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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Shinobisan - Wednesday, May 22, 2013 - link
This may actually HELP the PC market quite a bit.Two things stalling PC development:
1 No one is making an operating system that requires more power
Win 8 has the same basic system requirements as Vista, which is 6 years old.
At that age, compute power has doubled 3 times.
So a PC COULD be 2x2x2 = 8 times as powerful... but no one is pushing the boundaries.
Think about it.. some are still using Crysis to validate hardware!
(Crysis is as old as Vista... imagine that!)
2 Game developers design to the smallest common factor (Consoles)
While PC compute power has doubled 3 times, Consoles have been stagnant.
The XBox 360 is 8 years old. Again, about as old as Vista!
We need a shake-up. We need someone to stand up and make an operating system and software that uses what we have. A PC system that is 8 times as powerful as anything on the market currently demands. Give us that... and no one will be talking about the demise of the PC anymore.
xTRICKYxx - Wednesday, May 22, 2013 - link
I've heard the complaints of how stagnated visuals have been and I'm sick of it! Sure graphics haven't advanced as much as we thought, but look how far we've come with animation and creating extremely fluid sprites on screen. I would easily take the faces and animations from Halo 4 (console game) over Metro: Last Light because of how well animated and human the characters look in Halo 4. The textures are so much more complex in Metro, but lack compelling animation of facial features.I believe with this new console generation we will see awesome visual increases across the board with more PC games on the way.
Shinobisan - Wednesday, May 22, 2013 - link
Games have been on an increasing visual detail trend, which I enjoy.But... think about the visuals in a basic PC, tablet or phone device.
They are not just stagnated... they are trending backwards.
(And that goes for Apple, Google, and Microsoft)
If anyone else remembers the days of the original windows where Microsoft battled it out with Amiga and Commodore, you remember that each company had their own GUI interface. They were all blocky and 8-bit. And "metro" in Win 8 reminds me of that era. Why do I have an interface that looks like it was designed in 1983? That's 30 years old!
When I start up my PC, I should be greeted with stunning visuals, real time updates of weather and news in novel graphic ways, and a file system that is fun and intuitive in a graphically artistic fashion.
Yes, I know the article was about consoles... forgive me... I'm rattling on about PCs. Carry on then.
bji - Wednesday, May 22, 2013 - link
And when I turn my PC on all I really want is a bash prompt. To each their own :)BSMonitor - Wednesday, May 22, 2013 - link
PC is held back because of the complexity of designing games for infinite combination of hardware platforms/OS.. Yeah, you can make a game with great visuals, but from a profitability stand point there is no way to measure what % of your gamers can actually benefit. Could put a lot of $$ into a game that only a handful of people can enjoy. Simply risky on the PC side to spend a lot of R&D/Game development dollars.The console provides stability and predictability on the hardware side. Day 1, you know the install base is X million of users for Xbox or PS3. And everyone has same hardware.
Shadowmaster625 - Wednesday, May 22, 2013 - link
If it is so obvious then why isnt AMD doing it? Why would they instead opt for a PS4 style design for their own next gen APU? Either way it is still an epic fail. The'yre either throwing their competitor a huge bone, or throwing themselves on the floor. Take your pick.tipoo - Wednesday, May 22, 2013 - link
Or they are just managing costs, since Kinect 2 will be bundled.WaltC - Wednesday, May 22, 2013 - link
Well, between the two, Sony has nailed the 3d-game end of the console business this go-around, imo. Intel, of course, has nothing powerful enough in the igp department to garner this business, so it's no wonder both companies selected essentially the same architecture from AMD. The CoD snippet run at the end of yesterday's demonstration, announced as running in real-time on an xBox one, was extremely telling I thought. First, it did not appear to me to be running @1080P--but possibly @ 480P: the on-screen imagery was definitely low-res, exhibited noticeable pixel aliasing (I was surprised to see it), and seemed to generate a good deal of pixellation that was very noticeable in the scene transitions. It also looked like nobody wanted to show off XB1 rendering in longer scenes where you could really see the frame-rate and get a solid feel for the performance of the game--the whole demo for CoD consisted of one rapid scene transition after another. The rendering problems I observed could all have been caused by a streaming bottleneck--or else by the limits of the hardware (I *hope* it was the immediate streaming because if not then I think Microsoft is going to have some problems with this design.) It was easy to see why the CoD real-time demo was saved for last and was so very brief...;)But, now that consoles are going x86, there's no earthly reason why either Microsoft or Sony could not update the hardware every couple of years or so when new tech hits the price/performance marks they require. Since we're talking x86, there would never be a question of backwards compatibility for their games as it would always be 100%. I think the days of 8-10 year frozen console designs are over. I think that's great news for console customers.
However, depending on whether Sony handles it correctly, the PS4 could walk away with practically everything as Microsoft is building in some fairly heavy DRM restrictions that involve the basic operation of the device--"storage in the cloud," etc. Involuntary storage, it would appear. If Sony comes out with a gaming console that is not only more capable in terms of the standard hardware, but one which is also customer-friendly in that it allows the customer to control his software environment--I think Sony will walk away with it. The people who will wind up buying the xb1 will be the people who aren't buying it as a game console. To be honest, though, set-top boxes are as common as dirt these days, etc. It should be very interesting to watch as this all shakes out...It's great, though--we've got some competition! (I'm not a console customer, but this is always fun to watch!)
hemmy - Wednesday, May 22, 2013 - link
I think most of that first paragraph seems mostly rubbish to me. Sony made a game console, Microsoft made an all-in-one media device. It was well known before the announcement that Microsoft would be showing very little in the way of games yesterday, and they were saving that for E3. 360 games already render @ higher than 480p.jamyryals - Wednesday, May 22, 2013 - link
So you are saying you saw artifacts in a demo through a live stream? Tell me you are joking...As for Sony/Microsoft upgrading console hardware during the current generation, I mean anything's possible, but they would be leaving a lot of customers behind on older hardware. Developers would have to make sacrifices in framerate or quality to achieve compatibility. This places a lot of demands on game developers for testing more environments. Additionally, there's nothing about x86 which makes this upgrade more achievable than on PowerPC architecture. They could have released upgraded consoles if they saw a benefit.