially if there's missing RAM and exponentially so with Gigabyte MOBOs. This is a possibility with the OP. The OP might want to clean the DIMM Slots: Isopropyl alcohol - dampen the RAM pins, insert in DIMM slots, clean and repeat, and allow to dry ~5 minutes.

P55 Slots:


Windows 7 Resource Monitor:

i solve this problem

i have notebook Asus X72D and i haved this problem i have 2 X 2GB , its say 4 gb (2gb usable)
all i did is change slots and ,the in start search type msconfig -> boot->Advanced options-> uncheck all number of processors and maximum memory-> ok ->restart comp.. and that is it.....its works,,,,,