Arduino Forum

Forum 2005-2010 (read only) => General => Bar Sport => Topic started by: Jeremy1998 on Dec 19, 2010, 09:30 pm

Title: Ponder This
Post by: Jeremy1998 on Dec 19, 2010, 09:30 pm
Why don't we use HDMI or something very similar in computers? I mean there are companies like Monster Cable (this is not spam, I promise) that have HDMI cables that claim to be capable of over 21GB/S (http://www.monstercable.com/productdisplay.asp?pin=4314)! I know they're expensive, but they sell them on eBay for like $30.  
Title: Re: Ponder This
Post by: AWOL on Dec 19, 2010, 09:32 pm
We do use stuff very similar.
They're called PCB tracks.

I know a guy who designs X-ray image processors.
His cards are all linked with professional, studio quality digital TV interconnects.
Title: Re: Ponder This
Post by: AlphaBeta on Dec 19, 2010, 09:35 pm
HDMI is actually 'just' 10.2 Gbit/s not 21 GByte/s (which is more than 16 times as fast).
The cable was rated for 21 Gbit/s :)

One can easily use HDMI with computers. My PC has a HDMI connector.
Title: Re: Ponder This
Post by: Jeremy1998 on Dec 19, 2010, 09:39 pm
Right, but that's for video. It would be really good for connecting nodes to make a supercomputer...
Title: Re: Ponder This
Post by: AWOL on Dec 19, 2010, 09:42 pm
Quote
Right, but that's for video

No, that's for digital data.
Quote
It would be really good for connecting nodes to make a supercomputer...
Depends on the architecture.
Good for short, point-to-point, lousy for bussed systems.
Title: Re: Ponder This
Post by: Jeremy1998 on Dec 19, 2010, 09:49 pm
True.

I don't know... I just got an idea when I was looking at cables for my TV.
Title: Re: Ponder This
Post by: AWOL on Dec 19, 2010, 10:01 pm
Besides, I think glass is still cheaper than copper.
And I'm not talking SPDIF.
Title: Re: Ponder This
Post by: jezuz on Dec 19, 2010, 10:58 pm
Plus wouldn't the bottlenecking be the hardware, not the interconnects?
Title: Re: Ponder This
Post by: cmiyc on Dec 19, 2010, 11:10 pm
There is nothing special about HDMI and its bandwidth.  The reason it has so much is because it is made up of multiple high speed serial lanes.  There are 3 lanes, each running 3.4Gb/s for a total of 10.2Gb/s.  

The underlying protocol is what makes it "HDMI" and is specifically targeted for audio/video.

If your interest really was, communication between computers then you'd want to look at Infiniband.  Generally it is used for intra-computer communication.  Up to 12 links can be combined giving a maximum throughput of 300Gb/s.  That is 12 Links each running about 25.7Gb/s.

Anyway, look at Infiniband.  Electrically very similar to HDMI but the protocol is design for interconnecting computers instead of TV.

http://en.wikipedia.org/wiki/InfiniBand
Title: Re: Ponder This
Post by: Divyanshu on Jan 05, 2011, 08:15 pm
Even though glass is cheaper than copper, it's very brittle and need the extra cladding on the cable.
Title: Re: Ponder This
Post by: cowjam on Jan 05, 2011, 10:54 pm
I thought the problem with supercomputers was clock speed rather than the bandwidth available defined by the physical property of whatever the buses are made of?

For every clock cycle of a 3Ghz processor light only travels 10cm. I'm under the impression this is why everything's multicore rather than just faster.
Title: Re: Ponder This
Post by: keeper63 on Jan 05, 2011, 11:03 pm
Quote
Anyway, look at Infiniband.  Electrically very similar to HDMI but the protocol is design for interconnecting computers instead of TV.


...and that's about all any mere-mortal can do. While the cost of Infiniband (and similar interconnect technologies) have come down in price over the years, they are still waaaaaaaaaay out of the price-range of an individual.

;D
Title: Re: Ponder This
Post by: cmiyc on Jan 06, 2011, 12:30 am
The cost of the interconnect isn't the prohibitive factor.  Any kind of hardware that can generate enough data to warrant a 4x 25Gb Link is going to be significantly more expensive than a couple of SERDES, Connectors, and Cables.