This started as a reply to one of our newer members to help give him some basic tips on what all the numerous terms on one of the most complicated parts in your PC's hardware, the memory.

Though there are many things I will not cover here, it will explain some of the most comonly misunderstood "Jargon" you may come across, and should help you when it comes time to purchase or upgrade your computer.

Quote: Originally Posted by mrmobeus2001 how can my dad find out his ram phaze???? sorry its something i know nothing about ram, so please can someone help!!!!!

First of all, "RAM" stands for "Random Access Memory" wich means it can be re-written into over and over, in the old days of computing, you might have heard the acronym "ROM" wich meant "Read Only Memory" wich was "Hard Coded" and could not be written over (At least not unless you had a special interface and software)

Ram Size:

Typical PC's made in the last 4-5 years are equipped with anywhere from 256 Megabytes (MB) all the way to 2 Gigabytes (GB)

What do those numbers mean? well...a megabyte of ram means it can store up to 1 million bits of information, and a Gigabyte is equal too 1,000 megabytes!

With the launch of the "Vista" Operating System (64 bit versions..the standard version is only 32bit) and the current generation of motherboards, you will have the ability to fill your PC with up to 32GB of ram and beyond! (IF you can afford it)

Windows XP (32bit version, wich means the "Home, Pro, and Media Center" versions only support up to 4GB's theoretically, but typically can only use around 3GB due to the OS itself reserving some of the resources..."XP 64 Bit Edition" will support over 4GB of ram, but driver support is seriuosly lacking.

Typically a decent name brand memory will set you back 100$ for 1GB (2x512MB sticks) 200$ for 2GB (2x1GB) and most recently they have launched 4GB kits (2x2GB sticks) that will set you back around 370$ for the least expensive kit currently available at NewEgg.

Newegg.com - Once You Know, You Newegg

Ram Speed:

Now this one gets a bit tricky, so I will try and keep it as simple as possible..but that's a tough job!

This is basically a function of your FSB (Front Side Bus) speed. How they calculate it is kinda tricky at first to understand, so bear with me.

I must divert off a bit here and explain how your CPU speed is arrived at.

You have something called a "Front Side Bus" wich is multiplied by a number, commonly reffered to simply as your CPU's "Multiplier"

So..if you have a CPU that runs at 2.0GHZ (2,000MHZ) it would break down like this:

200FSBx10(Multiplier)=2GHZ!!!

You can change the speed of a CPU by raising or lowering these numbers:

300FSBx10=3GHZ
or
200FSBx15=3GHZ


In the old days of computing, if your computers FSB was 200 "MHZ" (Megahertz-1 milion cycles per second) and it is "Linked" to run at a "1 to 1" ratio, then it will also run at 200MHZ.

After a while, they discovered they could make memory read on both the "Up and Down" side of a "Clock" cycle, wich would essentially allow you to double the amount of data you could read and write!

This is what is know today as "DDR" or "Double Data Rate" memory.

Still with me?

So...your memory that is linked to your CPU's FSB that is at 200MHZ, will now "Effectively" run at 400MHZ (2x200MHZ)

And it has only gotten faster as of late...that was in the days when it was just called plain old ""DDR" (Typical speeds were 266, 333, and 400MHZ) within the last few years they have launched DDR-2, wich won't fit in the old style slots of your motherbaord, it has a different pin count, and requires less voltage too.

DDR-2 picks up where DDR (Now refered to as DDR-1) left off speed wise, starting at 400MHZ, but hardly anyone uses memory that slow now. It can come in many different speed grades... 533, 667, 800, and 1066MHZ are the numbers you will commonly find today on DDR-2.

Now this is where things get realy confusing!

A while back on the Pentium 4 CPU's, Intel decide they could "Trick" the memory into running not just at a double data rate, but a "Quad" data rate!

So, even though your FSB speed would still be at 200MHZ, your ram now would be running at 4x this speed! (200FSBx4=800MHZ) if the CPU's FSB speed is kept at a "1 to 1" ratio that is.

In order to allow greater flexability, Intel and AMD both have what they call "Memory Dividers" wich allow you to slow down the speed of the ram, wich was meant to allow you to save memory by purchasing less expensive ram.

On the Flip side, there are also ratio's that act as "Memory Multipliers" but you won't commonly hear them called that, or hear much about them, so I won't get into any detail of that right now.

Here is an example of a typical modern day Intel "Conroe" Core 2 Duo chip

266FSB x4=1066MHZ using a "1/2" divider would allow for ram to run at 533MHZ

Using a "3/4" divider, it would be at 800MHZ

Using no divider, it would run at the full 1066MHZ

Memory Timings:

Now this one is actually more complex in many ways, but the explination I will give is pretty simple!


You will find a bunch of numbers on the memroy stick after the "Speed" of it, these are a rating of it's "Latency", you will often hear the term "Low Latency Ram" when someone is talking about high performance ram.

A typical stick of DDR-2 ram today may be rated CAS 5-5-5-15

What they baiscally mean in the simplest terms, is how many "Clock Cycles" it will take to perform an operation, such as reading, writing, or storing data.

So..if you had memory that was rated at 3-3-3-9, this would be much "Faster" than the number above, because it takes less cycles of the CPU to do the operations.

The first number is known as "CAS" or Column Adress Strobe, I won't get into the boring details of exactly what that means, but just know that it is typically the most important number to look at when judging ram.

So...here are some typical "Timings" you may see:

DDR-1

2-2-2-5 (Very fast)
2.5-3-3-8 (Medium)
3-4-4-8 (Slow)

DDR-2

3-3-3-9 (Fast)
4-4-4-12 (Medium)
5-5-5-15 (Slow)

Now..to bring the "Speed" and "Timings" together, I will add this:

The "Faster" your spin the ram, the longer of a "Pause" it will need to be able to read and write data.


So if you ram is running at a relatively slow speed such as DDR-1 400, it can run stable with some "Tight" (Another term that means "Low Latency") timings like 2-2-2-5 if the chips on them are very high quality...this typically also means "Expensive"

At the same speed, a medium priced set of ram sticks will run the "Medium" speed of 2.5-3-3-6

Inexpensive or "Generic" ram would run at 3-4-4-8


Now..lets step into modern day again...todays FSB speeds are much higher, so you must reaaaaly slow down the timings (Again..this is "Intel" wich uses the "Quad Pump")

So..at the speed of 533MHZ, you won't typicaly see ram ever rated below 3-3-3-8.

When you bump this speed to 800MHZ, you will find they run from 3-4-3-9 for the most expensive ram, all the way to 5-5-5-15 for the budget stuff.

When you reach a "Fast" speed of 1066, they tend to run at 4-4-4-12 through 5-5-5-15

One of the fastest sets of ramyou can buy today is made by OCZ, rated to run at 1150MHZ with timings of 5-5-5-18..this is what someone that "Overclocks" may use, and will set you back a healthy 470$ for 2GB!

Newegg.com - OCZ 2GB (2 x 1GB) 240-Pin DDR2 SDRAM Dual Channel Kit Desktop Memory - Retail

NOTE: I will be revising this a bit and editing it for the next few days, so please bear with me!

Coming soon...Dual Channel Ram, and "PC" ratings (PC2100,PC2700,PC 3200..etc)

awesome info dude, i feel something sticky, don't you?

Quote: Originally Posted by s1ugh34d awesome info dude, i feel something sticky, don't you?

Me too. I probably oughta go clean up.



Awesome guide as always Solid. +rep to ya

Nice article, I concur with the sticky. One thing though, how about putting the names of the timings in?

Sure..like the ones that follow CAS? I can work on updating it tommorow

Excellent read there $Solids$. Thanks for taking the time to put it together.

E

Some more knowledge has been leaked to the minions below :-)
I'm sure this thread will be linked in a few posts :-)

Excellent information Necro, someone sticky this.

I wasn't able to +rep you, I need to "spread it around" a bit first.

Thank you for the info it will help me out. +Rep for you.

I think it needs to be updated with DDR3 info, including how DDR2 relates/compares to DDR3. Like how with DDR timings of 2-2-2-5 were awesome. DDR2 that bumps up a bit, and DDR3 7-7-7-19 is screaming. Of course that DDR is running at 400mhz, the DDR2 at 800, and the DDR3 at 1600. So it is 4x faster than the DDR with only 3.5x slower timings which would make it the DDR3 equivalent of DDR-400 2-2-2-5 RAM.

At least I think that's how it would work....