I am quite literally writing this from my desk at AMD Markham right now; if you're applying for AMD Markham you're going to almost certainly be doing work on their GPU's because this is their primary GPU office (since it is the former office of ATI). I'm doing dev for them, and I would say that the work you can do here is super interesting + you actually make an impact on their final product. The only limiting factor in the work you can do in this job is that unlike working webdev or something like that you need to learn a TON of stuff at this job to really unlock your potential. I am fairly certain I could work here for 5+ years and still not even know half of what there is to learn, so prepare to be humbled