Same 7950 card works great on one motherboard, sucks on another one.

[B.T.Coin]

I bought a 7950 card to try mining and I put it in my own PC to give it a test. Everything worked great and I want to build a dedicated mining rig.
So I ordered an Asus F2A55M-LE motherboard with an AMD A4-5300 CPU (or APU as they call it).
When I install the SAME 7950 card on this motherboars and I use the SAME config file for cgminer, it will not work
First I get the error "Maximum buffer memory device 0 supports says 536870912, Your scrypt settings come to 1422917632"
When I remove my 'thread-concurrency' from the config file, cgminer will work but only up to intensity 13. If I put the intensity higher I just get hardware errors. On the other motherboard I could run at intensity 20 without any problems.

Does anybody have any clue what's going on?

[Kaepora]

I bought a 7950 card to try mining and I put it in my own PC to give it a test. Everything worked great and I want to build a dedicated mining rig.
So I ordered an Asus F2A55M-LE motherboard with an AMD A4-5300 CPU (or APU as they call it).
When I install the SAME 7950 card on this motherboars and I use the SAME config file for cgminer, it will not work
First I get the error "Maximum buffer memory device 0 supports says 536870912, Your scrypt settings come to 1422917632"
When I remove my 'thread-concurrency' from the config file, cgminer will work but only up to intensity 13. If I put the intensity higher I just get hardware errors. On the other motherboard I could run at intensity 20 without any problems.

Does anybody have any clue what's going on?

Same thing on one of my rigs I set my core at 1008 core and my memory at 699 and 13 intensity and i am now hashing at over 500 you just need to tweak it. Actually on my fast rig with 1000 core and 699 memory I am getting around 540 hashes except it can take over 13 intensity but I leave it a bit low. Increase work size to like 320 or 256 and g-2

[B.T.Coin]

But on my first setup I was getting 630 K/hash (scrypt) and now I'm lucky to hit 300 without any hardware errors so I'm definitely not going to accept that.
Can anyone confirm that this can be a motherboard issue? If yes, I will just buy a decent board.
The first board was an Intel with the H67 chipset, the second (bad) one is and Asus board based on the AMD A55 chipset.
Does anyone know if I will be OK if I buy a new Intel board based on the B75 chipset?

[Kaepora]

But on my first setup I was getting 630 K/hash (scrypt) and now I'm lucky to hit 300 without any hardware errors so I'm definitely not going to accept that.
Can anyone confirm that this can be a motherboard issue? If yes, I will just buy a decent board.
The first board was an Intel with the H67 chipset, the second (bad) one is and Asus board based on the AMD A55 chipset.
Does anyone know if I will be OK if I buy a new Intel board based on the B75 chipset?

Did you try the settings above?

[B.T.Coin]

But on my first setup I was getting 630 K/hash (scrypt) and now I'm lucky to hit 300 without any hardware errors so I'm definitely not going to accept that.
Can anyone confirm that this can be a motherboard issue? If yes, I will just buy a decent board.
The first board was an Intel with the H67 chipset, the second (bad) one is and Asus board based on the AMD A55 chipset.
Does anyone know if I will be OK if I buy a new Intel board based on the B75 chipset?

Did you try the settings above?

Yes, I did try the above settings and you are correct, I can get the hashrate up to 580 with a lot of tweaking.
But knowing this same card will do 630 on another motherboard, I'm not satisfied with 580, especially since I want to add a second card and get my money's worth of hashing power.

I don't mind spending days on tweaking but can anyone explain me why different motherboards behave so differently?
When I understand why things happen, it's much easier to solve the problem.

Any insight would be much appreciated.