RAM speed differences

Using sticks with different speeds in same machine

[mattglet]

I have a system with a motherboard that only supports DDR2 RAM, and I'm looking to put more memory in it (current has 4gb, looking to go to 8gb). The problem is that the current sticks are DDR2 1066 (PC2 8500), and those sticks are pretty much non-existent now. Can I put in some DDR2 800 (PC2 6400) sticks and expect everything to work fine? Will the 1066 sticks just under-clock to 800, or how does that work?

[J_RaD]

yes it will work, all the ram will slow down to 800mhz.

but i wouldn't mix match diff speed ram in the same system

[mattglet]

but i wouldn't mix match diff speed ram in the same system

Can you elaborate on this a little?

[Leosghost]

Because it will make the system unstable and you'll keep losing data that ought to be in RAM but that the RAM will be "dropping"..Old RAM ( pre DDR ) you could mix stick values without hitting problems ( most of the time ) ..it would total up the megs and run.

DDR Ram isn't so forgiving..you have to upscale all at once ..( sometimes its even better to get it all from the same maker ) ..sell your old RAM sticks..if they are hard to get ..they may be worth more than you paid for them ..and someone with a good machine ( that they don't want to "upgrade the memory on ), but bad or "flaky" RAM on a stick or sticks ..will buy it ..

An image for you ( its way more complex than this but the image will do ) imagine your data is like molasses ..you have a gallon jug ..you push it, or pour it down a pipe that is 6 inches diameter towards other pipes..matched RAM speeds is like having all the others the same diameter , like 4 x 1 and a 1/2 inch ..it will flow smooth ..and come out like it went in ..unmatched RAM speeds is like 2 x 1 inch and 2 x 2 inch ..it wont go down even if pushed the same ..the 2 x 1 inch ones wont keep up ..or the 2 x 2 inch ones will slow down ..and at the other end it will come out uneven ..and from time to time at the entrance to the pipes it will overflow a little..and some will get lost.

It isn't like that ..but you get the picture ..DDR RAM is better to match..if you want to not lose data or have wiggy things happen to the machine ..like occasionally freezing and / or reboots and /or blue screens etc etc ..or even display problems..

[J_RaD]

^ what he said

you want your ram to be all the same speed, with the same timings, from the same maker.

you can mix match same speed, same timings, different maker.... but its not a good idea to stray to far from that.

[JAB Creations]

The slowest speed rated RAM is the speed which all the sticks of RAM will run. If the slowest is DDR2-400 and you have three other sticks that will run at DDR2-1066 then all four sticks will run at 400MHz.

- John

[Leosghost]

No they won't ..( that would be too simple ..they try to..and never quite manage to keep that "drop to lowest" consistent ..so they oscillate between values which are above base level and below highest level ..and they do not do it regularly or predictably ..so it is isn't true "oscillation" ) see what I wrote above...and that is why unmatched RAM machines are unstable and you shouldn't build / force* them ..

*see Frankenbuild..read it in depth ..because I'm sure that I ..and quite probably J_RaD are not going to explain it here ..life is too short ..and you need to know an awful lot of stuff about, and have lots of experience with IT hardware, and more importantly, an understanding of the physics ( at minimum degree level to follow the basics, and doctorate level would be better in order to keep up ) which determines why the RAM doesn't just default to the lowest speed.

[Frank_Rizzo]

Much safer to ditch all the RAM that you have now and purchase new 4 x 2GB, or 2 x 4GB.

As RAM is so cheap (although DDR2 is now higher priced, due to destined to be used for spares only) you are better off just buying 8GB new.

Make sure the sticks are compatible with the motherboard. See if there is a QVL file on the mobo manufacturers site, which will state exactly what brand and type of sticks you should use.

---

For 8GB in UK you should be paying:

DDR2 8500 £160
DDR2 6400 £100
DDR2 5300 £80

DDR3 Dual Channel 12800 £60
DDR3 Dual Channel 10666 £50

[J_RaD]

^ yea thats prob the best idea, buy all new matched ram.


you used to be able to get away with the mix match stuff and not really run into a problem a looonnnggg time ago when ram wasn't so fast. Now that we are running really fast dual chan ram with tight timings and matched chips, you are just asking for blue screens if you do.

[d3vrandom]

Most of the time mix and matching ram speeds works without a hitch. You can even force all the modules to work at the slowest module's speed if they don't do that automatically. You can do this in the BIOS setup menu. REally you have nothing to worry about!

[Leosghost]

Most of the time

[J_RaD]

ha ha ha ha haaaaaaaaa just thought about this thread for all the wrong reasons.

Trying to get someone a free-bee PC out of stuff in my closet, find an old 3.0ghz P4 hook it up, won't boot....try ram in another exact box but 2.6ghz, boots

out of 3 sticks of ram 2 are close 1 is way off

now remember they are ALL DDR400, but 2 have timings close togheter and 1 has timings that are off.

2 sticks worked find mix matched in the 2.6, would boot up with a full 1GB memory, swap the other way off stick in and it would only boot up with 512. get into the OS run CPU ID note all the timings.(not the bios nor the OS would even acknowledge the other stick of mem but CPU ID would show there is something stuck in there but its not working and atleast give me the stats on it)

nothing would work mix matched in the 3.0ghz machine, it was 1 stick at a time. And the crappiest stick would kick the whole system down to 2.4 took the best out of the bunch, manually set my timings, forced DDR-400 stuck the other stick in

wow it finally works.

now im going to cross my fingers and test it for stability!

DON'T MIX MATCH RAM, unless you've got the time knowledge and patience to make it work right, and if this doesn't pass the death test im about to toss at it....no go it won't leave my hands unstable.

if this wasn't a free-bee of parts in my closet i wouldn't have even gone this far. But these parts need to keep on living doing someone else some good!