FB DIMM RAM only displaying 2GB

Dissociater

Hey guys, wasn't sure who to ask about this. My work computer has 4GB of FB-DIMM RAM installed, but only 2GB are being displayed.

Anyone know why this might be? It's a Dell running XP.

slash000

You're probably running 32-bit XP.

It's possible that 32 bit XP is not recognizing your full 4 gigs by virtue of it being a 32 bit OS (rather than 64 bit), but usually people are able to get at least 3 gigs to show up.

32 Bit WinXp won't ever recognize 4 full gigs of memory since 32 bit OSs can only address 4 gigs total; and with video memory and windows functions taking up a lot of addressable memory, normally you're lucky just to get 3 gigs or just over 3 gigs of RAM to be recognized by 32 bit WinXP.


Here's a question that will help resolve the issue:

Does your motherboard/BIOS detect the full 4 gigs? If so, then it's definitely WinXP-32 causing you to only see 2 gigs. If your mobo's BIOS is only showing 2, then there is another problem at hand (possibly a bad stick, poor seating, etc. etc.).

FyreWulff

Make sure all 4GB are recognized in the BIOS. It's possible one of the sticks is bad and the computer is just ignoring it (which is possible)

Dissociater

It's a 32 bit machine, but it should be showing at least 3 gb I would think, and the video card only has 256 mb of onboard ram so it should be even closer to the 4MB. This isn't a custom build either, it's a Dell supposedly made for business media work.

I'll check the BIOS when I have a chance.

Dissociater

OK, so here's what my BIOS says. I took a screenshot so you could better see for yourselves, as it doesn't really make sense to me.

I installed the latest BIOS when I first noticed this problem. So it's fresh, and not an outdated BIOS issue.



It sees 4 chips at 1 GB each, and I think 4x1 = 4, but it says there are only 2 GB installed. What gives? Does it have something to do with that Memory channel mode?

slash000

I don't know much about FB-DIMM, but from what I read, it works very differently than your standard desktop with dual channel.

What are your options to change for "Memory Channel Mode"?

Don't change it, yet, but what are your options, at least?

Dissociater

When I try and go into the memory part of the menu there it says there are no settings to be changed, and it is just an informational display.

Vulpine

What happens if you remove one stick of RAM from the machine? If the total available in Windows does not change, then it can't be addressing all four sticks correctly (either through faulty RAM, faulty motherboard, or so on).

slash000

But it doesn't really matter what "total available in Windows" has when even the BIOS itself is only showing 2 gigs, but at the same time, recognizes that there are four 1 gig sticks inserted.

It obviously has something to do with FB DIMM, since FB DIMM works totally different than your standard desktop ram.

I'm stumped, for one, but I know next to nothing about FB DIMM.

exoplasm

You should probably call Dell. Assuming it was bought from Small & Medium business rather than Home (most likely) you should get someone in Texas who knows what they are talking about, rather than "Steve" from India who just reads off a script. Note that Indians work for Dell in Texas also, but they probably know what they are talking about or don't do tech support.

It could be a BIOS configuration issue, or the RAM might have to be in different slots (e.g. 1 3 5 7 instead of 1 2 3 4). Dell's workstations and servers have weird configuration requirements sometimes.

psychotix

If the BIOS is only showing 2gb it's a BIOS config issue. FB DIMMS are not the same as normal memory and there are issues you'll need to work with.

As per the 4gb issue in windows. Yes this is true, and part of it is already eaten up by various items so you'll only ever see about 3gb. Key to remember is that if you have a video card that can eat up other items.

I can help with some of this, but you haven't given enough information. FB DIMM boards are always workstation/server grade. How many RAM slots do you have? Open up the case. A lot of workstations have two CPU sockets but only one CPU in there, some have dual banks for memory (one per CPU), which bank is the memory in?