Comment by londons_explore

2 years ago

On the apple cable... That circuit looks like a lot more than an e-marker. Why do we have a massive 105 pin BGA chip in there?

Does this cable run iOS or something?

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londons_explore

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artimaeis  2 years ago

It's an Intel Thunderbolt ReTimer chip.

https://youtu.be/LBWnb0ZIlEA?si=hgLg_TOa9zr42wpU&t=304

I can't find the 7040 specifically, but here's a similar 9040R chip: https://www.intel.com/content/www/us/en/products/sku/211299/...

  • londons_explore  2 years ago

    I understand having retimer (ie. active signal booster) chips midway along a long cable... But at the end of a cable a mere 2 inches from the place the signal is going to end up seems superfluous...

    Is it because the thunderbolt spec inherits timing parameters from PciE and it was hard to meet those with a long cable?

    • artimaeis  2 years ago

      Maybe someone else can say with certainty, but I will note that they chose a > 1m cable to image. Thunderbolt 4 cables <= 1m in length can be passive, Apple's 1m cable is only $69 USD.

      That probably explains the irregular pricing intervals stepping up from 1.8m $129 to 3.0m for $159. Though it's a very Apple thing to charge $30 for the extra 1.2m of cable. At least the complexity of the integrated circuit can explain that first jump.

      I'd imagine both the very-high bandwidth and the PCIe interop make necessary the retimers.

floxy  2 years ago

Yes, this is the question I was going to ask. Is that an Apple ASIC? Or something off-the-shelf? Crazy if it was an FPGA inside a cable, but maybe not with the price tag. We need to have someone dissect one of these to see if there are any markings on that. I supposed something this tiny is a wafer level chip-scale package. I can't seem to find any 105 pin BGAs at Octopart or Digikey, but it isn't easy to shop by pin count alone.