More on the Thunderbolt cable availability front

According to industry insiders, there's no crisis in finding Thunderbolt cables, despite my personal experience of the other week. But the cables may remain specialty items for a while.
Written by David Morgenstern, Contributor

According to industry insiders, there's no crisis in finding Thunderbolt cables, despite my personal experience of the other week. But the cables may remain specialty items for a while.

Last week I recounted the trouble I had finding a cable for my new 4TB Thunderbolt array. The shrink-wrapped package had to be walked from the back room of a local Apple Store after some consultation among the sales staff.

Several readers and developers contacted me with some thoughts on the cables.

These Thunderbolt cables aren't the run-of-the-mill cables we're used to. Currently, I understand that there are third-party cables undergoing qualification, however, the cost of the cables will remain high, according to a video engineer who declined attribution. He said that each cable is individually trimmed and calibrated to guarantee 10-Gbps throughput.

Several readers said that they had sighted Thunderbolt cables on shelves in various retail settings, such as Frys and various Apple retailers. One reader suggested that there had been a run on the cables shortly after the technology's introduction and various technical managers and developers had purchased the cables whether they had a Thunderbolt peripheral or not.

There was the suggestion that the cost of Thunderbolt cables was in-line with other high-speed cables such as external Mini SAS (Serial Attached SCSI) and Infiniband, both of which have been available for years now. Now, I can understand the high cost of these cables, which are used by specialty, high-performance applications. But Thunderbolt?

The whole point of Thunderbolt is to leapfrog slower performance from "consumer" technologies like USB 3, which is now branded as "SuperSpeed USB." One or more Thunderbolt ports can now found on millions of Macs in the wild, but it appears that peripheral vendors are moving slowly and letting the market grow.

The Thunderbolt PHY is the same as a mini DisplayPort PHY. But the cables aren't the same. My MacBook Pro uses the Thunderbolt port as a mini DisplayPort for video out, you can plug in a mini DisplayPort adapter that translates to other video standards such as DVI, HDMI or VGA.

However, this isn't necessarily making the after-market situation around cables any clearer. The video engineer believes that there is still a lot of confusion about Thunderbolt cables.

A Thunderbolt cable cannot act as an mDP cable. An mDP cable cannot act as a Thunderbolt cable. Many no-name dongle suppliers say their HDMI or DVI or VGA adaptors are Thunderbolt compatible. They are merely mDP compatible.

According to Apple Support documents, there are restrictions on getting power from a Thunderbolt cable to a device, and where you can connect a display in the chain. It's an echo of the termination issues with SCSI that dogged us in the early days of the Mac.

Only the device directly connected to your Mac can get power from the Thunderbolt port. The rest of the devices in the chain must be powered by separate power adapters.

A DisplayPort device can be part of the chain, but it must be at the end. For example, if you want to connect both a Thunderbolt hard disk and a DisplayPort display to your Mac, connect the display to the hard disk and then connect the hard disk to your Mac.

On several discussion boards, I noticed a reports of problems when connecting multiple adapters into the Thunderbolt chain, such as going from a mini DisplayPort to DVI adapter to a DVI extension cable and then to a DVI to HDMI adapter. Yet another third-party cable opportunity, it appears.

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