What’s the Xbox Series X Mystery Port? It’s for Expandable Storage

Posted on February 4, 2020 by Brad Sams in Xbox Series X, Xbox with 20 Comments

As we move towards the next generation of consoles, one item that is presenting challenges for Microsoft (and likely Sony too) is that games are getting bigger. If you look at titles like the most recent Call of Duty, they can easily surpass 100 GB in size.

With next-generation consoles pushing for 4k graphics with additional visual enhancements, the size of a game is only going to increase which means that storage is becoming a challenge. Even though 1TB is sufficient for most PCs these days as documents and other content is much smaller, for a console, that could mean only having 9 or fewer games installed on your device.

A few weeks back, we got our first look at the backside of the Xbox series X. At that time, I believed the long-rectangular port between the HDMI and digital audio port that was for diagnostics and I was incorrect. That port is for storage expansion, according to people familiar with the company’s plans, and offers the series X a work-around as games continue to expand in size.

The bigger question, which I don’t know the answer to quite yet, is what technology is Microsoft using for the expandable storage. Considering that the internal drive is going to be of the ‘high-performance’ variety, a flavor of NVMe is expected and not a platter drive, external storage needs to be quick as well. While the back of the device does have USB ports that could be used for expansion, that mystery slot is a dedicated storage expansion for high-speed hardware.

A couple of weeks back, a reader actually dug up some interesting information that could identify the exact components inside the console. The thereverendslim wrote in our forums:

Given that 1) the “debug port” on the Xbox Series X looks to be roughly 31mm x 4mm, 2) that a LinkedIn entry showed Phison’s PS5019-E19T controller being developed for or used by the Series X, 3) that Phison’s datasheet for that controller shows that it can be used in a CFExpress form factor, and that the dimensions of a Type B CFExpress card are 29.8mm x 3.8 mm… Do you think it’s possible that rather than having an internal non-replaceable NVMe-style SSD, they are using Compact Flash Express for the SSD so that you can expand in the future?

And I think he/she may be right, but keep in mind that CFExpress cards are not cheap with a 512GB cards currently being sold for around $600. At that price, Microsoft is betting that the technology will drop significantly in price over the lifespan of the console or they have found a way to utilize that style of port with different storage.

The last option is that Microsoft does use CFExpress cards and lets the customer decide if they want to really spend the same price as the console on expanding the storage but that seems unlikely. Regardless of the outcome, Microsoft is looking at ways to expand storage options for its next-generation console with high-speed options that USB does not currently offer.

What this all means is that the Xbox series X will offer flexibility in your storage options and that if needed, it should be easy to expand the storage with a high-speed solution. Keep in mind, the console is still in development and Microsoft could make changes that remove this port but for now, it looks like the company is moving ahead with this type of functionality.

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Comments (20)

20 responses to “What’s the Xbox Series X Mystery Port? It’s for Expandable Storage”

  1. yoshi

    Sounds like the same thing Sony is doing(if rumors end up being true). The new generation is all going to come down to games and price. Hardware seems like it will be pretty much the same.

  2. hazeworth

    Who cares. Where's the dang console and the price . How bout a list of games . Features. Xbox 1 game compatible ?. If not they can keep all of it. Got too much already invested in Xbox 1. Microsoft. Her I wonder what PlayStation is doing rite now?

  3. Thretosix

    Don't care how much storage or expandable storage it has. The lack of an "HDMI in" on an Xbox One is blasphemous. Won't get a penny from me without one.

  4. Rycott

    I was reading an article that games may actually get smaller now that both consoles have confirmed SSD drives. To speed up load times on the old spindle discs some files were replicated upto nearly 20 times in a games install so they could be loaded faster as it spread some of these files around the platters.

    Whether this makes a huge difference in size is another matter as it depends on what files they were replicating. I imagine it probably wasn't textures which would be some of the biggest parts.

  5. nuclearpalsy

    The port is for the Kinect 2.0.

  6. ngc224

    In reply to MikeGalos:

    …or Microsoft is trying to extend the news cycle for the “leaked” Xbox Series X ports?


  7. hazeworth

    Plus they need to expand the selection of multiplayer games. And multiplayer games online. Instead of 1 player per console. Stop being greedy think about families that all enjoy gaming . If I got 2 kids they shouldn't need 2 consoles to play together. But most games especially the good ones require 2 systems. Smh. Instead of upgrading what we already have why not try something different. It's not a real entertainment for family to enjoy together.

    • orbsitron

      In reply to hazeworth: 
      Halo Infinite will support split-screen. Forza is a rumored launch title and traditionally has split screen support. Hopefully next gen results in embracing couch co-op and split screen gaming more than the XBOX One / PS4 generation did.

    • thereverendslim

      In reply to hazeworth:

      The lack of splitscreen gaming is less about the hardware than it is developer investment. Splitscreen gaming has become such a niche thing that most developers don't want to expend the resources anymore. Doing more than one viewport and additional input means they have to re-optimize and test that functionality, which adds cost to the project.

  8. waethorn

    CF Express Type-B is limited to PCIe 3.0 x2.

  9. thereverendslim

    In reply to MikeGalos:

    Is that a limitation of the form factor itself or controller chip used? In other words, if it physically supports 4 lanes and you have a Gen4 controller like the one on the Phison spec page (which I can't link to here, apparently), could the Type-B 2.0 enclosure handle PCIe 4.0 x4?

    This is the page I'm referring to (if you swap the dots):


    • hoodyracoon

      In reply to thereverendslim:

      Honestly it could be anything, probably storage, but even if it's storage it could just as easily be a 3042 m.2 in a incloser instead of a cfe, or they could have licensed the cfe encloser spec and are just sticking 3rd part nvme ssds in it, who knows,

      If it's pcie it could be anything with that size, it slightly larger then all m.2 forms, and honestly anything but the 2.5in ssd formfactors would fit in the hole, so long as they don't lock it to 1st party nvme drives adapters will come out quickly anyways, and undoubt that Microsoft will drop USB HDD support,but here's for hoping they add in USB 4.0 to the console so that will the a option for expansion

      • thereverendslim

        In reply to hoodyracoon:

        My speculation about it being CFExpress was based on a LinkedIn entry for a guy who helped make that particular Phison controller and said it was for the Series X and that it was a DRAM-less controller. When you look that controller up on Phison's website, it supports either NVMe or CFX... so it could really go either way. The reason I leaned toward CFX was that a rough sizing check of that slot (based on the known size of the ethernet and HDMI ports) seems awfully similar to CFExpress Type B slots in existing photography gear. Of course, I could be totally off-base and it could be some bizarre new port they made for debugging... but that would seem unnecessary, considering.

        As far as USB HDD support... I don't know that they would need to drop it. Since they're using AMD, AMD's StoreMI tech would let them do some intelligent buffering in and out of SSD/RAM to make an external HDD viable for storage.

  10. thereverendslim

    I'm a he. And there's no cost/material reason for CFExpress cards being so high in price... They're just not widely manufactured because they're only used in niche products like high-end cameras. The tech in the enclosure itself is not vastly different than what you see on a NVMe stick. So it wouldn't surprise me at all if Microsoft can get these at a price similar to what we see equivalent NVMe sticks run. It's basically a hot-swappable cartridge version of the tech.

    You can see that this controller supports CFX on Phison's page though there is curiously no data sheet for that controller as of yet. Makes you wonder if the reasoning behind a Gen4 controller with Gen3 sustained speeds at this level is because of the inherent cooling issues with the CFExpress form factor (i.e. you can't slap a heatsink on it like my Gen4 NVMe has in my PC). I'm betting this is a purpose-built Gen4 controller for this format so you can get the burst/random ops speeds of Gen4 but limit the Gen3 speeds for sustained read/writes so that you don't overheat the CFX board/enclosure.

  11. madthinus

    Nice find!

  12. ngc224

    I wonder why a leaked image of a prototype would not have a label for the mystery port like the other ports?

  13. remc86007

    Storage is my primary concern with the new console. I have 6TB of games on my XB1X and that's not anywhere close to all my games. If new games are designed in a way that necessitates faster than HDD speeds, and they can't fall back on page file in NVME, there is going to be problems.

    I could definitely keep fewer games stored locally if Comcast would get rid of or dramatically raise my 1TB data cap, but as it stands, I usually only have 100GB of data left at the end of the month.

    • IanYates82

      In reply to remc86007:

      It's odd to me (but good for me) that as Australian ISPs started offering decent unlimited bandwidth plans, many in the states started getting caps.

      I was so envious for years due to my 300GB cap that'd be ruined by some game updates, etc each month back when I got my original xbox one. Now that I have unlimited I'd *hate* to be forced back.

    • reformedctrlz

      In reply to remc86007:

      Lucky you, my only internet option is a local company and my cap is 500gb. The option for unlimited is an additional fee