I am looking to up my memory from 512mb(2x128) to 1gb (2x512)
Here's what I think I know about this. Please correct me if I am not clear.
I have a Dell that you cannot change the BIOS on so that means I need a system specific ram. My motherboard supports dual channel ram, so do I need a matched set or can I buy 2 512mb simms? Another thing I think I understand is with needing the so called system specific ram I cannot use the faster stuff?

i think you're confused.

your BIOS has nothing to do with your RAM really. Your RAM is hardware, your BIOS is simply an instruction set (a chunk of software) programmed onto the mainboard that allows you to set and store specific settings related to your mainboard controlling the way it works.

If you are upgrading your memory, you want to stick with identical pairs in two particular cases:

1) Your board is old enough that it requires you to install memory in matched pairs in order to operate
2) You have a newer "dual channel" board that would benefit from having an identical pair (although it's not required for operation)

You fit into #2

You can quite easily change the BIOS settings on your Dell, just hit the F2 key on boot when the DELL logo shows (before the Windows boot screen shows). This will get you into the BIOS on almost any Dell produced in the past 5 years. However, you must understand - BIOS *only* controls things that are soldered onto the mainboard - NOT add-ons you put into the computer (with one or two corner cases).

Here are some common examples of things your BIOS controls:
Built-in sound (enable/disable it)
Built-in video (enable/disable it)
The controller for your floppy drive (a chip on the board)
The controller for your hard drives and CDROM drives (a chip on the board)
The voltage allowed to go to the CPU socket (and subsequently to the CPU)
System time
Power savings for the mainboard (enable/disable it/control how it works)
Built-in network controller (enable/disable it)
The order in which you search drives for something to boot (e.g. floppy first, CDROM second, hard drive third)
Whether it looks at the PCI slot or an AGP slot first to find the primary video source

Some things that BIOS does *not* allow you to control:
How much RAM is in your system
How much space is on your hard drive
What type of RAM is in your system
How fast your processor is
How fast your RAM is


So - to answer your other questions:
RAM (aka Memory) comes in the form of a stick. It's a small little circuit board with chips on it that store data. It comes in several speeds (I'll leave latencies out of this for simplification).

The speed simply dictates how much data you can push and pull from the stick at normal operating voltage. Different mainboards support different maximum data rates for the RAM (push/pull speeds). Some mainboards support speeds that are are slower than others. These numbers are usually given by the manufacturer and, honestly, are guidelines for what they have tested to be *stable*. I emphasize "stable" because with some tweaking, you can often run faster stuff than what they recommend, but weird things can sometimes happen, hence why you should not get hung up on having the fastest of the fast and just get what the manufacturer recommends.

Now, for your computer in particular, I would get a single pair and replace the pair you currently have. If you want a no-frills solution for absolutely compatible RAM (or your money back) purchase it from www.crucial.com - use their Memory finder to find some that they say is suited for your board. Go ahead and get the fastest they have listed if you want. 1GB (2x512) is a great upgrade and will suit you a lot better than the 256MB (2x128) you say you have now. At least, I expect it will.

If you still have any unanswered questions here, please ask. I'll try my best to exlpain how all this works. I realize the way computers work is like rocket science to some people, but it's really not that complex. I could much more easily show you in person, but that's clearly not an option here :D So I'll do what I can to explain online.

Not to hijack this thread, but a related question...

Before I knew of shifty (or crucial.com) I bought 2G of ram (2 x 1G strips) for my Dell 4500. They went in OK and the system "found" 2G of memory (or so it says under "my computer" & the "general" tab)

Later, I learn of crucial.com and run their memory finder survey. It tells me I have 2G of RAM installed, but my computer will only support 1G. I recall reading somewhere that the BIOS in my machine will not support 2G of RAM.

So...I should just be happy with an extra 1G of RAM that my computer can't use or is there a BIOS fix for this or ???

As always, thanks for all your assistance!

Mike

Shifty
Here is a copy of a post on a Corsair memory forum.
"System Select RAM is basically "Plug and Play" and is geared towards Proprietary
systems such as HP, Compaq, Dell ect.
These systems usually don't have the BIOS options to configure any RAM settings.
The System Select line can be a replacement or an addition to the oringinal RAM.

The Vs line, like the XMS line often needs some tweaking which certain systems don't provide, such as timings and voltage."

I was told that my BIOS will not let me do this. I went into my BIOS & under memory there was nothing about timings or voltage. Does this make sense to you? Mike

Okay - one note to make:

When they say "don't have the BIOS options to configure any RAM settings" they mean that pre-assembled computers don't have the ability to change the voltage, speeds or other "tweaks" you can do to juice up the RAM and make it work better. That's all they mean.

In your case, since you can't "overclock" your RAM (you don't have the settings to), don't bother buying expensive overclockable RAM. That would be like dropping a V8 into a Geo Metro or something, it's silly, you're just not going to get all you could out of it or something. Maybe that's a bad analogy.

Just get something that is low-latency if you want something fast. Try to find something that has latency ratings of like 2-2-2, 2-2-2-5 or 2-3-2-5. Low numbers are good when it comes to latency if you're not going to overclock.

Oh - and Mr. Honey - if you don't tell me what kinda computer you got (model number or motherboard product number) I can't help ya man :)

Typically speaking, RAM limitations are actually related to the main set of chips on the board (aka "chipset"). The chipset is usually the limitation, not the BIOS. However, BIOS updates have been known to let you use faster CPU's and more/faster RAM in a stable fashion.

"That would be like dropping a V8 into a Geo Metro or something"
Sounds like that would finally be a decent Geo Metro:cf:
Thanks for the help.

The point to make was ... the internals of the car (tranny, drivetrain, suspension, etc.) wouldn't be able to handle having the weight and power of the V8 if you used it to it sfull potential - so you would literally not be able to get the power out of it that it was capable of by any stretch of the imagination.

Shifty, Is there much real speed diff. between a cas of 2.5 vs 3.0?
Also does the voltage matter?

Well...voltage can matter in the case of your motherboard. Some motherboards specifically only handle 2.5v sticks. Some will handle anything in the 2.4v-2.7v range.

As for CAS latency, that's a tough question. You're probably not going to notice a conceivable difference between the two. I would really go with something with a CL of 2, not 2.5 or 3.0 if you're not planning to overclock your RAM (i.e. your computer doesn't support these overclock features). If you can't do that, go with the 2.5 if you can, otherwise, well, y'know.

This is just my opinion of course. RAM latencies are a controversial topic in some places and there is so much to consider that just giving a straight "yay or nay" answer isn't really feasible :)