Originally Posted by wizard69
Frankly I'm still wishing for an XMac equivalent. That is a machine with one GPU card and a desktop processor all for $1250 or so. Such a machine would shake up the PC market and almost assuredly get my money.
You can see the state of the PC market here:
The average unit price of PCs is under $600 - less than half Apple's average. Apple makes more profit from PCs than the next 5 PC vendors combined. I'm sure they'd convince some PC desktop owners across to the platform but they already own the premium segment because of the iMac and it would be silly of them to sell a quad-i7 with a 7970 for $1250 and just give away a display sale to Dell or HP when they can sell a quad i7 with a 780MX or Radeon and make as much as double that.
The desktop PC market cannot be shaken up. They can't do it with $600 PCs so they can't possibly do it with $1250 PCs. They said they're using Xeons and FirePros, they'd have worded it differently if there was any chance of there being desktop components. From a consumer point of view, it would be a nice option but I don't think it would do anything for Apple.
Originally Posted by v5v
I've been told that even Thunderbolt 2 is only about one-THIRD the bandwidth of a PCIe slot, so external boxes are not really suitable for things like super-high-end graphics cards, and that even cards with lower bandwidth requirements may be a problem when you need a few of them. The six ports on the Mac Pro don't necessarily mean that there are six discrete busses, or even more than one.
I've also heard there are issues with drivers for many graphics cards. Is that a situation that's unique to placing them in an external enclosure, or is that a problem that would exist even if the Mac Pro had internal PCIe slots?
Anyone able to confirm or refute this?
PCIe slots don't all have the same bandwidth but Thunderbolt 2 is equivalent to a PCIe 2.0 x4 slot. The old Mac Pro had two x16 and two x4 with a GPU taking up the first x16.
This new Mac Pro essentially gives you six x4 instead of one x16 + two x4. It's the same overall bandwidth but distributed differently. A redesigned Mac Pro with PCIe 3 slots would have offered more bandwidth per slot but the extra bandwidth doesn't really get used in practice and if you had two GPUs, you'd be stuck with just two x4 PCIe 3, which is fine speed-wise but some people would run out if they wanted a RAID card too. Audio processing is very low bandwidth. Video is higher but much fewer streams. Thunderbolt 1 might have had some bottlenecks but they didn't really show up much in a whole variety of tests. TB2 shouldn't have any real-world problems.
Here's a Red Rocket over TB:
1/2 res playback of 5K with real-time export. In workstations, it's the same performance:
"WITHOUT A REDROCKET: I can edit a 5K project without a REDrocket on CS5.5 in realtime by playing footage back between 1/8 or 1/16 resolution and take maybe 45 minutes to export a 3 minute video
WITH A REDROCKET: I can edit with a REDrocket on CS5.5 in realtime by playing footage back at 1/2 resolution and take about 3 minutes to export a 3 minute video."
One of them runs fine over TB1, so two should be ok in a TB2 chassis.
Running GPUs isn't ideal over TB but shouldn't be necessary with two high-end GPUs internally anyway. With the right drivers, TB2 bandwidth would be enough.
Originally Posted by v5v
Y'know Wiz, I've really enjoyed this exchange but I challenge you to back away from your insulting tone towards users until you've walked a mile in their shoes.
That's the best way to do it because you're a mile away and you have their shoes so what's the worst they can do?
Originally Posted by PhilBoogie
Yep, 6 ports, but on two busses. Phil said so during the keynote.
The 6 ports have 3 controllers but bandwidth contention isn't an issue here. This page explains some differences:
"1. PCI is a bus, whereas PCI Express is a point-to-point connection, i.e. it connects only two devices; no other device can share this connection. Just to clarify, on a motherboard using standard PCI slots, all PCI devices are connected to the PCI bus and share the same data path, so a bottleneck (i.e., performance decrease because more than one device wants to transmit data at the same time) may occur. On a motherboard with PCI Express slots, each PCI Express slot is connected to the motherboard chipset using a dedicated lane, not sharing this lane (data path) with other PCI Express slots. Also, devices integrated on the motherboard, such as network, SATA, and USB controllers, are usually connected to the motherboard chipset using dedicated PCI Express connections."
Every one of the 6 Thunderbolt ports should be able to sustain PCIe 2 x4 speed regardless of what any other device is doing. The only bottlenecking that would occur is while daisy-chaining.