Even if the additional rendering power of the PS4's graphics chip isn't quite as pronounced as the raw numbers suggest, lack of bandwidth can be an absolute killer to performance - and that's a big worry for the Xbox One architecture. You can see this by checking out the following video, where we compare the Radeon HD 7790 with the Radeon HD 7850. What's interesting about this comparison is that while the HD 7790 has fewer compute units than the HD 7850 (14 vs. 16), it's clocked higher, to the point where the raw compute potential of both is virtually identical at around 1.8 teraflops - PS4 territory. The difference comes down to bandwidth. The 256-bit memory bus of the HD 7850 offers a massive 60 per cent advantage over the 128-bit HD 7790 interface.
Three games are covered here: Crysis 3, Skyrim and Battlefield 3. The first two games reveal anything up to a 20 per cent performance improvement owing to the additional bandwidth available, but DICE's BF3 reflects the parity in compute power, offering virtually identical performance, suggesting that sans MSAA, the tech isn't hugely reliant on bandwidth. Transplanting those findings across to the next-gen consoles, developers for the Microsoft console have their work cut-out in utilising the DDR3 and ESRAM effectively in matching the sheer throughput of the PS4's memory bus. Getting good performance from the ESRAM is key in ensuring that Xbox One is competitive with the PS4.
