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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novastar78 - Saturday, May 25, 2013 - link
I'm curious to see what feature sets each of these GPU's has. These are not the run of the mill APU's that you can buy at the store. These are both custom SoC's and it's my understanding that they may even be from different generations (7000 vs. 8000), similar to how the PS3's RSX was from the 7900 era and the Xenos was around the R600 era (Unified Architecture). Although this would be a much smaller difference here being the same make (AMD) and similar model (GCN).In the end simply measuring CU's may not be enough to determine the true power/quality of the two GPU's.
We may never know as I highly doubt they will easily divulge this info for fear of the outcry (especially from M$ standpoint).
Still i'm very curious...
epobirs - Saturday, May 25, 2013 - link
"The move away from PowerPC to 64-bit x86 cores means the One breaks backwards compatibility with all Xbox 360 titles. Microsoft won’t be pursuing any sort of a backwards compatibility strategy, although if a game developer wanted to it could port an older title to the new console. Interestingly enough, the first Xbox was also an x86 design - from a hardware/ISA standpoint the new Xbox One is backwards compatible with its grandfather, although Microsoft would have to enable that as a feature in software - something that’s quite unlikely."I would disagree. You won't see compatibility with existing Xbox discs but I very much expect a line of original Xbox titles to be offered as download purchases on the new machine. If Nintendo thinks $5 for an NES game running ont he Wii U is reasonable, Microsoft should able to make some good coin on a core set of two or three dozen Xbox titles at $10 each.
As for the 360 library, those should start turning up in HD (well, HD-ier) remakes in about four years as the market ripens for bringing those item back into circulation. This has worked very well for adding value to the PS3 with HD remake collections of PS2 hits. Given the right tools, reworking old IP can be very cost effective.
Some of the best original Xbox titles might get native remakes. We've already had Halo Anniversary and I wouldn't be surprised to see a Halo 2 Anniversary turn up for Xbox One. Jade Empire and the Knights of the Old Republic games may be worth the investment.
RedavutstuvadeR - Saturday, May 25, 2013 - link
Anand Lal Shimpi why did you not mention any thing about the four move engines in the Xbox one and the capabilities of the cloud quadrupling the Xbox ones powerRedavutstuvadeR - Saturday, May 25, 2013 - link
a link to cloud power of XB1news.softpedia.com/news/Xbox-One-Cloud-Makes-the-Console-Four-Times-More-Powerful-355818.shtml
tipoo - Monday, May 27, 2013 - link
iirc the PS4 had similar hardware blocks to the Move engines, just no fancy branding? And the cloud compute thing is a future theoretical, I'll factor it in when it's actually shown to work well. It can't be used for any latency sensitive calculations of course.slickr - Saturday, May 25, 2013 - link
http://i.imgur.com/5WXh32l.jpgjmr99 - Saturday, May 25, 2013 - link
The Xbox 1 (aka PS4 Mini aka PS4 Lite) sure is a colossal disappointment. Microsoft are trying to cut costs and save money in order to create the biggest gap they can btwn selling price and production cost. In other words, the Apple approach: rape your customers. Kudos to Sony for 1152 cores and gddr5.croc123 - Sunday, May 26, 2013 - link
Interesting article in my 'local' rag this AM...http://www.smh.com.au/digital-life/games/how-micro...
JimF2 - Wednesday, May 29, 2013 - link
I won't buy any console that needs an internet connection. It is a huge privacy risk to have a console with a camera that connects to the internet. A console that connects to the internet once per day or once per week has the same privacy risk as a console with an always-on connection.Gamers should boycott Xbox One so the console manufacturers get the message that we won't accept a required internet connection. If a physical disk is inserted in the console, no internet connection should be needed to prevent piracy. The console manufacturers just have to develop a proprietary disk format that can't be copied by Windows, Mac or Linux. It would be fine if gamers who don't want to put a physical disk in the console to prove they own the game are required to have an internet connection. That way, if a gamer wants to prevent game companies from spying on them, they would just swap disks when switching games. If a gamer uses LIVE or they want the convenience of not needing to swap disks, they would provide an internet connection.
TheEvilBlight - Wednesday, May 29, 2013 - link
The PS4's PS3 games are allegedly coming via GaiKai. I'm curious what MS will do for the old stable of games. I wonder if it would be too much to implement other VM's for the Xbox and the Xbox 360; though a VM on an x86 running PPC is likely to suffer severe penalties. It's either state or gaming from the cloud.Alternatively, developers will recompile some of the "best hits" on the 360 and re-release for the Xbox One. I wonder how that would work with the Halo series, but having Gears of War on a faster machine might be fun.