The Xbox One: Hardware Analysis & Comparison to PlayStation 4
by Anand Lal Shimpi on May 22, 2013 8:00 AM ESTMemory Subsystem
With the same underlying CPU and GPU architectures, porting games between the two should be much easier than ever before. Making the situation even better is the fact that both systems ship with 8GB of total system memory and Blu-ray disc support. Game developers can look forward to the same amount of storage per disc, and relatively similar amounts of storage in main memory. That’s the good news.
The bad news is the two wildly different approaches to memory subsystems. Sony’s approach with the PS4 SoC was to use a 256-bit wide GDDR5 memory interface running somewhere around a 5.5GHz datarate, delivering peak memory bandwidth of 176GB/s. That’s roughly the amount of memory bandwidth we’ve come to expect from a $300 GPU, and great news for the console.
Xbox One Motherboard, courtesy Wired
Die size dictates memory interface width, so the 256-bit interface remains but Microsoft chose to go for DDR3 memory instead. A look at Wired’s excellent high-res teardown photo of the motherboard reveals Micron DDR3-2133 DRAM on board (16 x 16-bit DDR3 devices to be exact). A little math gives us 68.3GB/s of bandwidth to system memory.
To make up for the gap, Microsoft added embedded SRAM on die (not eDRAM, less area efficient but lower latency and doesn't need refreshing). All information points to 32MB of 6T-SRAM, or roughly 1.6 billion transistors for this memory. It’s not immediately clear whether or not this is a true cache or software managed memory. I’d hope for the former but it’s quite possible that it isn’t. At 32MB the ESRAM is more than enough for frame buffer storage, indicating that Microsoft expects developers to use it to offload requests from the system memory bus. Game console makers (Microsoft included) have often used large high speed memories to get around memory bandwidth limitations, so this is no different. Although 32MB doesn’t sound like much, if it is indeed used as a cache (with the frame buffer kept in main memory) it’s actually enough to have a substantial hit rate in current workloads (although there’s not much room for growth).
Vgleaks has a wealth of info, likely supplied from game developers with direct access to Xbox One specs, that looks to be very accurate at this point. According to their data, there’s roughly 50GB/s of bandwidth in each direction to the SoC’s embedded SRAM (102GB/s total bandwidth). The combination of the two plus the CPU-GPU connection at 30GB/s is how Microsoft arrives at its 200GB/s bandwidth figure, although in reality that’s not how any of this works. If it’s used as a cache, the embedded SRAM should significantly cut down on GPU memory bandwidth requests which will give the GPU much more bandwidth than the 256-bit DDR3-2133 memory interface would otherwise imply. Depending on how the eSRAM is managed, it’s very possible that the Xbox One could have comparable effective memory bandwidth to the PlayStation 4. If the eSRAM isn’t managed as a cache however, this all gets much more complicated.
| Microsoft Xbox One vs. Sony PlayStation 4 Memory Subsystem Comparison | ||||||||||||||
| Xbox 360 | Xbox One | PlayStation 4 | ||||||||||||
| Embedded Memory | 10MB eDRAM | 32MB eSRAM | - | |||||||||||
| Embedded Memory Bandwidth | 32GB/s | 102GB/s | - | |||||||||||
| System Memory | 512MB 1400MHz GDDR3 | 8GB 2133MHz DDR3 | 8GB 5500MHz GDDR5 | |||||||||||
| System Memory Bus | 128-bits | 256-bits | 256-bits | |||||||||||
| System Memory Bandwidth | 22.4 GB/s | 68.3 GB/s | 176.0 GB/s | |||||||||||
There are merits to both approaches. Sony has the most present-day-GPU-centric approach to its memory subsystem: give the GPU a wide and fast GDDR5 interface and call it a day. It’s well understood and simple to manage. The downsides? High speed GDDR5 isn’t the most power efficient, and Sony is now married to a more costly memory technology for the life of the PlayStation 4.
Microsoft’s approach leaves some questions about implementation, and is potentially more complex to deal with depending on that implementation. Microsoft specifically called out its 8GB of memory as being “power friendly”, a nod to the lower power operation of DDR3-2133 compared to 5.5GHz GDDR5 used in the PS4. There are also cost benefits. DDR3 is presently cheaper than GDDR5 and that gap should remain over time (although 2133MHz DDR3 is by no means the cheapest available). The 32MB of embedded SRAM is costly, but SRAM scales well with smaller processes. Microsoft probably figures it can significantly cut down the die area of the eSRAM at 20nm and by 14/16nm it shouldn’t be a problem at all.
Even if Microsoft can’t deliver the same effective memory bandwidth as Sony, it also has fewer GPU execution resources - it’s entirely possible that the Xbox One’s memory bandwidth demands will be inherently lower to begin with.
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BSMonitor - Wednesday, May 22, 2013 - link
Nexus tablet doesn't have CoD for free..elitewolverine - Thursday, May 23, 2013 - link
no one will make a $1 game with the visuals of CoD, BF2, halo, the list goes on. They would make 0 money.google taking hdtv gaming seriously? They make all their money on ad's, you honestly think people constantly want ads in a video game? And not product placement...ads. Before you matchmake just watching this 30sec video about vagisil...yea right...
Also, what is a few generations? A few is more than 2, 3 generations ago we were at the ps1. 14yrs ago.
Your telling me that its going to take 19yrs for a tablet to have todays graphics of the xbox1? By that time what the hell will the ps5 have or the x5....
The biggest thing the x1 has for it, that every one is forgetting...cloud/azure.
This is huge, so huge time will show just how little the x1 in multiplayer games will need to compute tasks
Majeed Belle - Sunday, September 8, 2013 - link
I think you are putting way too much stake in the cloud especially when we are talking about computing anything graphics or otherwise. People can barely download music on a steady connection right now. Consoles can't even get you solid updates in a timely manner and you are talking about offloading real work over the internet?ok.
Mathos - Wednesday, May 22, 2013 - link
After reading a lot of articles about these two consoles, and their SoC's. There are some things we can extrapolate from this info.Both Systems are based on the same 8core x86 amd64 CPU. Which means the main logic and memory controllers in the APU's are the the exact same. The comment about PS4 being married to ddr5 may not be true, as we all know that the GPU's can also run on ddr3, plus it may be possible that the cpu memory controller is also capable of running ddr5 or ddr3 in either system..
Both systems are using a 256bit memory bus. Being these are x86 amd cpus, that likely points to jaguar using a quad channel memory controller 64+64+64+64=256, which could be good news when they hit the desktop, if they retain said quad channel controller. It would also be nice to see that in AMD's mainstream chips as well.
tipoo - Wednesday, May 22, 2013 - link
GDDR5 is on the PS4 official spec sheet.Kevin G - Wednesday, May 22, 2013 - link
Going with eSRAM is an odd choice. I would have through capacity would have been more important than absolute latency. By merit of being on-die, using eDRAM would have lower latency than external DDR3. If they had chosen eDRAM, they could have had 128 MB on die. That is enough for three 32 bit, 4K resolution buffers. In such a case, I'd have that 128 MB of eDRAM directly accessible and not a cache. Sure, software would need to be aware of the two different memory pools for optimizations but most of that would be handled by API calls (ie a DirectX function calls would set up a frame buffer in the eDRAM for the programmer).The bandwidth figures for the eSRAM seem to be a bit on the low side too. The Xbox 360 had 256 GB/s of bandwidth between the ROPs and eDRAM. With high clock speeds and a wider bus, I would have thought the Xbox One had ~820 GB/s bandwidth there.
I'm also puzzled by MS using DDR3 for main memory. While lower power than GDDR5, for a console plugged into a wall, the bandwidth benefits would out weigh the power savings in my judgement. There is also another option: DDR4. Going for a 3.2 Ghz effective clock on DDR4 should be feasible as long as MS could get a manufacture to start producing those chips this year. (DDR4 is ready for manufacture now but they're holding off volume production until a CPU with an on-die DDR4 memory controller becomes available.) With 3.2 Ghz DDR4, bandwidth would move to 102.4 GB/s. Still less than what the PS4 has but not drastically so. At the end of the Xbox One's life span, I'd see DDR4 being cheaper than acquiring DDR3.
As far as the XBox One's AV capabilities, I'd personally have released two consoles. One with the basic HDMI switching and another with Cable card + tuner + DVR. And for good measure, the model with Cable card + tuner + DVR would also have an Xbox 360 SoC to provide backwards compatibility and run the DVR software while the x86 CPU's handle gaming and the basic apps. If MS is going to go in this direction, might as well go all the way.
Good to see 802.11n and dual band support. With HDMI in and out, I'd have also included HDMI+Ethernet support there as well. Basically the Xbox One would have a nice embedded router between the Gigabit Ethernet port, the two HDMI ports and the 802.11n wireless.
jabber - Wednesday, May 22, 2013 - link
Remember though that the DDR3 in the Xbox will be hardwired directly with no legacy or other PC related stuff getting in the way. This will be optimised DDR3 and not working exactly how its standardised in our PCs.Kevin G - Wednesday, May 22, 2013 - link
The only advantage DDR3 in the Xbox One has over a PC is that it is soldered. This allows for marginally better signaling without the edge connector of a DIMM.kamil - Wednesday, May 22, 2013 - link
That was surprisingly fair, considering a lot of what I've seen since yesterday. Sony tried hard to do what it thought would "improve the gaming experience" and ended up with a lot of social integration and considerably more aggressive hardware. Microsoft didn't really add much to actually playing games (though they do have some cloud-based stuff including game streaming) but has made a play for becoming a full living room experience, with games, live and recorded television, no hassle cable integration, and seemingly several exclusive partnerships. I'm not convinced that core gamers will see much use for those options (though most of the people I know in that group were already PC-focused if not exclusive) or the social things with the PS4, but the raw power would be a nice draw, assuming Sony doesn't accidentally pull a 360 and overheat with any noteworthy extended use.Of course, if the rumors of Microsoft pushing developers toward always-online DRM, included on-console mandatory check-in every 24 hours, fees for pre-owned or shared games, forced hard drive installs, etc. all pan out a lot of people are going to boycott on principle even if they don't buy used games and have great internet.
blacks329 - Thursday, May 23, 2013 - link
I fall in that category of, not buying used games with decent internet (but capped - damn you Canadian duopoly!!) but definitely won't be picking up the X1 if this holds (at least early on).Additionally, I hate paying for XBL and have no intention of doing it going forward, hopefully Sony doesn't follow this route and maintains PS+ as value added and not a requirement for playing games online.