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The PS5 will ship with "825 GB" of SSD space, which means we should see each of the 12 channels equipped with 64GiB of raw NAND, organized as either one 512Gbit (64GB) die or two 256Gbit (32GB) dies per channel. That means the nominal raw capacity of the NAND is 768GiB or about 824.6 (decimal) GB. The usable capacity after accounting for the requisite spare area reserved by the drive is probably going to be more in line with what would be branded as 750 GB by a drive manufacturer, so Sony's 825GB is overstating things by about 10% more than normal for the storage industry. It's something that may make a few lawyers salivate.

Most of the game design changes enabled by abandoning hard drives will have little impact on the gaming experience from one second to the next; removing workarounds for slow storage won't do much to help frames per second, but it will remove some other pain points in the overall console experience. For starters, solid state drives can tolerate a high degree of fragmentation with no noticeable performance impact, so game files don't need to be defragmented after updates.

Since game developers no longer need to care so much about maintaining spatial locality of data on disk, it will also no longer be necessary for data that's reused in several parts of a game to be duplicated on several parts of the disk. Commonly re-used sounds, textures and models will only need to be included once in a game's files. This will have at least a tiny effect on slowing the growth of game install sizes, but it probably won't actually reverse that trend except where a studio has been greatly abusing the copy and paste features in their level editors.

Warnings to not turn off the console while a game is saving first showed up when consoles moved away from cartridges with built-in solid state storage, and those warnings continue to be a hallmark of many console games and half-assed PC ports. The write speeds of SSDs are fast enough that saving a game takes much less time than reaching for a power switch, so ideally those warnings should be reduced, if not gone for good.

All of the RAM used by a game can be saved to a NVMe SSD in a matter of seconds, like the save state features common to console emulators

But those are all pretty much convenience features that do not make the core game experience itself any richer. The reduction or elimination of loading screens be a welcome improvement for many games—but many more games have already gone to great lengths to eliminate loading screens as much as possible.

SSD As RAM?

Finally, we come to what may be the most significant consequence of making SSDs standard and required for games, but is also the most overstated benefit

Whatever qualifiers and caveats those statement came with quickly get dropped by fans and even some press. So let's be clear here: the console SSDs are no substitute for RAM. The PS5's SSD can supply data at 5.5 GB/s. The RAM runs at 448 GB/s, *81 times faster*. The consoles have 16 GB of GDDR6 memory. If a game needs to use more than 16 GB to render a scene, framerates will drop down to Myst levels because the SSD is not fast enough. The SSDs are inadequate in both throughput and latency.

This difference means an SSD-based console (especially with NVMe performance) can free up some VRAM and allow for some higher-resolution assets. It's not a huge change; it's not like the SSD increases effective VRAM size by tens of GBs, but it is very plausible that it allows games to use an extra few GB of RAM for on-screen content rather than prefetching off-screen assets.

Microsoft has stated that these capabilities add up to the effect of a 2x or 3x multiplier of RAM capacity and SSD bandwidth. I'm not convinced. Sure, a lot of SSD bandwidth can be saved over short timescales by incrementally loading a scene. But I doubt these features will allow the Series X with its ~10GB of VRAM to handle the kind of detailed scenery you could draw on a PC GPU with 24GB of VRAM.

Sony has outlined their plan for dealing with this challenge: their SSD implements a custom feature to support 6 priority levels for IO commands, allowing large amounts of data to be loaded without getting in the way when a more urgent read request crops up

Excess latency happens when you give the SSD more requests than it can work on simultaneously; some of the requests have to sit in the command queue(s) waiting their turn. If there are a lot of commands queued up, a new command added at the back of the line will have a long time to wait. If a game sends the PS5 SSD new requests at a rate totaling more than 5.5GB/s, a backlog will build up and latency will keep growing until the game stops requesting data more quickly than the SSD can deliver. When the game is requesting data at much less than 5.5GB/s, every time a new read command is sent to the SSD, it will start processing that request almost immediately.

So what's most important is limiting the amount of requests that can pile up in the SSD's queues, and once that problem is solved, there's not much need for further prioritization. It should only take one queue to put all the background, latency-insensitive IO commands into to be throttled, and then everything else can be handled with low latency.

Storage Matters: Why Xbox and Playstation SSDs Usher In A New Era of Gaming

www.anandtech.com