The latest (and last) bios is 1.1.4. It's here-- www.dell.com/.../DriverFileFormats

JWBOCHARD,  Curious if you got resolution to the issue of total installed RAM not being recognized in BIOS?

I also have XPS 435T 9000 and upgraded to 24GB DDR3, but inconsistent recognition of RAM by different tools:

  - BIOS (A16) reports 16GB installed and 16GB available

  - Windows 8.1 System screen reports:  Installed memory:  24.0GB (16.0 GB usable).

I have reseated the RAM and confirmed the install followed instructions, but no change.

I also confirmed within msconfig utility that "Maximum Memory" option is unchecked. 

Hello:

A old thread I know.

It is correct as you see it in the BIOS. It is a dell "thing" or possibly Windows. Not up to date with Windows 8.1. Windows 7 shows in the performance and information section in control panel, what your memory is used for or allocated.

Find this section in W-8.1 and most likely it will show you that the rest is "available" on demand.

Noticed this on my own Studio XPS 435T-9000 after a rebuild and the installation of A16 BIOS which appears to be BETA in form. I have 8GB of memory, showing that 4GB is available. 4x2GB Micron double rank.

Windows has concentrated on fast boot up times, you see your Dell splash screen barely show on boot is a example.  

On my rebuild, a clean install of Windows, using all Windows 7 drivers. There is not the "thunder" as before, when you light it up at first, but it is fast. The SSD drive makes it happen. Times change.

Hope it helps.

Different versions of Windows limit maximum memory.  See Memory Limits for Windows... on Microsoft's MSDN site for imposed limits.

Also, memory sticks must be in threes and grouped in odd or even slots, per manual, since it's tri-channel memory.