RAM speed?

[Ironcat]

Hi Y'all!

Alright, you guys saw my posting for my dream system, but based on some comments I have gotten from you guys and friends, I have a question...

Can someone please (in very plain non computer geek english) explain RAM to me? I thought I had picked some decent stuff but apparently I need to worry about timing, voltage, latency, etc, etc, ad nauseum...

I'd like to know what it is and what it does but I don't have the mind for the complex descriptions.

[.Maleficus.]

Here is the plain English - http://en.wikipedia.org/wiki/Random_access_memory

I didn't read it all but it might also answer the other questions you had.

[xdxforever]

although that link has lots of good info it doesnt include most important things he wants to know. So:
RAM timings:These are the main factor in latency and its good if its low. DDR is good if it has CAS 2 and for DDR2 CAS 3 (4 is good too). CAS is the first number that is listed in timings and has the greatest effect on performance. the other latentcy timings are very negligable in real performance. The only thing you can know from advertised timings is how high quality the chips are. Low timings imply good overclocking (but doesn't guarentee it). You often have to manually set the timings as most MoBos will put up slower ones on auto.
Voltage: its good if memory will default run on lower voltage but you really don't need to be concearned about it. being able to run at high voltages allows for more overclocking.
The only other notable spec of RAM is speed and thats straitforward so i wont go into detail.

[simon275]

The wiki page just says what it is.

Here you go, go nuts its a corsair presentation on ram.

http://www.corsairmemory.com/memory_basics/153707/index.html

For your answer go to the corsair page and click 12, 14 and 19-24.

Latency is dictates how long it takes the chipset (the northbridge) to access one row of data So

While freq is the data rate of the chips. The latency memory dictates the the number of clock cycles it takes to access read and close the memory row or latency. Also the higher the voltage the higher the freq. This would make it appear that the higher the freq the higher the latency this is not the case.

This graph shows how voltage and memory relate.

http://img80.imageshack.us/img80/8917/freqdn6.png


Here is another good source which explians it in more laymans terms

http://www.custompc.co.uk/custompc/features/96794/how-ram-works/page1.html

So the string of numbers given to you as the latency are seperate numbers of clock cycles to perform seperate functions.

This explains why as memory's freq increases so does the latency

http://www.custompc.co.uk/custompc/features/96794/how-ram-works/page6.html (http://www.custompc.co.uk/custompc/features/96794/how-ram-works/page1.html)

The reason why latency decreases as freq increases is much to overly complex to explain just read the above link. But it has to do with buffering and the fact that parts of the ram arent running at the same freq as the rest of it.

Here is a microsoft explination of it

The topic they are talking about is slightly of topic but the basic principle is there


frequency increases, computation time decreases; and memory latency increases as memory device speeds remain constant. This imbalance between full processor speed and the stalls caused by memory latency is why onloading focuses on memory management

So the memory has to play catch up.

http://72.14.253.104/search?q=cache:gF3COqpl3GkJ:https://www.microsoft.co.ke... (http://72.14.253.104/search?q=cache:gF3COqpl3GkJ:https://www.microsoft.co.ke/whdc/winhec/partners/intel05_IOAT.mspx+latency+decreases+as+frequency+i ncreases+%2B+Ram&hl=en&gl=nz&ct=clnk&cd=5&client=firefox-a)

Here is a guide on choosing the right memory for core 2 duo's

http://www.xbitlabs.com/articles/memory/print/core2duo-memory-guide.html

Basically the best DDR2 Ram to choose is DDR2-800 as it has the right balance of freq to latency.

I hope this helps I know it is complicated take some time to read the articles and I hope you will understand.

I need a cold frothy one after that

[intergalacticman]

ddr is cheaper but slower
i would go with DDR2 800
but make sure your motherboard supports it first

[Omega]

ddr is cheaper but slower
i would go with DDR2 800
but make sure your motherboard supports it first

The differences between DDR and DDR2 are much greater than their clock speeds. Their Latencies, capacities in some cases, but mostly pin count.

DDR is, to the best of my knowledge, 184-pin. As others have stated, CAS2 or CAS2.5 is pretty good. CAS3 is kinda meh, while CAS4 or even CAS5 is utterly revolting. Oh, and CAS Latency can go below 2, in fact, GeIL made RAM called "GeIL One" which was CAS1.5 RAM, pretty ****in' awesome, until it was discontinued.

About speed (First off, Pulses/Sec isn't MHz, it's just Hz, because to get 1MHz you need 1000Hz) DDR tends to have the slower clocks, with some of the best ram topping out at about 500MHz.

DDR2, however, is 240pin and has slower CAS latencies. The CAS Latencies of DDR2 are, from what I can see, either CAS4 or CAS5.

DDR2 does, however, have the added bonus of quicker frequencies. From what I can see, DDR2 pretty much starts at 533MHz and goes up -- If i'm not mistaken, even to 1GHz or so.

[crenn]

DDR2 starts from 400MHz, but that's the lowest and generally isn't used due to it being so slow.

[intergalacticman]

true true, ive seen on newegg at least one ghz.
but by speed, i didnt really mean clock speed, but i can see how it was interpreted that way

The differences between DDR and DDR2 are much greater than their clock speeds. Their Latencies, capacities in some cases, but mostly pin count.

DDR is, to the best of my knowledge, 184-pin. As others have stated, CAS2 or CAS2.5 is pretty good. CAS3 is kinda meh, while CAS4 or even CAS5 is utterly revolting. Oh, and CAS Latency can go below 2, in fact, GeIL made RAM called "GeIL One" which was CAS1.5 RAM, pretty ****in' awesome, until it was discontinued.

About speed (First off, Pulses/Sec isn't MHz, it's just Hz, because to get 1MHz you need 1000Hz) DDR tends to have the slower clocks, with some of the best ram topping out at about 500MHz.

DDR2, however, is 240pin and has slower CAS latencies. The CAS Latencies of DDR2 are, from what I can see, either CAS4 or CAS5.

DDR2 does, however, have the added bonus of quicker frequencies. From what I can see, DDR2 pretty much starts at 533MHz and goes up -- If i'm not mistaken, even to 1GHz or so.