So i was wondering if it's possible to use 2 of the same GPU's, but one having a bigger memory capacity. For instance, one Radeon 290x 4gb and one radeon 290x with 8 gb. links are to hypothetical graphics cards, respectively. Graphics card one: https://www.amazon.com/XFX-Dissipation-R9-290X-EDFD-512-Bit-CrossFireX/dp/B00HHIPN5A/ref=sr_1_fkmr1_2?ie=UTF8&qid=152895… graphics card 2: https://www.amazon.com/XFX-Double-1000MHz-Graphics-R9-290X-8DFD/dp/B00PCN3I90/ref=sr_1_2?ie=UTF8&qid=1528950442&sr=8-2&k… .
Yes, AMD made that possible years ago, though it's still not ideal.