Understanding the PS5's SSD: A deep dive into next-gen storage tech

The PlayStation 5's new SSD is revolutionary, delivering massive efficiency through speed and enabling true next-gen performance on the console.

@DeekeTweak

Published Mar 18, 2020 6:00 PM CDT
Updated Nov 3, 2020 11:44 AM CST

20 minutes & 3 seconds read time

The PlayStation 5's new solid state drive isn't your run of the mill PCIe 4.0 SSD. It's heavily customized on a number of levels, including its revamped 12-channel memory controller. While on the surface it has similar specs to a PC-level SSD like PCIe 4.0 interface with 4x lanes on an M.2 card using the NVMe protocol, it's been built from the ground up specifically for the system's custom 7nm AMD SoC and 16GB of GDDR6 system memory. And in many ways, the SSD is the most important part of the PlayStation 5.

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The SSD can deliver uncompressed data to other system components at up to 5.5GB/sec via its new proprietary hardware, which is over twice that of an Xbox Series X. And like the Xbox Series X, the PS5 also has dedicated hardware-based decompression to reduce CPU overhead. The new custom-designed I/O unit is the heart of making all this happen.

In this article we'll be combing through Mark Cerny's latest technical dissection of the PlayStation 5 hardware and putting everything into perspective along the way. This will be a long ride, but if you have even a passing interest in next-gen console storage, it'll be worth checking out.

Let's start with the five main tenants that shaped the PlayStation 5's SSD:

Boots in a second
No load screens
Ultra high-speed streaming
De-duplicate game data
No long patch installs

The PS5 architect starts by revealing a startling figure in just how clunky current HDDs are for game design and execution.

"My rule of thumb is that the hard drive is spending 2/3s of its time seeking, and only 1/3 actually loading data. 1GB is roughly 20 seconds to load from a hard drive."

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With the PlayStation 5's new custom PCIe 4.0 SSD, Sony can load 5GBs of data in a single second. That's 2GBs in 0.27 seconds. Loading screens are basically eliminated from this raw power.

"We're talking two orders of magnitude faster, meaning very roughly 100 times faster. Which means at 5GB/sec on the SSD that the game boots in a second. There are no load screens. The game just fades down and loads a half-dozen gigabytes, and fades up again. Same for a reload. You immediately get back into the game after you do. And fast-travel becomes so fast that in a blink of an eye you're present."

Loading a game from a hard drive is a different story altogether.

"As a player you wait for the game to boot, wait for the game to load, wait for the level to re-load every time you die, and you wait for what is euphemistically called fast travel."

One of the biggest aspects of the PS5's SSD power is efficiency through speed.

Cerny talks about how devs do creative things to obfuscate and distract gamers from the long load times.

The system's solid state drive significantly reduces the duplication found in today's biggest games. Modern games mitigate read speed limitations by by segregating pieces of a game into data chunks that use tons of duplicated assets and lead to big file sizes. Now with the 5GB/sec throughput for data processing, developers don't have to worry about replicating assets.

"The data can be duplicated so many times that it no longer fits on a Blu-ray disc. You end up with hard limits on the player's run speed or driving speed. The player can't go faster than the load speed on the hard drive."

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Cerny asserts this will not only change how games are played, but how they're made.

Developers will no longer have to design their games specifically around storage limitations. A lot of the level design in games have specific sequences to optimize data loading. An elevator segment lets the game prepare for the next transition. A winding cave does the same, separate key parts of the world and gives the system an opportunity to load the rest of the next environment.

The system's SSD speeds are so high devs can stream assets directly into the pipeline as they're needed. There's no seeks with an SSD.

"What if the SSD is so fast that as the player is turning around, it's possible to load textures? If it takes half a second to turn, that's 4GB of compressed data you can load."

The result is games that load in less than a second. The PS5's load times are so fast that devs may actually have to artifically slow them down so gamers don't get disoriented, Cerny says.

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RAM optimizations

Another major benefit is how system memory will be utilized, in particular its data cache.

The PlayStation 5 features 16GB of GDDR6 unified RAM with 448GB/sec memory bandwidth. This memory is synergized with the SSD on an architectural level and drastically boosts RAM efficiency. The memory is no longer "parking" data from an HDD; the SSD can deliver data right to the RAM almost instananeously.

Essentially the SSD significantly reduces latency between data delivery and memory itself. The result sees RAM only holding assets and data for the next 1 second of gameplay. The PS4's 8GB of GDDR5 memory held assets for the next 30 seconds of gameplay.

"There's no need to have loads of data parked in the system memory waiting to potentially be used. The other way of saying that is the most of the RAM is working on the game's behalf."

The SSD allows Sony to keep RAM capacity down and reduce costs.

"The presence of the SSD reduces the need for a massive inter-generational increase in size."

Cerny also confirms the PlayStation 5's SSD improves how patches are installed on the storage. The system no longer needs to create a new file every time a patch is installed. This was previously necessary because the patch would add new seeks, and thus compound the data usage even further.

But as we said above, there's no seeks on the SSD.

"This means no installs as you know them today."

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Custom tech

Speed isn't everything though. Sony had to design new software systems on an architectural level to complement the SSD's new capabilities. To get the most out of the new PCIe 4.0 storage, Sony had to reconfigure the base systems that communicate with game code.

"Our goal with the PS5 isn't just that the SSD would be 100x faster. It's that game loads and streaming would be 100x faster as well. So every single potential bottleneck needed to be addressed. And there are a lot of them."

Right now, CPU overhead from data decompression and management is pretty high. The more data that's moved, the more the CPU is taxed, and if it's pushed too far, frame rates drop astronomically. That's a big reason why Sony is optimizing data streaming on the system to ensure pipelines are flowing with enough speed and efficiency so that games look, feel, and run better than ever.

"To solve these issues, we built a lot of custom hardware, namely a custom flash controller and a number of custom units in our main chip."

The flash controller, why may have been designed by Samsung (along with the memory), has 12 channels and offers bandwidth of 5.5GB/second. Six of them are prioritized for gaming.

Cerny says the 12 channel interface was the main reason Sony chose the odd 825GB storage capacity for the PlayStation 5.

The architect strongly hints that PS5 game installs will be massively reduced, unlike the huge 100GB leviathans we have today. So 825GB on the SSD should stretch farther than 1TB on today's normal HDD.

"The question remains: Is this enough? It's tempting to add more, but flash certainly doesn't come cheap and we have a responsibility to our gaming audience to be cost effective with regards to what we put in the console."

To figure out if more storage was needed, Sony surveyed what kinds of games PS owners were playing and whether or not they'd fit on the SSD.

"We were able to establish the friction cost by re-installs and re-downloads would be quite low. And so we locked in on that 825GB size."

Four lanes of the custom 12 channel memory controller connect directly to the PCIe 4.0, meaning we're getting x4 performance (Anyone who's read up on PCIe 4.0 will have seen mention of x4 lanes and the improvement boosts this spec offers).

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Storage Expansion

But what about expandable storage? HDDs are still supported, but gamers need a way to expand the higher-end SSD performance to ensure they can keep playing PS5 games. Pretty much every game is getting bigger and bigger now, and even with compression techniques and massive efficiently toolsets, 825GB won't be enough indefinitely.

Sony solves this by allowing select PC M.2 SSDs to swap into the console. Sony won't roll out proprietary memory card storage for the PS5, unlike Microsoft.

Gamers can buy an appropriately-specced PC SSD off the shelves and plug it right into their PlayStation 5 to expand the memory. There's a few catches, though: The SSD needs to be at least as fast as the PS5's internal drive, and it needs to be approved by Sony first to ensure compatibility.

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Hardware-based compression

Compression is a huge part of the PlayStation 5's data management. The console will have a powerful new compression system that essentially shrinks data and reduces the overall install size of data on your SSD. So not only will games have less redundant assets, they can be smaller, too.

Like the Xbox Series X, the PlayStation 5 will have its own hardware-based compression block that's situated on the 7nm SoC.

Basically this means a section on the console's main chip will be dedicated to decompressing data. This will help the CPU in decompressing the compressed data from downloads, installs, and discs.

Decompression is very taxing on a CPU and causes lots of overhead, so this will free up the CPU to other in-game tasks like higher frame rates.

The PS5 uses a derivative of RAD Tool's potent Kraken decompression technology, which offers 10% better compression--that's about 10% more installations or data on a Blu-ray disc. Without the dedicated decompressor, it would take 9 Zen 2 CPU cores to decompress Kraken-level data.

The SoC also has a DMA (direct memory access) controller that allows devs to designate where data goes to the SSD. It's a means of further reducing data-streaming bottlenecks.

The I/O complex further houses two co-processors that help direct that data traffic. One co-processor is focused on SSD input-output that's specifically designed to bypass file read bottlenecks. The other handles memory mapping. The SRAM, or static RAM, which grants faster access to cached memory.

Finally there's a block dedicated to coherency engines which work directly with the GPU to optimize caching. The engines communicate with the GPU, which "scrubbers" that clean up cached data on the GPU itself to improve efficiency and ensure the cache isn't filled with redundant data.

Summary

There's still a lot we don't know about the PlayStation 5's SSD, like what time of flash memory it uses (likely QLC), who built it (likely Samsung), and all of the other architectural components that help tie the hardware together on a software level.

But Cerny's deep dive gives a great look at what to expect from the PlayStation 5's storage technology in the future...and just like the Xbox Series X, the PS5's SSD will transform console gaming as we know it. Developers will be armed to the teeth to defeat bottlenecks and create expansive, wide, and vastly immersive open worlds the likes of which we've never seen before.

Hopefully soon we'll actually see some PS5 gameplay and the system in action. But for now, I think Sony dished out quite a bit of info.

The console will release in Holiday 2020, and it may cost $499.

Check below for more info on everything we know about the PlayStation 5 so far:

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PlayStation 5 specs and details:

Custom SoC with second-gen Navi GPU, Zen 2 CPU
8-Core, 16-thread Zen 2 CPU at 3.5GHz
Navi GPU with 36 CUs on RDNA 2, 2.23GHz
Navi, Zen SoC uses new AMD RDNA 2.0 architecture
Ultra-fast 825GB SSD with up to 9GB/sec speeds
Support for 4K 120 Hz TVs
Ray-tracing enabled
8K output support (for gaming)
Plays PS4 games, BC is on a title-to-title basis
Separate games that ship on BD-XL Blu-ray discs
New controller with extensive haptic and tactile feedback

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