5800 series

its just how AMD defaults the display for their cards

for the ATI 5770 & 5750, GPU-Z states 5700 series. STEAM does the same thing

so there's no way to know the model of the card without opening the case  

well you can look at the specs on GPU-Z and make sure they are at the correct levels

Yeah I thought about that too but I told myself there must be some way that I can see the full model name  

There's three cards in the 5800 series ( HD5830, HD5850 and HD5870) they all use the same Cypress chip so GPU-Z is detecting the Cypress chip but doesn't know which card its in, all it knows is that it must be a card from the 5800 series.

so that's why the model isn't showed in GPU-Z
Thanks !

in cpu-z it shows the model if thats any help  
or at least in mine it shows

that will be great, I'll give it a try  
Thanks !  

I tried CPU-z but nothing seems to work  

does it really matter? you know what you have and gpu-z can tell you if its correct at the right settings

The chip only reports itself as being a 5800, in order to show the model it would need to check stream processors and clock speeds which wouldnt necessarily be accurate like in the 4800 series the 4870 and 4890 were only differentiated by their clock speed, the 4850 was just a slower 4870 with GDDR3 instead of GDDR5, if its not a reliable method its best not to include it for them so no one can complain that they are wrong.