Elmofongo: Is that how it works?
Hardware Authentication is as broad a term as Car is. Usual (or most sensible) method is as follows:
1) You take some pieces of hardware from a machine and get a hash for them. GPU, CPU, Network Card, System Drive, Motherboard are the usual choices, though you can always use others as well. You store those hashes and a hash of them somewhere.
2) When you try to run the game, you check the hash of hashes against the current hash. If the hash is different, you check how many components have been changed, and weigh them accordingly. Changing the system drive may count as 0.5, while the GPU may count as 3.0, and the CPU as 1.5 for example. If the total changes are more than an imposed limit, assume it's a different machine and require reactivation.
3) Have a number of activations available, and a way to increase them. One method is to allow revoking an installation, thus getting back the activation, another method is to have a maximum number of activations left and gain some periodically, like Origin currently uses (5 machines limit, refreshed every 24 hours), or Anno 2070 which started with 5 activations, and would gain one per month, to a maximum of 10 activations (going from memory, may be inaccurate).
So, for a "normal" user that uses a few machines to play his games, and doesn't modify them every week, Hardware Checks are up to a mild annoyance. For a user that does benchmarks and runs the same game on multiple machines per day, Hardware Checks are extremely restrictive.
Then there are of course the "Any change requires reactivation, you have a total of 3" cases, which suck for both normal and weird users. No idea what GTAV will use though.
huN73R: I came across this article where they were testing a Hardline on same rig with different graphic cards and after 5 they were locked out.
There was a thread here on GOG about it, but mostly people chose to ignore the Origin response. So, to add to this, Origin has a limit of 5 machines per 24 hours. If you wish to benchmark a game, thus use more machines, contact support and they will remove said limit. Tell me if you want me to dig up said thread or the response.