4 slots for memory?

[siddy5]

I have 4 slots for memory 2x 2g and 2x1g

the 1g is GDD3-1333 128mx8 1.5v ep I copied from a pic I took when my computer was open, I did not get info from 2g memory, but a scan from crucial gave me this info (DDR3 PC3-12800)
I want to upgrade to a total of 12g using my existing 2x2g and my new (2x4g 2rx8 pc3-12800u)
the reason I ask is that I tried to put in mixed ram a 8g and a 4g pc3L and my computer beeped at me and never booted up, even with old memory put back, I gave to a buddy to look at and he said it booted up fine with the original memory, I told him not to do anything, its up now so I don't want to take any chances. anyone have any info?
this what I have installed now
device type: desktop
Your DX4350 System Specs

Scan Id: 87F0C69431D926C3
Memory:
DDR3 PC3-12800, DDR3 PC3-10600

Memory Type: DDR3 PC3-12800, DDR3 PC3-10600, DDR3 (non-ECC)
Maximum Memory: 16GB
Currently Installed Memory: 6GB
Total Memory Slots: 4
Available Memory Slots: 0
1GB
2GB
1GB
2GB
this what I want to add, REMOVING 2x1g memory
Product Name 4GB Memory 1600 MHz Opti 3010 7010 9010
Product Type RAM Module
Memory Standard DDR3-1600/PC3-12800
Memory Technology DDR3 SDRAM
Memory Size 4 GB
Form Factor DIMM
Memory Speed 1600 MHz
Error Checking Non-ECC
Number of Modules 1 x 4 GB
Number of Pins 240-pin
Signal Processing Unbuffered
Compatibility Dell Optiplex 3010
Dell Optiplex 7010
Dell Optiplex9010

 

[Danbuscus25]

well, the new ram is faster, and that can cause problems. also, your mobo may not support 12gb of ram, or the new ram is a higher voltage than allowed.

 

[siddy5]

well, the new ram is faster, and that can cause problems. also, your mobo may not support 12gb of ram, or the new ram is a higher voltage than allowed.

CrucialScan said (up to 16g)
how can I tell if new memory is higher voltage ? I cant find that information on memory.

 

[Danbuscus25]

can you get into the bios?