Can someone explain to me why the Series X SSD is PCIe 4.0?

Deleted member 16908 · Oct 21, 2020

At 2.4 GB/s, the Series X SSD doesn't even max out the 3.5 GB/s potential of PCIe 3.0. So why did they choose to use 4.0? Couldn't they have saved money by going with 3 instead of 4?

I know it does 4.8 GB/s compressed but isn't that still just 2.4 GB/s that turns into 4.8 once it's decompressed?

Caiusto · Oct 21, 2020

They said they wanted the speed at all times, no drops. I think that has something to do with it

rare · Oct 21, 2020

I wouldn't be surprised if it's because 4.0 just A. Too cost intensive and B. Time constraints to get the console out on time

alphacat · Oct 21, 2020

Futureproofing maybe with new SSD's in revisions?

Kuro · Oct 21, 2020

The newer standard will probably be cheaper in the long run is usually the answer. Futureproofing ties into that.

Praedyth · Oct 21, 2020

They get to use less lanes, I guess?

BlastProcessing · Oct 21, 2020

There is more to an SSD than just raw read speeds.

DieH@rd · Oct 21, 2020

In PCs M.2 port for storage uses four PCIE gen4 lanes with the onboard controller being the bottleneck [at first it was ~4GB/s, newer ones this holiday season will go to 7.5GB/s].

SeriesX uses two lanes.

edit-expanded

Belthazar90 · Oct 21, 2020

DieH@rd said:
In PCs M.2 port for storage uses four PCIE gen4 lanes, SeriesX uses two lanes.

His question was why not use gen3 with more lanes to achieve the same speed with less cost.

DieH@rd · Oct 21, 2020

Belthazar90 said:
His question was why not use gen3 with more lanes to achieve the same speed with less cost.

Less lanes = cheaper motherboard & cheaper drive.

Same as with DDR3 in Xbox One, they long time ago decided that sub 3 GB/s + HW decompression will be enough for them.

gofreak · Oct 21, 2020

Belthazar90 said:
His question was why not use gen3 with more lanes to achieve the same speed with less cost.

Would 3 (or 4, if you have to go in 2s) lanes of pci3 be cheaper than 2 of pci4? Would it not maybe have knock on effects for traces, mobo complexity?

LordBlodgett · Oct 21, 2020

I'm just guessing futureproofing. I still think there will be a mid gen upgrade to these consoles depending on how tech moves forward over the next 5 years....

cyrribrae · Oct 21, 2020

Disclaimer: I am not smart or knowledgeable about anything. (I should start including this on every post I make :p)

Yea, it's about using less lanes. So they're using the higher throughput per lane that 4.0, but using fewer lanes to get there. Saves on what you need to do with the rest of the stuff. It should actually be cheaper overall this way.

I think.

show me your skeleton · Oct 21, 2020

will be updated with a day 3 patch (when the ps5 is released) and then itll be 9tb/s through gamepass

Calibro · Oct 21, 2020

Because there's no cost to save there if you're using Zen 3 AMD architecture already.

EvilBoris · Oct 21, 2020

Because speed isn't the only feature.

PCIE 4.0 also has new NVMe protocols as part of the spec, it also supports DRAM-less solutions like used in the Xbox Series X, these are more power efficient and cooler.

Digital Savior · Oct 21, 2020

You get to use half as many PCIe lanes when using gen 4 over gen 3. Everything has a cost. Especially when scaled to millions of units.

Night Hunter · Oct 21, 2020

Cost savings in the long run I guess.

Unfortunately not for the consumer though.

Tomte Arme · Oct 21, 2020

i belive they use 4 pci4 lanes 2 for onboard 2 for expansion instead of 8 pci3 lanes

Vash63 · Oct 21, 2020

4.0 is a built in feature with AMD's modern SoCs, so this lets them save money by using fewer lanes (fewer physical traces, pins and contacts needed everywhere).

Windu · Oct 21, 2020

They are using this hardware in the datacenters as well, may be related to that.

Parker Petrov · Oct 21, 2020

Robinson said:
At 2.4 GB/s, the Series X SSD doesn't even max out the 3.5 GB/s potential of PCIe 3.0. So why did they choose to use 4.0? Couldn't they have saved money by going with 3 instead of 4?

I know it does 4.8 GB/s compressed but isn't that still just 2.4 GB/s that turns into 4.8 once it's decompressed?

According to Microsoft they wanted a sustained read and write and focused on that. Where PlayStation operates more like a standard drive where the number they have is peak performance but wouldn't beable to sustain a write that speed for a extended period of time. Neither method is wrong. its just a different way to do things. It will be interesting to see as the generation how two the paths shakeout and if the in the end it even matters. Both consoles will have blistering face loads compared to what we have now.

ShapeGSX · Oct 21, 2020

Robinson said:
At 2.4 GB/s, the Series X SSD doesn't even max out the 3.5 GB/s potential of PCIe 3.0. So why did they choose to use 4.0? Couldn't they have saved money by going with 3 instead of 4?

I know it does 4.8 GB/s compressed but isn't that still just 2.4 GB/s that turns into 4.8 once it's decompressed?

Because it is only using 2 lanes of PCIe 4.0. PCIe 4.0 has twice the bandwidth of PCIe 3.0.

Removing PCIe lanes on the APU saved them chip area and saved them build cost. They saved 2 PCIe lanes for the internal and 2 PCIe lanes for the external. It saves in board area, as well. And it likely saved them area for their CF Express expansion cards, as well.

Also, it is guaranteed to have 2.4GB/s minimum. It can go faster.

dgrdsv · Oct 21, 2020

Robinson said:
So why did they choose to use 4.0?

Because Zen2 has a PCIE 4.0 controller built into it.

Jonnax · Oct 21, 2020

Because Zen 2 is natively PCIe 4.0

mordecaii83 · Oct 21, 2020

Zen 2 already supports PCIe 4.0, and using just 2 lanes of that would definitely be cheaper than 4 lanes of 3.0.

Edit: I didn't refresh and now I see it's been answered multiple times like 25 minutes ago lol...

ShapeGSX said:
Also, it is guaranteed to have 2.4GB/s minimum. It can go faster.

Just wanted to clarify on this, the max raw read speed is 2.4GB/s AFAIK, so it actually doesn't go faster. The numbers for compressed don't affect the physical transfer speed.

ShapeGSX · Oct 21, 2020

mordecaii83 said:
Just wanted to clarify on this, the max raw read speed is 2.4GB/s AFAIK, so it actually doesn't go faster. The numbers for compressed don't affect the physical transfer speed.

Good point. I did not state that the same way that Microsoft has. They state 2.4GB/s sustained.

Xbox Velocity Architecture: A Closer Look at the Next-Gen Tech Driving Gaming Innovation Forward on Xbox Series X - Xbox Wire

When we set out to design the Xbox Series X, we aspired to build our most powerful console ever powered by next generation innovation and delivering consistent, sustained performance never before seen in a console with no compromises. To achieve this goal, we knew we needed to analyze each...

news.xbox.com

Custom NVME SSD: The foundation of the Xbox Velocity Architecture is our custom, 1TB NVME SSD, delivering 2.4 GB/s of raw I/O throughput, more than 40x the throughput of Xbox One. Traditional SSDs used in PCs often reduce performance as thermals increase or while performing drive maintenance. The custom NVME SSD in Xbox Series X is designed for consistent, sustained performance as opposed to peak performance. Developers have a guaranteed level of I/O performance at all times and they can reliably design and optimize their games removing the barriers and constraints they have to work around today. This same level of consistent, sustained performance also applies to the Seagate Expandable Storage Card ensuring you have the exact same gameplay experience regardless of where the game resides.

behOemoth · Oct 21, 2020

Parker Petrov said:
According to Microsoft they wanted a sustained read and write and focused on that. Where PlayStation operates more like a standard drive where the number they have is peak performance but wouldn't beable to sustain a write that speed for a extended period of time. Neither method is wrong. its just a different way to do things. It will be interesting to see as the generation how two the paths shakeout and if the in the end it even matters. Both consoles will have blistering face loads compared to what we have now.

The PS5 uses 12 channels and TLC NANDs. The PS5 is way more capable to sustain the bandwidth.

However, the Xbox will use two channels to simply save costs.

mordecaii83 · Oct 21, 2020

ShapeGSX said:
Good point. I did not state that the same way that Microsoft has. They state 2.4GB/s sustained.

Xbox Velocity Architecture: A Closer Look at the Next-Gen Tech Driving Gaming Innovation Forward on Xbox Series X - Xbox Wire

When we set out to design the Xbox Series X, we aspired to build our most powerful console ever powered by next generation innovation and delivering consistent, sustained performance never before seen in a console with no compromises. To achieve this goal, we knew we needed to analyze each...

news.xbox.com

Yeah it'll definitely be fast enough for anything they want to do with it I'm sure.

M.Bluth · Oct 21, 2020

Parker Petrov said:
PlayStation operates more like a standard drive where the number they have is peak performance but wouldn't beable to sustain a write that speed for a extended period of time.

There is no evidence to support this assertion.
For all intents and purposes both the 2.4GB/s figure from Xbox and 5.5GB/s from Playstation are sustained, guaranteed read performance.

Flash · Oct 21, 2020

Future proofing.

The next "slim" Xbox Series X, in 4 years, will have an upgraded SSD with improved speeds.

Chief Malik · Oct 21, 2020

dgrdsv said:
Because Zen2 has a PCIE 4.0 controller built into it.

nextJin · Oct 21, 2020

Calibro said:
Because there's no cost to save there if you're using Zen 3 AMD architecture already.

This is basically the answer. It's already built into the architecture. They just chose to use fewer lanes. They could have added it but chose not too.

JeffGubb · Oct 21, 2020

I bet that a part of it is just the velocity architecture (that enables the SSD to hook directly into the GPU) works best over PCIe 4.0.

Timlot · Oct 21, 2020

M.Bluth said:
There is no evidence to support this assertion.
For all intents and purposes both the 2.4GB/s figure from Xbox and 5.5GB/s from Playstation are sustained, guaranteed read performance.

I do find it interesting that Xbox goes out of their way to emphasize their SSD speed for both the internal and external SSD is sustained. Not to say the PS5's internal SSD speed isn't sustained, but because it can except standard PC nvme SSD those could certainly have inconsistent performance.

Can someone explain to me why the Series X SSD is PCIe 4.0?

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