iMac Pro's SSD, RAM & Thunderbolt ports questions

[bxs]

Subject: iMac Pro's SSD, RAM & Thunderbolt ports questions

Is the SSD capacity divided between two discrete modules ?
such as

1. 2x 512 GB for a 1TB size
2. 2x 1TB for a 2 TB size
3. 2x 2TB for a 4 TB size
4. Are the modules soldered down ?
5. If 2 modules are used are they somehow striped or what ?

How many RAM slots are there ?

1. Is it 2 or 4 slots
2. Is it true that if RAM needs upgrading from the 32 GB default this can be done by Apple service store ?

How many distinct data paths are the 4 Thunderbolt ports providing much like we have on the MP6,1 ?

1. 1 path
2. 2 paths
3. 4 paths

Thunderbolt Bridge
Will the Thunderbolt Bridge feature be available for connecting the iMac Pro to say a MP6,1 ? I ask as we connect our MP6,1 office machines this way as a poor-man's 10GbE for fast data transfers between the office Macs and it works very well for us.

None of the above are in any way issues affecting a 'buy' decision.

Thanks... ​

 

[bxs]

I posted my questions on iFixit the other day and got an answer for the "How many RAM slots". The answer was 4.

 

[bxs]

Just had a response to my SSD and Thunderbolt data paths on iFixit site where I had posted my questions... Here's the response...

"The SSD is comprised of two modules. They are removable, but are paired to the original logic board and won't work if moved to another iMac Pro logic board. I suspect this pairing will make third party replacement difficult or even impossible.

https://imgur.com/a/RjqwA

The system has two Thunderbolt controllers, each supporting two ports. Each controller is connected via PCIe 3.0 x4. Unlike the MacPro6,1, the PCIe doesn't run through a PCIe sharing switch to split the path.

Some other interesting tidbits are that the Vega GPU is integrated into the logic board and the system power supply is a 500 watt."

 

[rraven]

J
"The SSD is comprised of two modules. They are removable, but are paired to the original logic board and won't work if moved to another iMac Pro logic board. I suspect this pairing will make third party replacement difficult or even impossible. ...

Some other interesting tidbits are that the Vega GPU is integrated into the logic board and the system power supply is a 500 watt."

Wow. I can't say that I've had great experiences trying to use third party SSDs in my MacBook Pros and I'm not sure that I would try it again but this is still a scary level of "integration."

I hope that the GPU integration doesn't have an impact on the frequency of upgrade cycles.

Thanks for tracking this information down.

 

[CWallace]

The T2 chip acts as the controller for the SSD pair and encrypts the data which is why they can only be read by the iMac Pro they were initially installed in. The T2 chip also handles FileVault encryption (if you want to be even more secure). The T2 chip is directly connected to the DMI which has 4 PCI-e lanes and so the SSDs have 4 PCI-e lanes worth of bandwidth.

The twin SSDs are presented to the OS as a single logical unit so you will not be able to split them like you can a Fusion drive.

And we know from the artist renderings that there are four RAM modules.

 

[Earl Urley]

The 10 GB Ethernet is connected to a PCIe 2.0 x4 bus.

The GPU is connected to a PCIe 3.0 x16 bus.

Power Supply is 500W, input can be 90-250 VAC.

The T2 chip runs iBridge, which takes over functions formerly provided by SMC chip, also is responsible for EFI booting, secure enclave, live encryption of the SSDs, other functions.

The iMac Pro can be booted to DFU mode, similar to iOS devices, for upgrade of iBridge. You need to run Apple Configurator 2.6 or higher to do this. Probably replaces BootROM used in older Macs.

 

[Joe The Dragon]

The 10 GB Ethernet is connected to a PCIe 2.0 x4 bus.

The GPU is connected to a PCIe 3.0 x16 bus.

Power Supply is 500W, input can be 90-250 VAC.

The T2 chip runs iBridge, which takes over functions formerly provided by SMC chip, also is responsible for EFI booting, secure enclave, live encryption of the SSDs, other functions.

The iMac Pro can be booted to DFU mode, similar to iOS devices, for upgrade of iBridge. You need to run Apple Configurator 2.6 or higher to do this. Probably replaces BootROM used in older Macs.

so storage and network over the DMI bus??? and raid 0

 

[CWallace]

so storage and network over the DMI bus???

Yes. DMI replaced the traditional Northbridge / Southbridge. DMI 3.0 supports an 8 gigtransfer per second transfer rate per lane with a total of four lanes at 3.93 GB/s combined.

and raid 0

The two SSDs are presented to the OS as a single logical drive so it's effectively RAID 0 in terms of configuration, if not also implementation.

 

[bxs]

Yes. DMI replaced the traditional Northbridge / Southbridge. DMI 3.0 supports an 8 gigtransfer per second transfer rate per lane with a total of four lanes at 3.93 GB/s combined.




The two SSDs are presented to the OS as a single logical drive so it's effectively RAID 0 in terms of configuration, if not also implementation.

So having the 2x SSD modules as RAID0 is what gives us close to 4 GB/s data rates, right ?

...and the Processor reading/writing to memory (RAM) is at least some 5x faster than what we will get from the RAID0 SSDs, right ?

 

[CWallace]

So having the 2x SSD modules as RAID0 is what gives us close to 4 GB/s data rates, right?

Effectively yes - the dual-SSD configuration allows simultaneous reads and writes which does significantly increase the performance of each.

...and the Processor reading/writing to memory (RAM) is at least some 5x faster than what we will get from the RAID0 SSDs, right ?

The maximum memory bandwidth for the W series Xeons is 85.3 GB/s.

 

[bxs]

Effectively yes - the dual-SSD configuration allows simultaneous reads and writes which does significantly increase the performance of each.




The maximum memory bandwidth for the W series Xeons is 85.3 GB/s.

The 85.3 is the bandwidth so the one-way read or one-way write will be at 1/2 of this, right ? If this is correct then the memory read and memory writes will be 10x that for the SSD, and will result in i/o wait times being 1/10 of that for SSD when writing data to the RAM-based kernel buffer cache. I'm banking on this as I will have 128 GB RAM in my iMac Pro and as such the RAM-based kernel buffer cache is far better to use than the SSD when there's insufficient RAM available for the buffering data to/from SSD. My workload i/o is directed at external high-speed RAID5 media and not the internal SSD which I've purposely configured too be quite small at 1 TB.

 

[Marx55]

RAID0 for all iMac Pro? What SSD model inside iMac Pro (4 TB) shows at
"Apple - About This Mac - System Report - Hardware - Storage - Physical Drive - Device Name"?

For instance, iMac 5K 27-inch shows "APPLE SSD SM2048L", which stands for SaMsung SSD 2,048 GB (2 TB). Thanks and Happy Christmas!

 

[Chaszmyr]

The T2 chip acts as the controller for the SSD pair and encrypts the data which is why they can only be read by the iMac Pro they were initially installed in. The T2 chip also handles FileVault encryption (if you want to be even more secure).

Does this mean if the iMac Pro suffers a logic board failure that both the internal SSD and any Filevault backups become completely unreadable?

 

[kgelner]

RAID0 for all iMac Pro? What SSD model inside iMac Pro (4 TB) shows at
"Apple - About This Mac - System Report - Hardware - Storage - Physical Drive - Device Name"?

For instance, iMac 5K 27-inch shows "APPLE SSD SM2048L", which stands for SaMsung SSD 2,048 GB (2 TB). Thanks and Happy Christmas!

My iMac Pro shows a device name of

APPLE SSD AP4096M

(4 TB storage)

So I don't think it's Samsung given that designation...

 

[danielwsmithee]

My iMac Pro shows a device name of

APPLE SSD AP4096M

(4 TB storage)

So I don't think it's Samsung given that designation...

Apple has been using SAMSUNG raw flash and its own custom built controller for some time. So the flash parts are Samsung, but the controller is not. Each flash module likely has Samsung flash, an Apple Controller, and some RAM. Each module is than connected to the Apple T2 chip which presents the whole thing as a single logically volume to the OS.

It looks like this shares many of the components of the new MacBook Pro, which I think is slightly different from what is used on the current iMac 5K.
[doublepost=1514940553][/doublepost]

Does this mean if the iMac Pro suffers a logic board failure that both the internal SSD and any Filevault backups become completely unreadable?

If FileVault is enabled than yes. It remains to be seen if your FileVault password would be enough to decrypt the drives after a LogicBoard replacement.

 

[Marx55]

Apple has been using SAMSUNG raw flash and its own custom built controller for some time. So the flash parts are Samsung, but the controller is not. Each flash module likely has Samsung flash, an Apple Controller, and some RAM.

Thanks for the replies. APPLE SSD codes are

AP: Apple
SM: Samsung
TS: Toshiba

But Apple is not really Apple. Apple does not make SSD. In the case of iMac Pro, it seems that Apple SSD is indeed SanDisk inside, at least for 1TB model (APPLE SSD AP1024M), as shown by iFixIt:

iMac Pro Teardown
SanDisk SDRQF8DC8-128G (four per card, two top and two bottom, for a total of 512 GB × 2 = 1024 GB)
https://www.ifixit.com/Teardown/iMac+Pro+Teardown/101807