4GB Kit (2x2GB) DDR2 Memory RAM Upgrade for Desktop Computer PC2-6400 800MHz Non-ECC Unbuffered
• 256Meg x 64
• Long Dimm 240-Pin
• Non-ECC Unbuffered
This module may be manufactured by Samsung Hynix Micron Elpida Qimonda Infineon Nanya Aeneon or Memory America.This module is in stock and can ship today.
Memory spec terms
If you're not sure if a module is right for your system, use Memory America configurator for a list of guaranteed compatible modules.
NON-ECC/Non-parity — Most desktop and laptop computers take NON-ECC or Non-parity memory.
ECC/Parity — ECC or parity modules look for errors in data and are most often found in servers and other mission-critical applications used by large networks and businesses.
Unbuffered — Most PCs and workstations use unbuffered memory which is faster than registered memory.
Registered/Buffered — Registered or buffered modules delay all information transferred to the module by one clock cycle. This type of memory is primarily used in servers.
Fully buffered — Designed for next-generation servers, features an advanced memory buffer.
CL — CAS (column address strobe) latency, which is the number of clock cycles it takes before data starts to flow after a command is received. Lower CL is faster. Modules with different CL can be mixed on a system, but the system will only run at the highest (slowest) CL.
Component configuration — (For example: 64Meg x 64) Indicates the size of the memory chip components on the module.
Voltage — For example 2.6V. Indicates the power used by the module. The lower the better.
Check the glossary and FAQs for more detailed definitions.
- Return for refund within: 30 days
- Return for replacement within: lifetime
For a return for credit, this item must be returned to Memory America within 30 days of the invoice date for this policy to apply. For a replacement, we offer a Lifetime warranty and support on all memory upgrades. “Return” constitutes receipt of the product by Memory America, and not the mere issuance of an RMA.
The following conditions are not acceptable for return, and will result in the merchandise you have returned to Memory America being returned to you:
- Modules exhibiting physical damage
- Modules that are missing the manufacturer label containing model number, part number or serial number
- Modules that are missing the manufacturer warranty label
DDR2 SDRAM is a double data rate synchronous dynamic random access memory interface. It supersedes the original DDR SDRAM specification and the two are not compatible. In addition to double pumping the data bus as in DDR SDRAM, (transferring data on the rising and falling edges of the bus clock signal), DDR2 employs an I/O buffer between the memory and the data bus so that the data bus can be run at twice the speed of the memory clock. The two factors combine to achieve a total of 4 data transfers per memory clock cycle.
With data being transferred 64 bits at a time, DDR2 SDRAM gives a transfer rate of (memory clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR2 SDRAM gives a maximum transfer rate of 3200 MB/s.
Since the memory clock runs at half the external data bus clock rate, DDR2 memory operating at the same external data bus clock rate as DDR will provide the same bandwidth but with higher latency, resulting in inferior performance. Alternatively, DDR2 memory operating at twice the external data bus clock rate as DDR may provide twice the bandwidth with the same latency (in nanoseconds). The best-rated DDR2 memory modules are at least twice as fast as the best-rated DDR memory modules.
DDR2 DIMMs are not designed to be backward compatible with DDR DIMMs. The notch on DDR2 DIMMs is in a different position from DDR DIMMs, and the pin density is higher than DDR DIMMs in desktops. DDR2 is a 240-pin module, DDR is a 184-pin module. Notebooks have 200-pin modules for DDR and DDR2, however the notch on DDR modules is in a slightly different position than that on DDR2 modules.
Higher performance DDR2 DIMMs are compatible with lower performance DDR2 DIMMs; however, the higher performance module runs at the lower module's frequency. Using lower performing DDR2 memory in a system capable of higher performance results in the bus running at the rate of the lowest performance memory in use; however, in many systems this performance hit can be mitigated by setting the timings of the memory to a lower latency setting.