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Apr 12, 2001
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Using an iPhone 12 in Dual SIM mode throttles the cellular data speed to 4G LTE, according to an Apple Sales FAQ shared with retailers and carriers.

Screen-Shot-4.jpg

All 5G iPhone 12 models support Dual SIM mode, which refers to the ability to switch between a SIM card and an eSIM operating on independent numbers and/or carriers. However, an image of a training document from Apple's Sales Web resources called "What you need to know about 5G on iPhone" and posted to Reddit suggests the iPhone 12 will not support 5G on either line when Dual SIM mode is active. The FAQ reads:
"Does 5G work with Dual SIM?"
When using two lines in Dual SIM mode, 5G data isn't supported on either line and will fall back to 4G LTE. If customers are using eSIM only and are on a 5G-supported carrier and service plan, they'll have 5G access.
The document suggests that only by disabling one SIM or the other will 5G speeds be available – a limitation that, if confirmed, will come as a blow to iPhone 12 customers who intended to use separate work and personal lines, for example.

5G-dual-sim-incompatible.jpg

On the bright side, this incompatibility could be a software issue, and therefore something Apple could resolve down the line. Indeed, the Reddit user who posted the above image claims that an update coming later in 2020 will enable 5G when using a Dual SIM mode.

This information is allegedly revealed in Apple's internal training documents, but 5G is not anywhere mentioned in Apple's Dual SIM support page, which was last updated on September 26. We've reached out to Apple to clarify the matter and will update this article if we get a response.

(Thanks, De Paul Sunny!)

Update: MacRumors has received independent confirmation that the documentation is genuine.

Article Link: iPhone 12 Models in Dual SIM Mode May Not Run at 5G Speeds, At Least Initially [Update: Confirmed]
 
Last edited:

Malus120

macrumors 6502
Jun 28, 2002
356
571
That's pretty unacceptable if true, and if its unfixable is likely to be a deal breaker for a small but important minority of power users (myself included).

If this is anything more than just an initial software bug (AKA if this is a hardware limitation) I really have to question whether or not the iPhone 12 is ready for prime time.
 
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ian87w

macrumors 68030
Feb 22, 2020
2,847
3,595
Indonesia
That's pretty unacceptable if true, and if its unfixable is likely to be a deal breaker for a small but important minority of power users (myself included).

If this is anything more than just an initial software bug (AKA if this is a hardware limitation) I really have to question whether or not the iPhone 12 is ready for prime time.
Maybe 5G itself is not really ready, but seems like Apple had deals with the carriers, thus the push for 5G now.

If it's not a hardware limitation, then maybe it's an artificial limitation put by carriers like Verizon so customers wanting full 5G performance (and why not? They already paid for it) must use the phone exclusively with that specific carrier. It could be something similar to some AT&T plans not allowing hotspot.

So could be real technical limitation, or Apple bending over for the carriers, or both. Thus the risk of being on the bleeding edge.

I remember the old days where dual SIM Android phones only support 3G/LTE on SIM1, while SIM2 is stuck on 2G, for so long. There's always an excuse like how dual 3G/4G stand-by modems will use too much power. It's not until countries start to shut down their 2G networks that magically the technology caught up. Now we have cheap Android phones capable dual VoLTE on both SIM 1 and 2. Magic. :D
 
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Kimjongjohan

macrumors member
Jul 19, 2017
46
22
One question: Why? Seems like a really unwise priority, if it's a software limitation. If this is caused by hardware limitations, i guess they should have waited to release a 5G phone...
 
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ckater

macrumors newbie
Jan 27, 2010
10
37
Maybe I read the notice wrong but doesn't it state, that I *would* work if using (only?) eSIMs? So it would be a nice push to switch both SIMs to eSIM, if possible (me until using only one eSIM). Did you read it the same way?
 
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ani4ani

macrumors 68000
May 4, 2012
1,657
1,489
UK
Seems a little ominous to me; surely if it was a current limiation only, the answer above would reflect that, e.g. "Presently 5G is not supported in dual SIM mode, but will be made available in the future.....blah blah?"
 
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iGeneo

macrumors 6502a
Jul 3, 2010
824
1,519
Here comes the “power users” that must have the already sparse 5G coverage at all times. 🙄

I personally use dual sim for international travel, it is a non-issue.

And of course... we will have many that claim it is a “deal breaker”
 
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itsmilo

Suspended
Sep 15, 2016
3,985
8,721
Berlin, Germany
On one hand wtf on the other hand I just spent 6 hours on a train across Germany yesterday and 80% of the time I had EDGE or nothing so even LTE would be welcome everywhere before talking 5G which will probably roll out nationwide in like 3 or 5 years. Also 5G is pretty uninteresting with our limited data plans. I am sure as hell not gonna stream movies or download songs on mobile data
 
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ksec

macrumors 68000
Dec 23, 2015
1,714
1,814
Here comes the “power users” that must have the already sparse 5G coverage at all times. 🙄

I personally use dual sim for international travel, it is a non-issue.

And of course... we will have many that claim it is a “deal breaker”

Most people would have expected 5G to work on at least one SIM.

Unless the issue is fixed, you are now facing the option either using 5G or dual sim.
 
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Jmausmuc

macrumors 6502a
Oct 13, 2014
760
1,284
Here comes the “power users” that must have the already sparse 5G coverage at all times. 🙄

I personally use dual sim for international travel, it is a non-issue.

And of course... we will have many that claim it is a “deal breaker”
Good for you. I use dual sim 24/7 for work so the biggest feature of the iPhone 12 won’t work for me at all.
I have the right to be disappointed.
 
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SW3029

macrumors regular
Sep 22, 2019
138
446
Things like this are to be expected with the first-gen 5G iPhone. There are bound to be software or hardware limitations with tech related to 5G in the iPhone. It's why I'm waiting for the next iPhone to upgrade, which is only 11 months away.
 
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Pagemakers

macrumors 68030
Mar 28, 2008
2,693
1,030
Manchester UK
Here comes the “power users” that must have the already sparse 5G coverage at all times. 🙄

I personally use dual sim for international travel, it is a non-issue.

And of course... we will have many that claim it is a “deal breaker”
You do realise, if reported correctly you won’t get 5G on any sim? IE your 5G iPhone is in effect a 4G iPhone?
 
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Jmausmuc

macrumors 6502a
Oct 13, 2014
760
1,284
Order is now cancelled, sticking with XS for another year. Disappointing because I was looking forward to some new tech, but since I don’t take many pictures, the iPhone 12 already felt like only a smalll update.

i would not be able to use 5G at all, because I use dual sim 24/7.

I am waiting for the next iPhone with hopefully real 5G (including international UW) support, 120hz and a smaller notch. That will feel much better
 
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InGen

Contributor
Jun 22, 2020
172
523
This is likely as a result of the software priority system Apple is building into iOS that naturally switches between 4G & 5G depending on the kind of app or task you are doing
 
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Jmausmuc

macrumors 6502a
Oct 13, 2014
760
1,284
I am sorry but the iPhone 12 is a bull...t phone through and through. Same camera sensor, no touchID (how to even use this with a mask?!), no USB-C, no 120Hz, 5G no mmwave outside US, 5G not for Dual SIMs. So I get what? A cool new blue color in an iPhone 5/iPad like casing? For $1000?
I agree 100%. I can’t understand why demand is supposed to be so high.

Maybe it’s people who just want to give themselves something nice during all of this COVID mess... at least that was m reason.

I think the 12 just sucks. I was 100% seton upgrading and even stuck to it when they announced no 120hz, not even 90hz, same big notch, no USB-C and so on.
But not being able to use 5G at all because I don’t want to carry a separate work phone is too much.

Im not getting this phone.

Apple won’t care, they will still sell enough but I am much happier this way.

Really disappointing year though, I wanted to get the new Watch and the new iPhone, now I’m getting nothing.

Maybe I am getting an ARM Mac now, at least that will hopefully feel like a real upgrade.
 
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