Apple Silicon Mac Pro uses PCIe switches to support all slots
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Apple Silicon Mac Pro uses PCIe switches to support all slots
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Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#2What is the consequence of this? Does it limit the theoretical ability to add GPUs?
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#3Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#4What is the consequence of this? Does it limit the theoretical ability to add GPUs?
If you add multiple GPUs to the same PCIe switch, their bandwidth to main memory of the SOC will be shared. For some use cases that bandwidth was already the bottle neck.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#5What is the consequence of this? Does it limit the theoretical ability to add GPUs?
You already can't add GPUs but since there's only 16 real lanes and a GPU can use 16 lanes it could cause issues.
I would think this would lead to bottlenecks for instance if you were trying to write to two different 16x PCIe SSD RAID cards simultaneously.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#6Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.
Of course Apple positions this as a proper workstation.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#7What is the consequence of this? Does it limit the theoretical ability to add GPUs?
Actually, no. It only limits the available I/O bandwidth to those GPU(s), that is, data transfers from and to the CPU will be far slower. You'll notice in games when the "loading next level" screen takes longer, that's usually a large geometry and texture copy to the GPU.
As an extreme example, when and where it was/is still viable, cryptocurrency mining operations use external PCIe cases with lots of slots, attached to only a few or even just one lane per case. For their purpose this was still viable, since mining uses very little I/O from/to the GPU, essentially only a small block of setup data into the GPU ("try hashing this block, vary those bytes within that range, report when result matches this pattern", a few kB) and a few bytes of results out ("found a match, varied bytes were as follows").
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#8Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.
The new Mac Pro can be rack mounted. It has PCIe gen 4 for audio and video I/O, networking, and storage cards.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#9Apple Silicon is low-power low-end laptop hardware. Of course their I/O capabilities are limited, because their users do not need lots of I/O. If you are looking for stuff with lots of I/O capabilities you have to buy proper server hardware.
Of course Apple positions this as a proper workstation.
I remember being downvoted for saying this is essentially a phone CPU and motherboard, just without consideration for constraints imposed by the phone's footprint. It means it can be designed with higher TDP in mind etc.
and yet, Apple charges for it as if it was a real workstation equipment rather than a phone in a massive enclosure.
Re: Apple Silicon Mac Pro uses PCIe switches to support all slots
#10Earlier quoted context omitted.
Of course Apple positions this as a proper workstation.
I remember being downvoted for saying this is essentially a phone CPU and motherboard, just without consideration for constraints imposed by the phone's footprint. It means it can be designed with higher TDP in mind etc. and yet, Apple charges for it as if it was a real workstation equipment rather than a phone in a massive enclosure.
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