Do I need to upgrade DDR2 Ram in pairs?

Question

I'm running Vista64 on a AMD64 dual core, with only 1GB of ram.

Do I need to install DDR2 ram in pairs?

My Motherboard:

Manufacturer    ASUSTeK Computer INC.
Model   M2N-E SLI
Version 1.XX
Serial Number   123456789000

North Bridge    NVIDIA nForce 570 SLI Revision A1
South Bridge    NVIDIA nForce 570 SLI Revision A1

CPU AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
Cpu Socket  Socket AM2 (940)

Memory Summary  
Maximum Capacity    4096 MBytes
Maximum Memory Module Size  1024 MBytes
Memory Slots    4

Current Memory:

Memory Summary
Maximum Capacity    4096 MBytes
Maximum Memory Module Size  1024 MBytes
Memory Slots    4
Error Correction    None
DRAM Frequency  251.2 MHz
Memory Timings  4-4-4-8 (CL-RCD-RP-RAS)

Device Locator  Slot 1
Manufacturer    OCZ
Part Number OCZ25331024VDC-K  
Capacity    512 MBytes
Memory Type DDR2 (PC2-4300)
Speed   266 MHz (DDR2 533)
Supported Frequencies   266.7 MHz
Memory Timings  4-4-4-8-16 at 266.7 MHz, at 1.8 volts (CL-RCD-RP-RAS-RC)
Data Width  64 bits
EPP SPD Support No
XMP SPD Support No

Device Locator  Slot 2
Manufacturer    OCZ
Part Number OCZ25331024VDC-K  
Capacity    512 MBytes
Memory Type DDR2 (PC2-4300)
Speed   266 MHz (DDR2 533)
Supported Frequencies   266.7 MHz
Memory Timings  4-4-4-8-16 at 266.7 MHz, at 1.8 volts (CL-RCD-RP-RAS-RC)
Data Width  64 bits
EPP SPD Support No
XMP SPD Support No

Answer 1

You can run SIW, it will tell you make and model of your mainboard.

Post this information here ... or look it up at www.crucial.com yourself.

Answer 2

That's primarily dependent on your motherboard. You need to find the specs for your motherboard as it varies widely.

Answer 3

Running in pairs isn't required on any consumer level DDR1 or later system. IIRC it hasn't been required since the p1 or 486 era. If your ram isn't installed in pairs there will be a performance hit because the CPU will spread data across both sticks of ram that is in pairs doubling the transfer rate. On some older controllers you might force all your ram access into single channel mode.

The performance hit from doing this is smaller than what will happen if you run out of ram and are swapping though; and isn't something you're likely to notice outside of benchmarks.

The price difference between buying a single large dimm and a pair of smaller ones is typically negligible, so if you're buying new you should generally go with pairs. But if you have a spare dimm sitting around not doing anything else there's no reason not to install it.