DDR2 PC2 4200 ONLY supported, CAN a PC2 6400 work by any Chance any software anything?

6400 will work but at the 4200 speed. no software changes needed.

it seems to me the only support is your motherboard. you can't install 6400 in a computer using 4200 sorry man>...

PC2 4200 is DDR2 533 and PC2 6400 is DDR2 800. The DDR2 800 may work either by defaulting at DDR2 533 speed or being manually set to DDR2 533 speed. What is the make and model of your motherboard? If it's an OEM board like an older Dell or HP you may be out of luck. In any case make sure you have the latest BIOS version.

Try it. If it works, it works. If it doesn't, eBay or craigslist it.
And find a new vendor.

as "anort3" said the ram will default to 533MHz instead of the 800 MHz that is the 6400. Example: DDR3 @2400 MHz ram cam can run at 1333 MHz so can 800 MHz ram run at 533 MHz ram. You can force slower but not always force over the rated MHz of the ram. Dell or HP has nothing to do with it Take it from some one still running DDR2 PC 6400 and DDR2 PC2 8500 Ram.

Being Dell or HP actually has a lot to do with it since RAM compatibility is written into the BIOS of a motherboard. Many times a newer BIOS revision will only add compatible RAM and do nothing else. Since OEMs have very basic, limited BIOS the board my not be able to read a faster DIMM.

Then why is it on my old 775 socket Acer EG31M ver.1 motherboard, that has max support for PC2 6400 @800MHz ram, I can insert a set of PC2 8500 @1066MHz ram and have it run at PC2 6400 @800MHz just fine?

what I believe you are referring to is most of the time is you can't run the ram past that speed. Example: I can not run the Acer's ram at 1066MHz that the ram is rated for but it WILL run at 800Mhz. What maters is what the Bios is set for for the ram speed. Most bios have setting, Some OEM's severely limit the bios options, but will still force the ram even though it can run faster to run at the max the board can support.

I may have the wrong name for it so please correct me if I am wrong but the ram is programmed with 3 different settings for speed that the bios can read. This is the fuzzy part but I think it is called JEDEC. The manufacture of the ram programs the speeds to this so the bios can read and auto set the ram to a speed. PIC INCLUDED AS PROOF. Many times this is programmed with the missing High end forcing you to manually set the ram speed to its highest settings. My only guess to this is the same ram is used for different speeds but the higher binned models get the sticker saying it can run at a higher speed and to save money and not have to reprogram the JEDEC they just re use the info for the higher clocked ram.



in this PIC you can see the JEDEC has 3 different settings that the bios can choose from. This Ram is a 2x2GB Kingston HyperX T1 series PC2 8500 @1066 but the JEDEC only lists the the top rating for 800MHz.

in this next pic you can see the ram is NANYA tech ram also known as Optima that is a 2x2 PC2 6400 @800MHz set. The Jedec is also programmed with 3 speeds up to 800MHz but this ram is actually the 800 Mhz ram.


In conclusion what maters is what the Bios sets the ram to run at. It does not matter if the ram can run faster, what matters is what the bios has the ram run at for a frequency. If the motherboard only supports PC2 4200 speed ram, you can insert PC2 8500 ram but the ram will not run at the PC2 8500 speed but will be reduced to the PC2 4200 speed.

thanks for reading class dismissed

have you gone into the bios and made sure the ram settings were set correctly? also the timings need to be set correctly as well. if the motherboard tried to default it to the 800MHz you can have this problem also.

I though you might be out of luck with an older OEM board.

Bgunner you are on the right track with that post but you are using the wrong example since there is no such thing as native DDR2 1066. All DDR2 1066 was factory overclocked DDR2 800 thus all DDR2 1066 supported all the DDR2 800 JEDEC standards.

Christop you are incorrect as well. As long as the speed is supported by the BIOS and DIMM slot it will automatically downclock or can be downclocked manually.

Not when it says 4200 only. I do know about down clocking ram. If I am incorrect why did it not work for the op?

Actually, the op never said it DIDNT work. He was merely asking if it WOULD/COULD work (hence the question beginning with 'CAN'). So, every answer saying that the 800Mhz RAM 'CAN' work, is correct. Now whether it WILL work can only be solved by (as someone already stated) trying it. If it doesn't boot initially, I agree with going into the bios and seeing if you can set the timings manually. If I'm correct, most PC2-6400 is set to something like 6-6-6-18, whereas the PC2-4200 would be set to something along the lines of 4-4-4-12 (depending on manufacturer).

That's why I said early on -"just try it"

if the OP doesn't know enough to change the Bios (to the correct) settings then just sticking it in the machine can cause a not working issue. "just try it" does not aPly in this case. The Question IS more like "Can My bios be adjusted to accommodate PC2 6400 RAM."

everything hinges on weather or not there is a bios adjustment to slow down the ram to PC2 4200 speed to make it work.

In my past experiences (especially with OEM computers like Dell, HP, etc), if there is not setting in the bios to manually change the RAM's speed, then the BIOS automatically does so. That may not be the case here, but I'm merely providing the info that I have come across in the past. I believe it has more to do with whether or not the RAM itself supports it. Most 800Mhz DDR2 supports 800, 667, and 533 (PC2-4200), but I HAVE come across RAM that only operates at a single speed (generally older DDR2, like PC2-3200). If that is the case in this situation (which I doubt), then you would be correct. Either that, or his board's bios is so limited that it has no features whatsoever dealing with adjusting the operating frequency of the RAM.

It will work. The speed of your system was limited by the mother board. You bought a faster memory card won't help your system running faster; but it's backward compatible.

Read more info at this link http://www.crucial.com/kb/answer.aspx?qid=4073&link=Answered&Value=Y