There’s absolutely no way I can recommend a Thunderbolt eGPU setup with the ASUS Flow
Z13.
I’ve had 3 major problems with it, this is what you need to know!
This ROG Flow Z13 gaming tablet has Nvidia’s RTX 3050 Ti inside, but it’s also got the
most potential GPU expansion out of any device so far.
Not only does the Z13 have Thunderbolt 4 support, so we can attach a desktop graphics card over
Thunderbolt, but ASUS also offers their XG Mobile.
Basically any laptop with a Type-C thunderbolt 4 port can use the desktop GPU enclosure,
while ASUS’s XG Mobile currently only works with their devices that have this custom port.
Right now this includes their Z13, X13 and X16.
Now a Thunderbolt external graphics enclosure like this one obviously gives you more upgradeability
because you can install whatever desktop card you like.
I’ve got Nvidia’s original RTX 3080 in this one.
The XG Mobile I’ve got uses a laptop RTX 3080 GPU, so it’s less powerful compared
to the desktop 3080 in terms of the raw specs.
The mobile GPU in the XG Mobile has less CUDA cores and a lower power limit compared to
the desktop version, but it’s also much smaller and more portable as a result, though
at the expense of less upgradeability as you’d have to replace the whole XG Mobile unit if
you want to change the GPU.
Interestingly the XG Mobile 3080 has more VRAM than the desktop card, however the desktop
card is using faster GDDR6X memory.
One of the biggest downsides of a Thunderbolt eGPU setup is that it's limited to 4 lanes
of PCIe Gen 3 over Thunderbolt, and depending on the device you’re connecting it to, that
signal might first need to go via a Thunderbolt controller that’s external to the processor.
Modern Intel architectures have that built in to the CPU though, which does give a performance
improvement.
But still, this is the main reason why a desktop graphics card performs worse in a Thunderbolt
eGPU enclosure compared to just running it in a desktop PC.
There’s just more overhead with Thunderbolt.
The XG Mobile on the other hand uses 8 lanes of PCIe Gen 3, it’s simply a more direct
connection with more bandwidth.
Alright now here are the 3 major problems that I had while testing a Thunderbolt eGPU
with the Z13.
The first major problem was any time I connected my Mantiz Saturn Pro II eGPU enclosure over
here, the Z13 would blue screen within about a minute.
Then it would just sit there in a boot loop until I unplugged the enclosure.
Now I was able to work around this by using DDU to uninstall the Nvidia drivers then connect
the enclosure and then reinstall the Nvidia drivers, but that’s not exactly something
practical you’d want to do every time you connect your eGPU to Z13.
Now fortunately ASUS were able to replicate this a couple of months ago or so and they
have since rolled out an update that fixes the problem through the MyASUS software.
So as far as I’m aware, that issue is fixed.
But the second issue I had was equally annoying.
When we connect an external GPU via Thunderbolt to the Z13, the Windows operating system sees
it as a hardware change.
It’s got a new GPU.
Now with Windows 11, which is installed on the Z13 by default, Microsoft heavily encourages
if not forces you to use an online Microsoft account, and when it does this it enables
Bitlocker encryption by default for your security.
There’s just one small problem though.
Whenever Bitlocker sees that hardware has been changed, it freaks out and doesn’t
let you boot the machine.
So basically after I had that blue screen boot loop issue before, I was presented with
a Bitlocker screen.
This means I had to use a separate device with Internet access to log in to the Microsoft
account to retrieve the 48-digit Bitlocker key.
What a seamless process!
Don’t have a separate device with Internet connectivity?
Then I guess you’re not booting up the Z13.
My original workaround for this was to disable Bitlocker, but again ASUS have said that they’ve
fixed this problem in an update.
Connecting a new device via Thunderbolt shouldn’t register as a hardware change that triggers
Bitlocker.
Ok so that’s great, but I’m really starting to feel like I’m the BETA tester for this
product.
Especially when the third issue still exists in mid-May 2022.
The Z13 is charged with 100 watts over Type-C, and it comes with an ASUS branded 100 watt
Type-C charger.
Now my eGPU enclosure can offer 100 watts of Type-C charging over this single Thunderbolt
cable, so I should be able to plug this one cable in and fully power the Z13 right?
Wrong.
Apparently the Z13 can only get the full 100 watt charge with that included ASUS Type-C
charger.
I’ve been told that the reason for this is that the power gets sent directly to the
motherboard, which is meant to be more efficient.
Others apparently send the power first via the battery which acts as a bit of a buffer.
So with this design, if a third party charger has any sort of spike in power delivery, it
could potentially damage the device.
So to prevent a third party charger possibly killing the Z13, it is limited to 65 watts
with third party chargers, which includes the Thunderbolt enclosure.
So then the question becomes, is 65 watts of power delivery enough to give you full
performance with the Z13?
The answer seems to be probably not.
If I just run a CPU workload like Cinebench on loop, CPU package power seems to limit
to a 30 watt TDP in manual mode, while turbo mode is completely grayed out, which happens
when the charger isn’t connected.
If I instead connect the 100 watt ASUS charger to the bottom Type-C port and leave the eGPU
connected to the Thunderbolt port above, the CPU package power runs higher at 50 watts.
Which is also the same limit if we don’t have the eGPU connected.
So basically to get the full power limit with a Thunderbolt enclosure connected to the Thunderbolt
port, we also need to connect the ASUS power adapter to the bottom Type-C port at the same
time.
But Jarrod Technologies, maybe your eGPU just sucks?
ASUS thought that was a possibility too, and they said that the Z13 worked fine on two
separate enclosures based on their testing.
I did actually reach out to the Mantiz guys who make this GPU enclosure to see what they
think, and as far as they were aware they couldn’t understand why it would be a problem
with their enclosure.
I spent more than a month waiting for ASUS to provide me with one of their eGPU enclosures
that they tested on the Z13 to confirm it for myself, but it just didn’t end up happening
for whatever reason.
Eventually I reached out to Razer and asked if I could borrow the Core X Chroma, as it’s
basically a top of the line Thunderbolt eGPU enclosure and a bit more of a name brand compared
to the Mantiz enclosure.
Sorry buddy…
Anyway the exact same thing happens with the Razer enclosure.
The CPU TDP gets limited to 30 watts with only the eGPU connected and the ASUS 100 watt
charger needs to be connected at the same time for it to run up to 50 watts.
Ok, so just run the Z13 with two Type-C cables connected, problem solved right?
Unfortunately not.
Although connecting both Type-C cables does improve CPU only performance, game performance
was still all over the place.
Let’s see how 12 different games perform at 1080p, 1440p and 4K resolutions.
All game testing was done with Razer’s Core X Chroma with both Type-C cables connected
to the Z13 unless otherwise specified.
Let’s start out with Control, yeah it’s an older game now, but it’s one of the only
games out of the 12 where things actually look normal and how I’d expect, so it’s
a good place to start.
I’ve tested using the Z13’s screen at 1080p, and then with an external screen connected
directly to the eGPU, which should perform a little better because the signal doesn’t
need to get sent back from the eGPU to the Z13 and processed by the Z13’s GPU.
Anyway at the lower 1080p resolution, the higher bandwidth from the XG Mobile gives
us higher frame rates.
At 1440p and 4K though, the Thunderbolt eGPU setup is able to reach higher average FPS,
and this is because the desktop 3080 GPU is more powerful and it can get to work.
That said, the dips in performance shown by the 1% lows are extremely low with the Thunderbolt
setup, possibly due to the lower bandwidth, or maybe the CPU power limit shenanigans.
Alright now here’s Red Dead Redemption 2, and excuse me, but what the heck is going
on here?
There’s clearly some sort of bottleneck from the Thunderbolt eGPU setup, because it’s
only reaching a little over 30 FPS regardless of the resolution tested.
I tested this game on both the Mantiz Saturn Pro II and Razer Core X Chroma enclosures
and got the same results, so this is not a problem with a specific Thunderbolt enclosure.
For some reason the desktop graphics card just isn’t running properly, it’s running
at like 50% utilization with low power levels, but I can’t work out why.
I get the same results whether I run the test with one or both Type-C cables connected.
I also tried a fresh Windows reset, but this didn’t change anything either.
Just for comparison, last year the X13 with the same desktop GPU was reaching 61 FPS in
this test at 4K, so yeah, there’s an unknown problem here.
Watch Dogs Legion was running like garbage on the Thunderbolt eGPU too.
I mean, yeah sure if we lowered the settings down a bit or used DLSS it would perform a
bit better, but come on, the XG Mobile has a massive lead at all resolutions.
Even the 1% lows from the XG Mobile were far ahead of the average FPS coming out of the
Thunderbolt setup at 1080p and 1440p, an embarrassing result for Thunderbolt.
The numbers coming out of Shadow of the Tomb Raider on the other hand look good.
The desktop GPU is able to take the lead at higher resolutions as expected, but this game
demonstrates yet another problem I had with the Thunderbolt enclosure.
It wasn’t even able to load the game up on the Z13’s screen, it just kept crashing,
and that’s why there’s no data for it.
Granted I think most people would probably use an external screen on a Thunderbolt setup,
but regardless, not a good look.
The XG Mobile is far more portable so it’s a better option if you’re taking it with
you to boost gaming performance on the go with the Z13’s screen.
The Witcher 3 is another older game, but is another where the game crashed straight away
when loading it up on the Thunderbolt setup on the Z13’s screen, so at least 2 different
games that are unplayable unless you’re using an external monitor.
Cyberpunk 2077 looks alright in terms of average FPS, but the 1% lows coming out of the Thunderbolt
setup are beyond a joke.
The dips in performance and stuttering were more obvious compared to the XG Mobile, despite
it having a lower powered laptop GPU.
Sure the desktop GPU was giving a higher average FPS at 1440p and 4K resolutions again, but
it just wouldn’t be a great experience with those dips.
Especially considering how much money a setup like this would cost
This wasn’t the case for all games though, some like Dying Light 2 seemed to be fine.
The 1% lows weren’t a problem here.
The Thunderbolt setup was ahead in all regards at the higher 1440p and 4K resolutions, which
is what I expected from all games going into the testing.
Assassin’s Creed Valhalla was almost always doing better on the XG Mobile.
The Thunderbolt setup was only a couple of FPS ahead at the highest 4K resolution, and
it was only ahead for the average frame rate.
The dips in performance, measured by the 1% lows, were lower on the Thunderbolt setup,
meaning the XG Mobile is more consistent with less stuttering.
Metro Exodus was strange.
The XG Mobile setup lowered quite a bit at 1080p when connecting an external screen.
I’d love to retest it and confirm, but unfortunately ASUS needed it back a few weeks ago so I wasn’t
able to double check.
Due to this suspicious result, the Thunderbolt enclosure was ahead at 1080p for one of the
few times.
Microsoft Flight Simulator was generally behind on the Thunderbolt setup, unless you’re
doing 4K gaming where it was reaching a 24% higher average frame rate, but otherwise at
1080p and 1440p, the XG Mobile was doing better.
God of War was reaching basically the same average FPS at 1440p, but check out the differences
in 1% lows, the XG Mobile is simply offering a more stable experience.
Like many other games, the Thunderbolt setup was able to come out on top at 4K.
Forza Horizon 5 on the other hand was better on the XG Mobile at all resolutions, and the
dips in the 1% lows from the Thunderbolt setup were pretty bad compared to what the XG Mobile
is offering.
On average over all 12 games tested, at the lower 1080p resolution the XG Mobile was reaching
a 42% higher average frame rate.
Only one game, Metro Exodus Enhanced, was giving higher average FPS with the Thunderbolt
setup, but as mentioned I wasn’t able to retest that one.
The XG Mobile winning at 1080p was my expectation going in, because the higher bandwidth available
to the XG Mobile matters more at lower resolutions.
That said, some of the crazy results like Red Dead Redemption 2 and Watch Dogs Legion
definitely weren’t expected, something is wrong with the Thunderbolt setup there.
Stepping up to the higher 1440p resolution and the XG Mobile was now 24% faster compared
to the Thunderbolt plus desktop graphics card setup.
We can see this number is primarily being held up by the top 2 or 3 games though.
Then at the higher 4K resolution the Thunderbolt enclosure was finally able to offer an improvement.
The XG Mobile was now almost 8% slower in terms of average FPS out of the 12 games tested.
This doesn’t include 1% lows though because many games tested didn’t measure that, so
it’s harder to directly compare, but as we saw those could often be far worse with
the Thunderbolt setup.
GPU heavy tasks outside of gaming are less of an issue though, take 3DMark for example.
The more powerful desktop graphics card in the Thunderbolt enclosure was ahead regardless
of the test being run.
In a GPU heavy stress test, the Thunderbolt system was able to use substantially more
power, and that’s why these GPU heavy tasks are able to perform better with the desktop
card.
It’s just that for whatever reason, whether that be PCIe bandwidth limits, power delivery
issues to the CPU, or some other problem that the XG Mobile often does better in actual
games.
This wasn’t always the case though, especially in content creator workloads.
SPECviewperf was generally faster on the desktop GPU, but as we can see this wasn’t always
the case.
Blender was faster on the desktop GPU in the Monster and Junkshop tests, but the Classroom
test was doing better with the XG Mobile.
Maybe it can benefit more from the higher VRAM capacity, I’m just speculating, I don’t
know enough about these specific workloads to say.
DaVinci Resolve is generally quite GPU dependent, but the XG Mobile was able to consistently
score higher despite the Thunderbolt setup having the more powerful desktop graphics
card.
The Thunderbolt setup has an even bigger defeat in Adobe Premiere, and then a smaller difference
in Adobe Photoshop, but regardless it’s a win for the XG Mobile in these three creator
applications.
So despite the desktop card being more powerful on paper, I just can’t recommend this setup
to anyone looking to purchase a Z13.
The only exception would be if you’re super serious about 4K gaming and maybe you’re
playing games that don’t have poor 1% lows.
But even then you’d still be dealing with all of the other negatives mentioned.
I just don’t think it’s worth it for anyone.
Are ASUS doing this to sell more XG Mobiles?
Probably not.
I mean they’re extremely difficult to actually get your hands on for one thing.
Offering a device like this that can use either eGPU setup is an extremely niche product.
Is it possible that ASUS can fix the remaining issues with the Z13 and a Thunderbolt eGPU
setup?
Absolutely, but at this point I’m not really too confident.
I’ve spent months of time troubleshooting this stuff with them and I’m just kind of
over it, and I mean this is hardware that you can buy right now.
The problems don’t seem to be just for me either.
A member of my Discord server mentioned that they bought the Z13 and tried to use it with
an RTX 3090 in the Aorus Gaming Box, and they couldn’t get it to work at all.
I believe they ended up returning it, and that matches my experience too, all sorts
of random problems with Thunderbolt.
Now that said, the XG Mobile from ASUS worked flawlessly in my own testing.
So yeah long story short, I would definitely recommend that over a Thunderbolt solution.
So now that we know that the XG Mobile is the way to go, ASUS actually offer it in both
AMD and Nvidia configurations.
Find out which is better in this video over here next.
I’ve compared AMD’s best RX 6850M XT against Nvidia’s RTX 3080, but again like this video,
there are problems to be aware of, so I’ll see you in that one next!