Memory Buying Guide

Memory Buying Guide


Looking to upgrade your PC's memory?
Why upgrade your system memory
Why use Dell memory?
What if you don't have a Dell system?
How much memory do you need?
How can you be sure you purchase the right memory?
How do you install memory?
Another system performance maximizer: Consider upgrading your hard drive or CD/DVD drive.
Interested in memory for digital cameras, PDAs, or printers, or USB Removable Memory?
Dell DDR Memory
Dell DDR2 Memory
Dual-Channel Memory
System memory glossary
Flash Memory Glossary

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System memory glossary

Buffers and Registers: Assist memory processing by commanding control signals in the memory chips. Registers and buffers placed directly on the memory module enable a system to support a greater quantity of modules. Older technologies like EDO DRAM tend to use buffering, and newer technologies like SDRAM tend to use registers.

DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory): A next-generation SDRAM technology, which rivals Rambus and allows the memory chip to perform transactions on both the rising and falling edges of the clock cycle.

DRAM Memory (Dynamic Random Access Memory): Improves the CPU's performance by holding temporary instructions and data needed to complete tasks. DRAM is volatile memory. If power is turned off, all data is lost.

ECC (Error Correcting Code): A feature in memory for high-end systems that detects and reports memory errors without interrupting the other operations of your system. If you do not see an option for ECC memory when searching for your memory upgrade, your system most likely has non-ECC memory and will not support ECC memory. In this case, or if you know that your system is using non-ECC memory, you should upgrade your system with non-ECC memory (standard). If your system has ECC memory, you should choose the upgrade option with "w/ECC" in the part description.

EDO DRAM (Extended Data Out): Introduced in 1995, EDO is similar to FPM but allows consecutive memory accesses to occur much faster. Enabled the CPU to access memory faster than with FPM.

FPM DRAM (Fast Page Mode): Pre-1995 technology, which enabled faster access to data.

Memory Modules:
  • DIMM (Dual In-line Memory Modules):  Memory chips soldered onto a modular printed circuit board, which inserts into a socket on the system board. Opposing pins remain electrically isolated to form two separate contacts.
  • SODIMMS (Small Outline DIMM):  Commonly used in notebook computers; significantly smaller than the standard DIMM.
  • RIMM (Trademarked name for Rambus):  Have fast access times and transfer speed, but generate more heat.
  • SIMM (Single In-Line Memory Module):  Pins on opposite sides of the board are "tied together" to form one electrical contact.

RDRAM (Rambus Dynamic Random Access Memory): A proprietary technology introduced in 1998 that transfers data at speeds not possible with SDRAM. Offers a high-speed feature called "double clocked," which allows operations to occur on both the rising and falling edges of the clock cycle. Has evolved into a niche product in high-end PCs, NT workstations, and game consoles.

SDRAM (Synchronous Dynamic Random Access Memory): Introduced in 1996. Designed to synchronize itself with the timing of the CPU, so that the CPU no longer had to wait between memory accesses. SDRAM modules come in several different speeds depending on the CPU; for example, PC66 SDRAM runs at 66MHz. Today SDRAM is primarily in the low-cost PC and notebook markets; accounts for a significant amount of the units shipped in 2002.

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