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You can also stack SRAM bumplessly using the wireless ThruChip Interface: https://en.wikichip.org/wiki/thruchip_interface https://en.wikichip.org/wiki/thruchip_

by Sephr 5y ago

You can also stack SRAM bumplessly using the wireless ThruChip Interface: https://en.wikichip.org/wiki/thruchip_interface https://en.wikichip.org/wiki/thruchip_interface

Escapado 5y ago
Interesting technology. Is everyone using it? And if not (I recall tsv being used a lot) then why? The wiki entry paints a very positive picture here.
- jleahy 5y ago
  Large size and poor thermals, if I had to guess.
- Sephr 5y ago
  Apparently Japan withdrew funding from the company developing this[1]. Hopefully another company can pick this up eventually to see if its worth using. iirc the fraud was financial and the tech was legit, but please correct me if I'm wrong. 1. https://fuse.wikichip.org/news/1204/pezys-future-is-uncertain-as-japan-cancels-contract-kicks-out-4th-fastest-supercomputer-amid-fraud-charges/ https://fuse.wikichip.org/news/1204/pezys-future-is-uncertai...
jl2718 5y ago
I do not understand on-chip wireless. Why build an antenna for each channel? You could just multiplex high-impedance RF into any common wire with and it’s the same thing.
- monocasa 5y ago
  Because it works better. Two very close antennas and two halves of a transformer are just a matter of tuning and opinion.
  - kabdib 5y ago
    Is this affected by external magnetic fields, or other interference that a hard-wired connection is immune to? I'm not in the habit of waving magnets around near CPUs, but I worry about susceptibility to EMI and transients.
    - lazide 5y ago
      The only difference between a handheld magnet, radio waves, inductance, etc. is speed, precision, and magnitude. So in practice it is highly unlikely a handheld magnet is going to do anything for the same reason a cloud passing overhead is going to break a rock. The difference in air pressure is too low, the energy gradient too gradual, and it’s too far away anyway. Take the same aggregate amount of energy into a tank of compressed air, and use a jackhammer and that rock is dust in no time. Same physics principles; radically different impact in practice. Assuming the magnet you have isn’t the electromagnetic version of a tornado and you aren’t waving it around at several thousand RPM anyway.
      - zelon88 5y ago
        What about size? Does the advantage disappear if you need to bundle a large number of these on a chip?
    - canadianfella 5y ago
      You don’t need to worry. Smarter people have figured it out.
  - jl2718 5y ago
    Well, yeah, I’m with you, but, you don’t need a transformer. You need a HF short. That’s easy. You can hook up a common conductor any way you want, connect as many independent channels as you want, put a big resistor from signal to ground at each terminal, and it works the same but smaller and lower power. Make the wire slightly resistive if you are concerned about reflection loops. I can’t think of a situation where signal couldn’t be improved by some kind of conduction.
rbanffy 5y ago
I remember Sun working on wireless interconnects, but I think it was horizontal, inter-package

by Sephr 5y ago

You can also stack SRAM bumplessly using the wireless ThruChip Interface: https://en.wikichip.org/wiki/thruchip_interface https://en.wikichip.org/wiki/thruchip_interface

Escapado 5y ago

Interesting technology. Is everyone using it? And if not (I recall tsv being used a lot) then why? The wiki entry paints a very positive picture here.

jleahy 5y ago
Large size and poor thermals, if I had to guess.
Sephr 5y ago
Apparently Japan withdrew funding from the company developing this[1]. Hopefully another company can pick this up eventually to see if its worth using. iirc the fraud was financial and the tech was legit, but please correct me if I'm wrong. 1. https://fuse.wikichip.org/news/1204/pezys-future-is-uncertain-as-japan-cancels-contract-kicks-out-4th-fastest-supercomputer-amid-fraud-charges/ https://fuse.wikichip.org/news/1204/pezys-future-is-uncertai...

jl2718 5y ago

I do not understand on-chip wireless. Why build an antenna for each channel? You could just multiplex high-impedance RF into any common wire with and it’s the same thing.

monocasa 5y ago
Because it works better. Two very close antennas and two halves of a transformer are just a matter of tuning and opinion.
- kabdib 5y ago
  Is this affected by external magnetic fields, or other interference that a hard-wired connection is immune to? I'm not in the habit of waving magnets around near CPUs, but I worry about susceptibility to EMI and transients.
  - lazide 5y ago
    The only difference between a handheld magnet, radio waves, inductance, etc. is speed, precision, and magnitude. So in practice it is highly unlikely a handheld magnet is going to do anything for the same reason a cloud passing overhead is going to break a rock. The difference in air pressure is too low, the energy gradient too gradual, and it’s too far away anyway. Take the same aggregate amount of energy into a tank of compressed air, and use a jackhammer and that rock is dust in no time. Same physics principles; radically different impact in practice. Assuming the magnet you have isn’t the electromagnetic version of a tornado and you aren’t waving it around at several thousand RPM anyway.
    - zelon88 5y ago
      What about size? Does the advantage disappear if you need to bundle a large number of these on a chip?
  - canadianfella 5y ago
    You don’t need to worry. Smarter people have figured it out.
- jl2718 5y ago
  Well, yeah, I’m with you, but, you don’t need a transformer. You need a HF short. That’s easy. You can hook up a common conductor any way you want, connect as many independent channels as you want, put a big resistor from signal to ground at each terminal, and it works the same but smaller and lower power. Make the wire slightly resistive if you are concerned about reflection loops. I can’t think of a situation where signal couldn’t be improved by some kind of conduction.

rbanffy 5y ago

I remember Sun working on wireless interconnects, but I think it was horizontal, inter-package