Difference between 3.3V and 5V DIMM'S

[boomerang]

While working on a system for a friends son recently, I noticed jumpers on the mobo for either 3.3V or 5V DIMM modules.

I've done some research, and I am unable to come up with a definitive answer on the difference between these.

I would assume there is some physical difference (notches or such), but then why the jumpers? Obviously this quite old mobo is capable of using either in the same slot with just a jumper change.

Can anyone set me straight on this?

 

[SocrPlyr]

i think 5V dimms are really old and they don't sell them anymore i really can't remember why they needed the extra voltage... leave it at 3.3V becuz you don't wanna fry your current RAM... that wouldn't be go but then again it is cheap now... hehe
oh wait i found it now... old fast page memory (fpm) and i think edo too used the dimm layout (mainly on macs) and they required the greater 5V
i knew it had to do w/ the old memory standards but couldn't remember till i did a search
so unless you are running edo ram in that dimm (man the performance would reek) don't mess w/ it
hop that helped

Josh

 

[SocrPlyr]

ok i just thought of a little more information
most of the first motherboards that supported sdram also supported edo ram... many of them both had the 168pin dimm and 72pin simms but there was really no need for this (except to still be able to use the old simms) becuz they made edo ram that ran in the 168pin dimms but the edo needed more power... thus the reason for the jumper...

 

[boomerang]

That makes sense because this board does have both dimm and simm slots. The jumpers were set at 5V. I reset them to 3.3V. Works both ways, so I'm still not sure if I did the right thing or not.

This is an old PcChips motherboard. It took a good bit of seaching, but I was finally able to identify the model number of the board and download the manual for it.

What was initially concerning me is that someone had installed both simms and dimms. The manual shows that it is supported, so I left it as was.

Thanks for the help.

 

[Mday]

<< What was initially concerning me is that someone had installed both simms and dimms. The manual shows that it is supported, so I left it as was. >>



i don't care what the manual says, i would tell whoever, don't do that.

 

[SocrPlyr]

if you have sdram in there take out the simms and just use the sdram and make sure it is set to 3.3V...
if not i would just get some sdram right now anyways it is soo cheap... (you can try to sell of the simms too...)
just a thought or 2

Josh

 

[boomerang]

My concerns were the same as yours. I know mixing memory types is a no-no. I told his boy that if he had any problems with it to get a hold of me.

This kid is 15 and has to pay for any upgrades to the computer with his own money. So yes, memory is cheap, but still hard earned dollars for a 15 year old.

If he has problems, I have numerous sticks of PC100 I'll just let him have.

 

[SocrPlyr]

ah i c
well i believe it is ok (w/ some mobos... i'm sure it isn't good for stability) to run sdram at edo timings... it is just incredibly slow for the sdram... i ran into a laptop that it's manual said the same thing...