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RAM - Memory Technology Overview
RAM  -  Memory Technology Overview
Date: September 28th, 2004
Topic: Memory
Manufacturer: Various
Author: Jarred Walton
 
 


Introduction

If you have ever asked for advice on what type of RAM to purchase, you were probably given a response that goes something as follows. The higher the supported bandwidth of the RAM, the better, but having lower timings is also important. Both options of course bring along price increases, and buying cheaper "generic" RAM is seldom recommended. The old adage of "you get what you pay for" is often used. This is all sound advice, but what does it really mean? Why is CL2 RAM better than CL2.5 or CL3? What about the other features, like bandwidth? Higher bandwidth is often mutually exclusive to having the best timings, so which is better?

We have planned a series of articles to cover this topic, and in this first part, we will provide a general overview of memory technology and terms, and how they actually affect performance. Specific examples using one type of RAM may be included, but we are saving a detailed comparison of the DRAM types for the next article in this series. For this introduction, we are interested in growing the base of knowledge upon which future articles can be built.

Before we get into the details of memory designs, we would like to simply state up front that anyone who thinks that DRAM technology, design, and implementation are "easy" or "boring" relative to the higher profile CPU and GPU chips is guilty of a gross generalization. While it might be true that an individual DRAM chip is less complex, the memory subsystem as a whole can easily rival other parts for complexity. It should come as little surprise that in a modern PC, system RAM can often cost more on its own than any other component, with the exception of bleeding edge processors and graphics cards. The design problems and solutions can be every bit as interesting - or difficult, if you prefer - as pipelines, execution units, and cache sizes.

Understanding Memory Access   Next Page

 
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22 Comments - Last by 666an666, 190 days ago
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No Subject by IKnowNothing, 1880 days ago
It's like you read my mind. I'm purchasing an Athlon 64 3500+ and wasn't sure if I should purchase generic RAM or high performance RAM.

Cheers.

Reply
No Subject by ariafrost, 1880 days ago
Good choice. You really don't want to get generic RAM... it is generally slow, unstable, and gives you the much-hated BSOD... I've only bought CAS 2 RAM (Corsair XMS) but I may consider buying some CAS 2.5 if the price delta isn't too great.

Reply
No Subject by mino, 1880 days ago
#2 You are missing one important point. That is, unless You can(want) afford at least 512M high quality RAM, it makes NO SENSE to buy 256M DDR400 CL2 since there are 2 basic rules:

1) buy generic memory until your budget could afford no more than 512M DDR400
2) then spend some aditional money for brand memory
3) then go 1G and only at this point spent all additional money for better latencies and so on.

Also do remember that at many shops(here in Slovakia) there is 3 or 4 yrs warranty for generic memory(like A-DATA) and also if you have major problems with compatibility they will usually allow you to choose different brand/type for your board for no additional cost except price difference. Also in case the memory works fine with onother board.
Also Twinmos parts have 99month warranty (for price 10% higher than generic). That speaks for itself.

Except this little missing part of reality,

Goog work Jarred.

Reply
No Subject by mino, 1880 days ago
OK, 3 rules ;) - I added 3rd after some thought.

Reply
No Subject by mino, 1880 days ago
Sry for triple post but some major typpos:
"1) buy generic memory until your budget could afford no more than 512M DDR400"
should be:
"1) buy generic memory until your budget could afford more than 512M DDR400"
and
"Goog"(ROFL) should be "Good"
onother -> another
Hope that's all ;)

Reply
No Subject by Pollock, 1880 days ago
Excellent read!

Reply
No Subject by AlphaFox, 1879 days ago
where are the pictures? ;)

Reply
No Subject by deathwalker, 1879 days ago
I..for one, would rather have 1 GB of CL 2.5 high quality memory than 512 MB of CL 2 high quality memory. I'm conviced that in this instance quantity wins out over speed.

Reply
No Subject by danidentity, 1879 days ago
This is one of the best articles I've seen at Anandtech in a long while, keep up the good work.

Reply
No Subject by Modal, 1879 days ago
Great article, thanks. I like these "this is how the pieces of your computer work" articles... very interesting stuff, but it's usually written in far too complicated a manner for a relative novice like me. This was quite readable and understandable however; nice work.

Reply
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