RAM 3.25GB usable of 6GB after overclocking Q6600 to 3.60GHz

The only other memory settings I can think of to play around with would be the "max memory" checkbox in msconfig/boot/advanced options and maybe a BIOS setting for memory mapping.

That and swapping the sticks around in the slots.

I suppose the fact that you don't have 4 identical sticks could mean something as well.
 

My Computer My Computer

At a glance

Windows 7 Home Premium SP1, 64-bitIntel Skylake i5-6600K, not overclocked8 GB HyperX DDR4-2666 (2 x 4 GB)none; graphics are integrated on CPU
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Ignatz Special; 4 speed manual gearbox; factory air conditioning; one of one
OS
Windows 7 Home Premium SP1, 64-bit
CPU
Intel Skylake i5-6600K, not overclocked
Motherboard
AsRock Z170M Extreme 4, micro ATX
Memory
8 GB HyperX DDR4-2666 (2 x 4 GB)
Graphics Card(s)
none; graphics are integrated on CPU
Sound Card
onboard: Realtek ALC1150; external: USB Behringer UF0-202
Monitor(s) Displays
Dell S2340M 23 inch IPS
Screen Resolution
1600 x 900
Hard Drives
System: Crucial MX100 series SSD, 128 GB;
Data: Samsung Spinpoint 103SJ, 1 TB;
Backup: WD Caviar Green WD30EZRX-00D8PB0, 3 TB
PSU
Rosewill SilentNight 500 watt fanless, semi-modular
Case
Antec Solo II
Cooling
Noctua NH-U12S; Noctua F12 intake, Noctua S12A exhaust
Keyboard
Microsoft 200 6JH-00001 USB
Mouse
Dell or Microsoft optical wired; USB
Antivirus
Microsoft Security Essentials and Malwarebytes Premium
Browser
Pale Moon
Other Info
All fans PWM; speeds at idle: CPU circa 500 rpm; intake circa 600 rpm; exhaust circa 600 rpm; CPU temps 27 idle and 47 C load in a warm room (27 C/81 F) when running Intel Extreme Tuning Utility stress test.
wow changed a couple of things in the bios... so i changed the system memory multiplier from auto to 2.00B which changed the memory frequency from 667 1000 to 667 800..... now i have the whole of 6GB ram running on my overclocked 3.60GHz
 

My Computer My Computer

At a glance

Windows 7 Professional x64Intel Core 2 Quad CPU [email protected] [email protected]...6Gb (3.25Gb usable)ATI Radeon HD 4870
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Custom Build
OS
Windows 7 Professional x64
CPU
Intel Core 2 Quad CPU [email protected] [email protected] 9.0x400MHz
Motherboard
Gigabyte GA-X48-DQ6
Memory
6Gb (3.25Gb usable)
Graphics Card(s)
ATI Radeon HD 4870
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