Playstation 5 System Architecture Explained

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DecoyOctopusX

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Edited By DecoyOctopusX

With Sony's reveal of the hardware specifications and architecture it's easy to say at a glance, "the specs are lower than the Xbox Series X," and call it at that. Though things are not as simple as they seem. At it's core the Xbox is still basically setup like a PC, but with many things directly attached for faster speeds all around. Though the bottleneck you run into is pushing all of your data through the processor I/O controller before it even hits the RAM, GPU, or anything else it needs to. I had a hard time acquiring any AMD processor technical datasheets so here is one of an Intel i9. The construction of the chips and controllers only vary slightly in terms of actual layout.

source: intel.com
source: intel.com

So as seen here you can see that for a typical PC processor, all the data needs to be routed through one of the system controller chips to get where it needs to go. When trying to process large volumes of data for a game, this creates a bottle neck. Like trying to push too much water through a hose eventually it will back up and cause problems. In the case of a game you have to scale back assets and features until you meat the I/O Controller's bandwidth requirements. Now on to the way the PS5's SoC(System on a Chip) is setup.

source: Sony Road to Playstation 5 Video
source: Sony Road to Playstation 5 Video

In the case of the PS5 there are custom I/O controllers for each place you need to send data. This basically gives you an independent channel of bandwidth for each specific task meaning a programmer can push large amounts of data through to each area simultaneously. This is what will allow developers to eliminate load times, hitching between game sections, etc. Basically instead of one hose to push your water through you now have six hoses, and obviously that equates to a lot more water going where you want. I don't have the details of the Xbox Series X SoC, but considering they mentioned wanting to run more generalized applications and the possibility of installing Windows 10 it seems unlikely Microsoft would take this approach due to the way Memory Access works within the Windows system. If I am correct this means that though the specifications of the PS5 are slightly less, it could still potentially out-perform the Xbox Series X through sheer throughput. Take this all with a grain of salt though, this does not necessarily mean all games will utilize the technology and be able to achieve the same performance as Sony first-party studios. Not every studio has the time, or the budget to invest in the R&D necessary to fully utilize the technology. In the case of Xbox you are basically programming like you would for a Windows 10 PC which is far easier for sure. I guess everyone will eventually see how this plays out though, but PS5 from a hardware and programming perspective is certainly very tantalizing. That is my two-cents on the subject, have a good day everyone!

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zoofame

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#1  Edited By zoofame

I appreciate the effort to simplify and explain things for less technically-inclined readers but this is not really true. The "bottleneck" remarks are being conflated to mean something very different here. In the end I suspect the raw throughput won't matter at all compared to the upgrade both systems have coming from HDDs. Will you notice a game loading in a half second vs 1 second? Probably not. But you will definitely notice 1 second versus 1 minute.

Both systems are running the same AMD hardware architecture. They're customized with different clock speeds and core counts but the SoC is essentially the same with respect to I/O. Both are using SSDs over standard PCIe just like any computer built in the last few years. In that sense there is no dedicated I/O "secret sauce" that Sony is using that MS doesn't have.

The difference in Sony's case is that they built a custom SSD flash controller with higher raw throughput. Xbox X is 2.4 GB/s vs PS5's 5.5 GB/s. With compression, each of those throughput numbers is ~ doubled (obviously depending on the content of that data wrt compressibility). Sony's competitive edge here is using a 12-channel flash controller that can take advantage of the headroom afforded by the relatively recent doubling of bandwidth from PCIe 3.0 to PCIe 4.0. High end consumer PC hardware typically reserves 4 "lanes" of PCIe for internal SSD storage. PCIe 3.0 offers ~ 1 GB/s per lane, so effectively 4 GB/s per drive, while PCIe 4.0 doubles that to 8 GB/s.

All SSDs exploit the inherent parallelism of flash memory chips to increase bandwidth by using multiple channels. It's unclear how many the Xbox X are using internally, but ultimately it's an implementation detail that isn't relevant beyond the fact that XBox has about half the raw throughput at the SSD controller.

Of course, all of this glosses over latency which is the real reason SSDs made HDDs obsolete for anything but cheap, write-once / read-many data. Neither company has provided details regarding IOPS or latency characteristics at different queue depths, which are more applicable to general computing workloads like database servers. It also ignores the type of flash being used and whether there are multiple tiers of cache on the drive, which is an area where PC SSD manufacturers are trying to optimize multiple tradeoffs in performace, write endurance, and cost.

At the high level, I think MS made the right choice with their priorities. Their storage model is already more than good enough for fast load times, as they showed in actual demo footage (which Sony has not). Instead, MS spent their budget on more performance in the CPU, GPU, and memory. It also means their SSD is cheaper to make (whether that savings is passed on remains to be seen), and they provide 1 TB vs 850 GB by default.

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DecoyOctopusX

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@zoofame: Digital Foundry did a tear-down of the Xbox Series X showing the actual board. It is most certainly not using the same I/O stack as PS5. The SoC while still being produced by AMD is using quite a different configuration. This can be seen just by looking a the board shown by Digital Foundry.

No Caption Provided

Now without seeing actual chip serial numbers, having a block diagram, or decapping the chips we can't know the full details of Microsoft's I/O but just by counting the lanes you can tell that it is a fully different I/O controller. There are not enough lanes to support the same type of controller. Here is a link to the full video:

Loading Video...

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Jesus_Phish

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@decoyoctopusx: Without being told the I/O Channel numbers of having access to the PCB layout, it's impossible to count them from the images.

You're sort of comparing difference images and resources together in an apples and oranges way.

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cikame

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I'm a layman, the way i see it there has to be a downside to having unique CPU architecture, maybe it's better for games but not so good on the front end or other background tasks, maybe multiplatform games won't make full use of it, maybe it's another Cell where most developers can't grasp enough of it to be worthwhile though i think they won't repeat that mistake.
If it's somehow just better overall i don't know why this style of CPU wouldn't already be available elsewhere, it seems like something render houses would be clamouring for.
Personally i'm a PC user, so i'm just hoping moves like this don't disrupt the way things have been during this generation, the "normal" makeup of the current consoles very clearly helped multiplatform releases.

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DecoyOctopusX

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@jesus_phish:This is true because boards are multi-layered, but based off the layout it still seems pretty obvious that it is not using the same I/O controller.

@cikame: This is where the real problem lies. Third-parties are going to want to build games to reach the largest audience so they may not take full advantage of Sony's I/O stack because Sony programming interface(API) will not work on anything else. Will publishers allocate the budget to optimize specifically for PS5 when they have Xbox, NSW, and PC to worry about. I don't see it being likely.

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ThePanzini

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#6  Edited By ThePanzini

It's extremely doubtful any third parties would use the much faster SSD in the PS5 beyond better LODs, draw distance and load times.

Whats interesting though is Sony could have easily done what MS did, but instead traded 18% weaker cpu/gpu to more than double their SSD speed, they must have games in development to use that much SSD speed otherwise why bother.

@decoyoctopusx: You can easily flip the question, how many developers will use the SX extra 2tf beyond slighty better res or ray tracing. If the PS5 ends up being cheaper will the extra cost even be worth it as the difference will be negligible to most, especially when the SX won't have any exclusive software for two years.

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Seikenfreak

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#7  Edited By Seikenfreak

Whatever happens, it'll certainly be fun to watch the discussion and discovery unfold over the coming year I think. Even if Sony first-party teams are the only ones to take advantage of the unique benefits, Sony absolutely destroyed with their first-party titles this gen and, IMO, are what let the system stand above the rest. A healthy portion of the systems game library are those exclusives in comparison to where Microsoft has been at with Halo, Gears, and Forza.. And yes, then everything around that topic is up for debate because Microsoft's PC presence and their new developer acquisitions etc etc.

That all being said, something I would really love an outlet like Digital Foundry to do would be to sit down with an experienced developer or team and have them talk about what these new hardware specs could change about how games are designed, but more broadly.

Does the PS5s ability to pull huge amounts of data just mean that open world games can be bigger? Or will they just be more densely packed with assets? How could it affect the racing game genre? Will Gran Turismo 7 be able to render a lot of cars on track or is that still an issue because it's more about the computational power to handle the AI and physics? Does it again just fall back to the race tracks being more detailed or can they finally put the Isle of Man course in the game that they scanned years ago but is far larger than even the Nurburgring Nordschleife? How can it change the shooter genre or RPGs? More assets and detailed environments just means more work for artists, and if games are already hugely expensive to produce, and now this allows for an order of magnitude more stuff.. Who even has the time or budget to build that?

That's the sort've talk I'd love to see people really dig into. How does this new hardware theoretically benefit games and game design, hopefully beyond just.. larger areas. I can understand how this will make titles like Grand Theft Auto or Horizon Zero Dawn 2 unbelievable and potentially unlike anything we've ever seen but what about everything else?

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infinity_thor

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Lot of damage control going around these days on these PS specs to rationalize the weaker console for two straight releases now (xbox one x vs ps4 pro and now this gen).

Xbox has also mentioned the Velocity architecture that has been largely ignored in these spec analyses.

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redspider

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Amazing

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MonkeyKing1969

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Eurogamer/Digital Foundry have another new video up. Sorry folks but it sure seems like they are saying, we just won't know until we see games where all the ports can be measured. It is not a cut & dry count of parts to parts that matters for output. We are going era where the parts that make up the whole are more closely integrated and have a much bigger impact on what shows up on screen.

I think more than ever, the price will matter A LOT. The human malware situation is going to make budgets 'at home' tight. I think even without thing being equal being less expensive will be a huge BOON for the company that can swing a lean price.

Newest 4/2/20 DF Video