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Repair information for the Mac Studio, Apple's compact desktop computer.

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How many USB/TB controllers?

Does anyone know how many individual thunderbolt 4 and USB 3 controllers are in here.

I’m trying to determine the maxim attachment limits.

Update (01/11/2023)

For those who wonder I can now confirm a few things.

At least for the ultra. Let’s first mention that the M series chips, like apples later A chips, DO have USB controllers. It’s a logical, or soft controller implementation in the chip’s ISC but it’s still there.

Based on power draw testing the thunderbolt ports are individually powered. I don’t have 127 devices to test my theory, but I believe each port is solo control.

Second, the two usb A ports are shared; a single controller.

I guess hands-on puts it to rest.

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I can't say for certain, I would need access to good views of both sides of the logic board for one of these, plus the schematic, which I don't expect will make it into the wild any time soon. But here's what I can tell you based on the information I have from other Apple Silicon based Macs and the board hardware.

The 2021 14" MacBook Pro makes use of 1 Texas Instruments CD3217 USB C Port/Power Delivery Controller and 1 Thunderbolt Retimer per USB C port. Data lines for the Thunderbolt retimer go basically straight to the SoC (no other chips, just small basic components). As for how the SoC handles it, I can't say for sure. But there are no longer "Thunderbolt" controllers like you you see on Intel devices. Like so many other things that used to have dedicated controllers, its built into the "processor" (of whatever flavor– Pro, Max or Ultra).

I don't know that that will be much help to figure out your setup, hopefully it will mean you can consolidate some. But it's hard to say in practice.

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Thanks. Yes, that’s where my understanding was but nobody has been clear anywhere and I can’t get anyone else with a studio to actually torture it (understandably).

I have a Power ia system that is similar, in that the cpu includes two controllers and the board has four more.

I run three sets of JBSD arrays. A primary use, a delayed mirror, and a long term backup.

My problem isn’t connectivity, but power. I have yet to find a powered hub with more than 8 ports that provides enough power for a long string (20+ drives) under $100.

Apple appears to have solved this with the studio. Each port being independent.

What’s just looking for reassurance.


@lostinlodos - Its a one to one a given TB3 port goes directly to the SoC. I get it you need to manage the load! Just like I go about it with my MacPro. But unlike it the Intel systems have a PCH chip which then spilt the PCI lanes across which is what messes you up Apple doesn’t get stuck in that mess. It’s a direct drive to the SoC! Which was the point from the start!


@lostinlodos I would love to have one of these to play around with. But I don’t have any practical use for a machine like this and it’s definitely not in the budget. I’d just want to take it apart and map out the PCB.

Your predicament makes total sense to me. There’s usually plenty of bandwidth for data to go around. But I can see how you might run into power constraints. I don’t know what you’re running now, but I know Intel MacBooks can be really touchy about excess power draw out of the USB C ports. You’ll have to let us know how it goes when you it up and running!


@flannelist - the power issue is due to the USB chaining of drives off of a hub. This wouldn’t be an issue with the TB3 connection one for one as the throughput is higher than USB3.2


@alisha c

Exactly. I’m the issue appears to be the USB hubs don’t provide a full power output except to the dedicated charging ports. They also appear to pull off a fair bit of power from USB themselves.

I’m looking forward to trying out a new set of hubs and see what happens.

I’m definitely having power issues at the moment any way I pull the array. And I can’t begin to afford a rack system to match my setup. That would be triple the price of the studio.


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The SoC chip dictates how many are TB3 ports. The Ultra gets all four USB-C connectors as TB3, unlike the Max only has the rear ports as TB3 and the front ports are limited to USB3.2. Each TB3 ports are dedicated unlike the USB3.2 ports.

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Thanks. I follow that much. A better way to word it is how many actual controllers are included.

Eg, most of the recent Intel series supply 2 controllers (four ports) or one controller (2 ports)

Which equates to 254 or 127 devices

Early rumours during pre-release had suggest ultra would carry 2 or 4 TB4 controllers plus a usb controller.

Is there any clarification on this? As I have yet to see anything from apple or a developer.

Thanks again.


Again the chip is the clue! An Ultra is two Max chips bonded together. Which is why the Ultra has four TB3 and the Max two TB3. There is no hub logic or splitter’s.


Dan, thank you for responding again.

I think there’s a minor disconnect in thoughts.

The number of ports is only by history a clue. Intel macs use two ports per controller for usb, and 2 ports per Thunderbolt 3 controller.

I don’t see any indication this changed. But I wonder if we now get one port per controller or it remains two. M yes, I have found I can overload a single controller. I use a BOSD array, all under 4TB. All internal SATA and SAS via USB adaptor.

I found large quality hubs can have 2-4 controllers each. Making my collection of devices easily reach 127. When you add multiple keyboards, controllers, a graphical pad, mice, etc.

I currently have it spread over 6 ports.

I’m wondering if I could reduce the hub interconnects by using more ports. If so, I would be purchasing more smaller hubs.

I’m currently running into a bottleneck that’s causing drives to disconnect, due to power constraints.

Granted I could wait till the unit arrives. But I’d like to have the setup in place beforehand


@lostinlodos - Intel systems are radically different then Apples SoC chips. In the case of Intel the chip has only so many PCI lanes which is the bottle neck as a collection of lanes connect to a PCH chip (hub) to then be split out. So the collective devices need to share the upstream connection.

In the case of Apples M series chips used in the Studio Apple cleverly took a single SoC and bonded two together. In fact they had even visioned not only doubling but quadruple this bonding concept:

Max > Ultra > Extreme

But unlike Intel who increased the compute cores but held the PCI lanes mostly the same Apple is scaling both. In years past we described the architecture as asymmetric Vs symmetric on how the computer was designed. Apple has married these two concepts within the SoC!

So at the system there is no hub or spitters the TB3 port is direct. But the SoC version dictates how many TB3 ports it offers as the subunit (Max) only offers two. The Ultra offers four and if we see the Extreme it will offer Eight!!

So… you are over fixated on the failures of Intel’s design not to see how Apple novel approach lays waste to it. Even still what you do externally can still mess things up.

So you need to think how the data flows in your workflow.

As a photographer in my 2013 MacPro I compartmentalize my Boot drive as my OS & Apps leaving more than half of the internal 2TB SSD empty so caching, Virtual RAM & App scratch space have plenty of room and wear leveling is not constantly kicking in. I then have two external RAID drives one SSD the other HDD for my work files. The USB ports are strictly for the controls and data input from my cameras.


Hi Dan.

We’re still on two different topics. I’m aware of the port differences and why. USB is limited regardless of the chip implementation.

Though at this point I’ll just pull up the info when it arrives.


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John clark zal eeuwig dankbaar zijn.

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