PT Video Peripheral Advice BM vs AJA

[LDS]

Originally Posted by Pete Gates

I don't think you'll even get a Kona 4 running like that on its own, let alone with an HDX card. You'll need a TB3 expansion chassis to handle that card and it'll probably saturate even that, so you still won't reliably run an HDX card with it.

Cheers,
Pete

I have never had a problem running HDX2 and a Blackmagic Decklink card in the same TB2 sonnet enclosure. We would be talking two PCIe 2.0 x4 devices for HDX2 and a PCIe 2.0 x8 device for the Kona 4. All up, it is 8Gbps for downstream, and 8Gbps for upstream. TB2 has 20Gbps of bandwidth each way...

If we were talking GPUs, I definitely wouldn't want a x16 device sharing a thunderbolt bus bandwidth with anything else but video playback cards don't seem to work anywhere near as hard computing hard data into visuals.

[Pete Gates]

Originally Posted by LDS

I have never had a problem running HDX2 and a Blackmagic Decklink card in the same TB2 sonnet enclosure. We would be talking two PCIe 2.0 x4 devices for HDX2 and a PCIe 2.0 x8 device for the Kona 4. All up, it is 8Gbps for downstream, and 8Gbps for upstream. TB2 has 20Gbps of bandwidth each way...

If we were talking GPUs, I definitely wouldn't want a x16 device sharing a thunderbolt bus bandwidth with anything else but video playback cards don't seem to work anywhere near as hard computing hard data into visuals.

Your numbers are off I'm afraid, the TB2 one is correct but your PCIe 2.0 ones are completely wrong.

Pete

[LDS]

Originally Posted by Pete Gates

Your numbers are off I'm afraid, the TB2 one is correct but your PCIe 2.0 ones are completely wrong.

Pete

The official PCIe 2.0 spec is 500Mbps per lane. HDX is a PCIe 2.0 4 lane device. The Kona 4 a PCIe 2.0 8 lane device. My numbers are totally within spec. If anything, what I have suggested is the absolute upper limits of what those cards use, and the real world numbers will be less.

Are you perhaps confusing the base clock rate of PCIe 2.0 at 5.0Ghz, with the total bus bandwidth of PCIe 2.0 at 8Gbps for a 16 lane device? I'm sure Sonnet know a thing or two about this, which is why they have included two x8 PCIe 2.0 slots and one x4 2.0 PCIe slot in the TB2 enclosure. The suggested setup will work totally fine.

[Pete Gates]

Originally Posted by LDS

IWe would be talking two PCIe 2.0 x4 devices for HDX2 and a PCIe 2.0 x8 device for the Kona 4. All up, it is 8Gbps for downstream, and 8Gbps for upstream. TB2 has 20Gbps of bandwidth each way...

Gbps is gigabits/S not gigabytes/S. Here you're using it to signify both. GBps or GB/S is gigabytes/S

PCIe 2.0 x 16 is 8GB/s not 8Gbps, it's 80Gbps with TB2 being only 20Gbps

Originally Posted by LDS

The official PCIe 2.0 spec is 500Mbps per lane.

And here you're doing the same with Mbps, which is megabits/S. MBps or MB/S is megabytes/S. A PCIe 2.0 lane is 500MB/s not 500Mbps, it's 5000Mbps.

Originally Posted by LDS

Are you perhaps confusing the base clock rate of PCIe 2.0 at 5.0Ghz, with the total bus bandwidth of PCIe 2.0 at 8Gbps for a 16 lane device?

PCIe 2.0 x 16 is 8GB/s not 8Gbps, it's 80Gbps.

Originally Posted by LDS

I'm sure Sonnet know a thing or two about this, which is why they have included two x8 PCIe 2.0 slots and one x4 2.0 PCIe slot in the TB2 enclosure. The suggested setup will work totally fine.

They certainly do, and it's common to have a set of PCIe slots where the total number of lanes needed to achieve saturation on all slots simultaneously is greater than the total number of lanes feeding among them all.

Thunderbolt 2 is essentially a PCIe 2.0 x 4 connection, so a PCIe 2.0 x 8 electrical connection video card such as Kona 4 will not be able to achieve its maximum performance over that connect. That may not necessarily even be a problem in your usage case, YMMV.

Pete