Acer Aspire X3300

Hi all,

I'm a (nearly) complete newbe in BIOS moding. I only changed some logos and SLIC years ago.

I have a desktop computer ACER X3300 with very bad memory transfert speed. I'm under 50% of the correct value. Horrible.
The same memory into another computer gives correct results.
I check that with MemTest86+ 4.20

So I flashed to the latest official BIOS.
Nothing better.

I tested ctrl+F1 to see hidden items, but nothing.

I used AMIBCP with the latest BIOS and see nothing hidden.
This BIOS ROM seems not having any settings for memory: no FSB, no voltage, nothing.
Crap.

So...
Is there a reachable way to add the usual settings ?
Or maybe using another BIOS in place of this one ? In the past this was okay but I don't know if current motherbords work correctly with a foreign BIOS.

Acer Aspire X3300
Motherboard = WMCP78M
CPU = AMD Athlon II X2 215 Processor
Memory = DDR3-12800 800 Mhz in dual channel, but recognised as DDR3-8500 533 Mhz by MemTest86+ (in this computer only. Same memory in another computer is okay)

I have around 4100 MB/S of memory transfert rate in double channel, and 3500 MB/S in single channel (8500 MB/S theorical in single channel).