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Ahh Sweet Memory

If you have replaced or upgraded your system memory lately, you know it’s not as simple as it was a few years ago, when your choices were either 30-pin or 72-pin modules, usually EDO but occasionally Fast-Page. Now you not only need to pick the right one from an alphabet soup of memory types, but the speed and the PC-XX module standard must match your system board.

In this tip we’ll discuss the most common current choices to help demystify the subject. EDO and Fast-Page are not covered, because they are practically obsolete and if you still have one of those old systems you probably already know everything about it. Here’s the newer stuff:

SDRAM – Synchronous Dynamic RAM
This memory runs in synchronization with the system bus, and it’s been available for a few years now for PI – PIII Pentium machines and AMD K5-K6 systems. It initially came out at 66Mhz, then 100Mhz, and now is at 133mhz. The ‘dynamic’ part just means it needs to be refreshed, unlike the ‘static’ RAM used for CPU cache.

Specifications:

DDR RAM – Double Data Rate RAM
This is modified version of SDRAM that transfers data twice as fast by using both the rising and falling edges of the clock signal. AMD was first to use DDR in their Athlon XP systems, followed by Intel in the early P4s.

Specifications:

RDRAM – Rambus Dynamic RAM
The Rambus memory was designed specifically for Intel Pentium 3 and 4 systems. As its name implies it has its own bus just for memory I/O, which of course means it will only work in a motherboard designed for it. The module is known as a RIMM, for Rambus Inline Memory Module. The Rambus concept initially had some market resistance because of its incompatible design from a single manufacturer and because it benchmarked slower than DDR DIMMs with a comparable bus speed, but it was strongly pushed by Intel and seems to be making a comeback.

Specifications:

Note: Dual channel memories require memory to be installed in pairs of identical memory modules, and vacant memory slots are suppose to have continuity modules installed.

DDR2 – This is a speed enhancement over the original DDR, which maxed out at 400Mhz. DDR2 starts at 400Mhz and can go to 800Mhz and beyond. Physical characteristics of the module are the same for DDR and DDR2.

Specifications:

RIMM4200 / PC1066 –The latest development in Rambus is this version just coming out for newer P4 systems. It has evolved from 2-byte to 4-byte bus width, a clock speed of 533 MHz, and they tell us that we no longer need to install them in pairs.

Specifications:

Well, that’s the latest and greatest in system RAM, at least for this week. Now, if the computer would only remember where I put my glasses ……….

Disclaimer - The Micro 2000 Tech Tip is a free service providing information only. While we use reasonable care to see that this information is correct, we do not guarantee it for accuracy, completeness or fitness for a particular purpose. Micro 2000, Inc. shall not be liable for damages of any kind in connection with the use or misuse of this information.