With the current wave of Playstation 4 leaks, it is time to spill some of the beans on what we know about the console. The short story is that it completes the AMD clean sweep of all the next gen consoles.
Yes, you heard that right, multiple sources have been telling SemiAccurate for some time that AMD won not just the GPU as many are suggesting, but the CPU as well. Sony will almost assuredly use an x86 CPU for the PS4, and after Cell in the PS3, can you really blame them? While this may point to a very Fusion/Llano-like architecture we hear that is only the beginning.
One reason we haven’t been talking much about this part is that some of the leaks from credible sources are, well, so far out there that they don’t sound believable. With each new leak, those ‘way out there’ ideas seem more and more likely. Are they pie in the sky dreams, or this Sony laying down the law as to who is king of the console business? Six months ago, we would have leaned towards “put down the crack pipe and step away from the EDA tools”, but now we think Sony is trying to take no prisoners this round.
For starters, you have an AMD Fusion type design, and the recently launched but underwhelming Bulldozer, coupled with a GCN/Southern Islands/HD7000 series core is a good start. If you look at the Bulldozer architecture, it does have some really creepy high level similarities to Cell, doesn’t it? SemiAccurate’s sources won’t spill the beans on the exact generation of CPU and GPU that are in the PS4, but we expect it to be a very customized version of an existing or near future design.
So far, so ‘meh’, but Sony isn’t stopping there, and this is what we didn’t want to believe for so long, Sony is going stacking crazy. The leaks all say that there are multiple additions to the core CPU/GPU chip, and they are not on the same die. Actually, given the steady stream of hints surrounding stacking coming from our Japanese speaking moles, the CPU and GPU could very well be on separate, or even stacked dies too. If you look at console economics, the idea is to make a really big and expensive chip that pushes the bounds of manufacturability. You could make two much less expensive chips that don’t push the boundaries nearly as hard, and end up faster than a single chip competitor like Oban.
For the PS3, Sony put two really big and expensive chips in it, and the core Cell didn’t yield well, didn’t perform as intended, and ended up with a core fused off in order to get to market. 5+ years and several shrinks later, it is easy enough to make, yields very well, and is pretty darn cheap to make. Lose your shirt at first, make it up later, and buy yourself added longevity in the process. That basic formula still works, so the PS4 might be a ‘two chip fusion’ design with the intent to weld the two when the technology allows.
If you do that, you need an interposer, something that Intel has been talking about for a while, and recently shown off parts of too. Luckily, if you know where to look, you will see that AMD is behind, but not by much. Given what they are showing off, the tech will be more than ready by any realistic PS4 ship date. With an interposer, you can do things like stack memory on it, and stack a large number low wattage chips.
One of the things that we had heard about the PS4 chip, or should we say PS4 SoC, is that Sony is really keen on the idea of TSVs. The other bit is that they are going to have lots of extras, we have heard about sensors, but that could just be part of the other odd bit, FPGAs. Yeah, there is a lot of weird talk coming out of Sony engineers, and programmable logic, aka an FPGA, is just one of the things. Additional media processing blocks, DSPs, and similar blocks are all part of the concept.
To do all of this, and I do realize how odd it sounds, you would need some monumental memory bandwidth for it not so starve. Sony is known for screwy memory architectures, if you have ever seen PS3 programming documents, you know how much pain a dev has to go through to get bits in the right place at the right time. The PS4 looks to be better in that regard, but far from perfect. Expect stacked memory, and lots of it, all over the aforementioned interposer. I know this sounds crazy, but we have been hearing it for a year plus now, and, well discounted most of it until Paul Demsey got the same story from a Sony CTO.
In the end, it looks like Sony is going to go for the take no prisoners option on the PS4. If you don’t push fab limits that hard, but do push advanced packaging to the limit, you could very well end up with a monster that is simply not manufacturable as a single die. It won’t be cheap, but it will undoubtedly punt a single chip, or a single chip with stacked DRAM, in to the weeds.
Once again, the end result comes down to the age old question of can they make it? On the surface, the answer is yes, but once manufacturing begins, things may not be quite so rosy. The talk from Sony about the PS4 that seemed like so much of a pipe dream last spring seems, well scary realistic right about now. We don’t expect the PS4 before late 2013 best case, 2014 seems much more likely, so things may change a lot before you can buy one.
So in the end, we close with a simple thought, the Playstation 4 is almost undoubtedly an x86 part with AMD graphics too. That is only the very beginning though. If Sony can back up the boasting with real silicon, and the packaging elves can make it in quantity, it should be a game changer, pun intended. Sony is aiming for the moon just like they did for the PS3. Let hope they come closer to the mark this time, game developers could sure use the power.S|A