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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jeffkibuule - Wednesday, May 22, 2013 - link
Both were built to work along side each other. If it were the former, you'd expect to run Office on it (an HTPC is still a PC) and if it were the latter you'd need to quit a game before running any media apps (since the game would demand to use all system RAM available).As such, it really is neither of the scenarios you presented.
Littleluk - Wednesday, May 22, 2013 - link
I think most of the hardware choices are designed with the display device in mind. There is a huge market of 1080p devices and the price point for those is well established. Most households now have one or will have one. Locking in hardware and performance at a set resolution is good for console costs and game developers. (it does worry me a bit whether advances in PC display technology will equate to higher graphics displays in PC games if the rest of the market is set at 1080p... why develop higher res models etc.) Sony going for a bit higher graphics performance could be an advantage someday if display technology changes to utilize the headroom but Microsoft has solid hardware for their target resolution.The hypervisor approach is particularly interesting to me as it might be a window into the future of where MS may take OS development. Virtual machines optimized for particular tasks can give you a faster spreadsheets and higher game fps on the same box by selecting which OS module is running. Is there a plan somewhere to put Office 365 on the Xbox One? Microsoft would like nothing better than to be selling software suites that use MS cloud services across multiple platforms to each and every one of us.
tipoo - Wednesday, May 22, 2013 - link
More power can be advantageous to the same resolution...My Radeon x1650 could run games in 1920x1080, that doesn't mean it can do everything a GTX680 can at the same res.bengildenstein - Wednesday, May 22, 2013 - link
A visual comparison between the games demonstrated in the PS4 and XB1 presentations clearly give the graphical edge to the PS4. PS4 games look distinctly next-gen, and are approaching CGI in fidelity. These are early days, and this comparison is hardly scientific, but it seems to corroborate the stronger, easier to develop for hardware in the PS4.But I think the underestimated feature for the PS4 is the 'share' button on the controller. Game spectating is a big deal, and this gives the PS4 a fan-based advertising engine. Due to the simplicity of sharing video, expect a flood of high-quality PS4 videos to be uploaded to the web, making the PS4 and PS4 games much more visible online. This turns regular players into advertisers for the system which should significantly help its popularity with cool 'look what I did' videos, walkthroughs, and competitions.
I am also very interested to see how Sony uses the second, low-power, always-on processor in the PS4. Certainly it would be possible to include voice-commands ala XB1, but I think that this can open up interesting new uses to keep the system competitive over the coming years.
Flunk - Wednesday, May 22, 2013 - link
I think you're reading too much into presentations that could very well have been 100% pre-processed CGI. I expect that the final games will look quite similar on both.senecarr - Wednesday, May 22, 2013 - link
You might want to check the Xbox One presentation - one the things they mention is that game play share is easy for developers to include because of all the connections to the Azure Cloud computing. So that just leaves a share button, but that is actually horrible compared to Kinect, which be on every Xbox One. Instead of hitting a button in the middle of your controller and losing your momentum in the game, for Xbox One you should just be able to yell, Xbox, start recording game play.BPB - Wednesday, May 22, 2013 - link
I think the PS4 will share to more people. I expect the Xbox One sharing to be either Xbox Live only or the MS universe only. I think Sony's sharing won't be as limited. At least that is the impression I got from the presentations.blacks329 - Thursday, May 23, 2013 - link
PS Eye (Sony's Kinect) will be included with every console as well, this was announced back in February.jabber - Wednesday, May 22, 2013 - link
If these new boxes are more Media than gaming orientated going forward it could mean far shorter life-cycles for them. We could be going to a 3-4 year cycle rather than the current 8 year trend.HisDivineOrder - Wednesday, May 22, 2013 - link
"The day Microsoft treats Xbox as a platform and not a console is the day that Apple and Google have a much more formidable competitor."I'd say the reverse. The day that Apple and Google decide to become competitors to Xbox is the day that Xbox (and Playstation) go extinct. Right now, MS and Sony are getting by because the HDTV efforts by Apple and Google are "experiments" and not taken seriously. Imagine an AppleTV where Apple allows app installations and a GoogleTV that's focused on gaming with decent hardware.
And imagine how low that GoogleTV (for Games) would cost. Imagine it opens up Android and just like that, bajillions of apps descend upon it.
Hell, it's debatable if they even need to bother making more than a streaming device to receive the image from your tablet and/or smartphone to do just that. Really, all Google needs is an AppleTV-like Airplay connection. You can already plug in whatever USB/bluetooth controller you like.
Within a few generations of Google taking HDTV gaming seriously, they could walk all over Sony and MS because while consoles sit and languish for longer and longer periods of time, tablets are constantly evolving year after year, iterating upward in specs at an impressive rate.
How long before even the Xbox One isn't pushing out graphics far enough ahead of a Nexus tablet that people just go with the $100-$200 tablet with the free to $1 games instead?