As you'll appreciate when you see the deep-dive presentation released today, there's a wealth of new information about Sony's next-generation console plans here, and that's before we go really in-depth with the information Mark Cerny shared with us beyond the content of today's presentation. With that in mind, we'll be presenting our content in two chunks. Today, we'll be looking at what we've learned from Sony's video broadcast, and a little further on down the road, we'll go deeper and share even more detail around the central pillars. In summary, however, these are the core details covered today:
- The technical specifications of PlayStation 5 and its innovative 'boost' approach to core clocks;
- The features of the PlayStation 5 GPU;
- How the SSD helps deliver the next-generation dream;
- How Sony tackles expandable storage;
- Unprecedented 3D audio fidelity via the Tempest 3D Audio Engine.
From the gamer's perspective, we know from our audience that there's an almost rabid hunger for the core technical specifications of the PlayStation 5 processor - and thanks to this presentation, we now know much more about the custom AMD processor at the heart of PlayStation 5. In truth, though, Cerny's focus in his presentation is more about the experience delivered by key features such as the SSD storage and the new Tempest audio engine - which is truly exciting stuff - but the anticipation level for the spec is such that this is where we'll start.
On a basic level, we already know that PlayStation 5 uses AMD's excellent Zen 2 CPU technology with prior communications confirming eight physical cores and 16 threads - but now we know how fast they are clocked, with PS5 delivering frequencies up to 3.5GHz. Discussing the nature of CPU and GPU clock speeds is going to require some careful explanation because Cerny actually described frequencies as being 'capped'. For the CPU, 3.5GHz is at the top end of the spectrum, and he also suggests that this is the typical speed - but under certain conditions, it can run slower.
|PlayStation 5||PlayStation 4|
|CPU||8x Zen 2 Cores at 3.5GHz with SMT (variable frequency)||8x Jaguar Cores at 1.6GHz|
|GPU||10.28 TFLOPs, 36 CUs at 2.23GHz (variable frequency)||1.84 TFLOPs, 18 CUs at 800MHz|
|GPU Architecture||Custom RDNA 2||Custom GCN|
|Memory/Interface||16GB GDDR6/256-bit||8GB GDDR5/256-bit|
|Internal Storage||Custom 825GB SSD||500GB HDD|
|IO Throughput||5.5GB/s (Raw), Typical 8-9GB/s (Compressed)||Approx 50-100MB/s (dependent on data location on HDD)|
|Expandable Storage||NVMe SSD Slot||Replaceable internal HDD|
|External Storage||USB HDD Support||USB HDD Support|
|Optical Drive||4K UHD Blu-ray Drive||Blu-ray Drive|
In fact, the transistor density of an RDNA 2 compute unit is 62 per cent higher than a PS4 CU, meaning that in terms of transistor count at least, PlayStation 5's array of 36 CUs is equivalent to 58 PlayStation 4 CUs. And remember, on top of that, those new CUs are running at well over twice the frequency.
Introducing boost for PlayStation 5
It's really important to clarify the PlayStation 5's use of variable frequencies. It's called 'boost' but it should not be compared with similarly named technologies found in smartphones, or even PC components like CPUs and GPUs. There, peak performance is tied directly to thermal headroom, so in higher temperature environments, gaming frame-rates can be lower - sometimes a lot lower. This is entirely at odds with expectations from a console, where we expect all machines to deliver the exact same performance. To be abundantly clear from the outset, PlayStation 5 is not boosting clocks in this way. According to Sony, all PS5 consoles process the same workloads with the same performance level in any environment, no matter what the ambient temperature may be.
So how does boost work in this case? Put simply, the PlayStation 5 is given a set power budget tied to the thermal limits of the cooling assembly. "It's a completely different paradigm," says Cerny. "Rather than running at constant frequency and letting the power vary based on the workload, we run at essentially constant power and let the frequency vary based on the workload."
An internal monitor analyses workloads on both CPU and GPU and adjusts frequencies to match. While it's true that every piece of silicon has slightly different temperature and power characteristics, the monitor bases its determinations on the behaviour of what Cerny calls a 'model SoC' (system on chip) - a standard reference point for every PlayStation 5 that will be produced.
The PlayStation 5 has variable frequencies for CPU and GPU, with an internal monitor adjusting clocks to keep the system within its power budget.
"Rather than look at the actual temperature of the silicon die, we look at the activities that the GPU and CPU are performing and set the frequencies on that basis - which makes everything deterministic and repeatable," Cerny explains in his presentation. "While we're at it, we also use AMD's SmartShift technology and send any unused power from the CPU to the GPU so it can squeeze out a few more pixels."
It's a fascinating idea - and entirely at odds with Microsoft's design decisions for Xbox Series X - and what this likely means is that developers will need to be mindful of potential power consumption spikes that could impact clocks and lower performance. However, for Sony this means that PlayStation 5 can hit GPU frequencies way, way higher than we expected. Those clocks are also significantly higher than anything seen from existing AMD parts in the PC space. It also means that, by extension, more can be extracted performance-wise from the 36 available RDNA 2 compute units.
Not wishing to draw comparisons with any existing hardware past, present or future, Cerny presents an intriguing hypothetical scenario - a 36 CU graphics core running at 1GHz up against a notional 48 CU part running at 750MHz. Both deliver 4.6TF of compute performance, but Cerny says that the gaming experience would not be the same.
"Performance is noticeably different, because 'teraflops' is defined as the computational capability of the vector ALU. That's just one part of the GPU, there are a lot of other units - and those other units all run faster when the GPU frequency is higher. At 33 per cent higher frequency, rasterisation goes 33 per cent faster, processing the command buffer goes that much faster, the L1 and L2 caches have that much higher bandwidth, and so on," Cerny explains in his presentation.
"About the only downside is that system memory is 33 per cent further away in terms of cycles, but the large number of benefits more than counterbalance that. As a friend of mine says, a rising tide lifts all boats," explains Cerny. "Also, it's easier to fully use 36 CUs in parallel than it is to fully use 48 CUs - when triangles are small, it's much harder to fill all those CUs with useful work."
Sony's pitch is essentially this: a smaller GPU can be a more nimble, more agile GPU, the inference being that PS5's graphics core should be able to deliver performance higher than you may expect from a TFLOPs number that doesn't accurately encompass the capabilities of all parts of the GPU. Developers work to the power limits of the SoC, their workloads affecting frequencies on the fly - but it's those factors that impact the clock speeds, not ambient temperatures.
Cerny acknowledges that thermal solutions on prior generation hardware may not have been optimal, but the concept of operating to a set power budget makes the concept of heat dissipation an easier task to handle, despite the impressive clocks coming from the CPU and GPU.
"In some ways, it becomes a simpler problem because there are no more unknowns," Cerny says in his presentation. "There's no need to guess what power consumption the worst case game might have. As for the details of the cooling solution, we're saving them for our teardown - I think you'll be quite happy with what the engineering team came up with."
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