Memory upgrade on PXI-8105 and PXI-8106 controllers

[reevem]

Hi,

I've recently upgraded the memory of three PXIs; one with a PXI-8105 controller and two with PXI-8106 controllers.  Both the 8105 and 8105 can take a maximum of 4GB (2x2GB) of DDR2-677 (PC2-5300) memory (see links below).  However, on all three systems, both the BIOS and the O/S only see 3.3GB.  Any idea why this might be the case?

I've tried flashing the BIOS (v1.4 on both PXIs), but with no success.

We're using COTS memory (i.e. not bought from NI) but I'd be hard pushed to believe that that is the cause of the problem.

Thanks.

Links;

• Max memory capacity of PXI-8105  https://www.ni.com/en-us/support/model.pxie-8105.html
• Max memory capacity of PXI-8106  https://www.ni.com/en-us/support/model.pxie-8106.html

[Jarrod_S.]

Are these controllers running Windows? If so, this is normal expected behavior. I think it might have something to do with the fact that Windows reserves the rest of the memory for driver addressing (could be totally wrong there). The same thing happens on my Dell desktop PC with 4GB of memory in it.

[reevem]

Hi,

Yes, all three are running Windows (2000 & XP), one is dual boot with RT.

OK thanks - that sounds plausible to me.  Although a bit curious why the BIOS (i.e. pre-boot) only sees 3.3GB.  In any case the memory upgrades have speeded things up.

Thanks.

[Jarrod_S. · Accepted solution]

I am not sure about the BIOS reporting less than 4GB. Here is a blog post which better describes what I was trying to.

[reevem]

Useful link - yes, it looks as though that must be what's going on.  We'll just have to accept the 3.23GB - it's an improvement over before.

Thanks for help.

[Jason_Coigny]

The main reason for that behavior is fire to the fact that your running a 32bit OS. A 64 bit OS would be able to utilize the additional ram, however for XP that is more than enough ram and I would imagine your system is very happy with it.