Fiber On Your Motherboard...Soon!

km790816 writes: "In this post I joked about wanting an optical bus on my PC. In the last week I've seen two articles from The Register and EETimes discussing the real possibility. Both mention high bandwidth and lower heat and power usage. Sounds good to me."

Comments

Cool, people finally starting to publish

[bstrahm]

I love hearing that people are finally starting to publish intentions. I have been hearing rumors about this for a year or so now, since an EVP where I worked started talking about plugging a Fibre into the side of the microprocessor (and he wanted to own that connection)
As is normal, he missed completely thinking it would be a 10GbE fiber for networking, rather than a 40+GB connection to main memory...

The comments on working on the I/O side of the processor were right on (I read the EETimes article, rather than the Register article to get "real" facts ). For years Sun was known for having the slowest RISC processor in the business, however they had the fastest boxes. No one seemed to understand this, until they realized that they were running multiple 128 bit memory buses at rather good clock rates. That was better than 10 years ago, and just now we are starting to see memory busses approaching this level in their competitors hardware.

Re:Not a troll

[RollingThunder]

While most folks are correct in that the biggest latency source is the drives right now, there is a fair bottleneck on the RAM to CPU bus. I think it's up around a 8:1 ratio right now (4:1 if you have a 266 MHz FSB), which means that your CPU can spend a large portion of its time waiting for data from memory.

True, that's what the L1 and L2 cache are supposed to prevent, but some apps (games, mostly) blow through that cache without even thinking about it. WWIIOnline, for instance, gets bitchy with only 256MB. It's only happy once you have 512MB. How long will even a 4 MB on-die cache last?

If we can increase the speed that we can toss bits between the CPU and RAM, we'll reduce one more sticking point (and RDRAM, expensive as it is, was meant to do that), and higher framerates for all! :)

About buses

[petis]

The reason that buses that uses photons as the data carriers are coming up is quite interesting. The good thing with light (photons) are that photons are 'bosons', which amongst other things means that they do not interact with other photons. Good for transporting data, since noise is not a problem.

Electrons, on the other hand are 'fermions', which means that they interact strongly with other electrons. That is good for logic (since the whole point is to interact..), but is a problem for transports. (Cross talk etc)

From a power consumption point of view, using currents/voltage in a wire to send a logic one ore zero has some really severe problems. The wire itself introduces a resistance, capacitance and inductance which are non neglectible, at least not for long wires (buses) or high frequencies. IIRC, R ~ sqrt(f) for high frequencies, which leads to signal distortion, power loss, and ultimately an upper limit to the data rate. This is probably one of the reasons that research and development is going on in this area.

SCSI, optical

[sigwinch]

This would put SCSI on the skids. Right now SCSI is the only really fast interface commonly available between devices, but it's cost has kept it from becoming the standard. But if you could just plug in a fiber connection, you'd be rocking.

SCSI is rather physical layer agnostic. It already runs on at least four totally different electrical layers: high-volvage single-ended, high-voltage differential, low-voltage differential, fibre channel (which can be copper, despite the name). Optical SCSI would be just another physical layer. The real value of SCSI is that it is very nicely tailored to mass storage devices.

Another problem is that we'd still have the silicon-to-light translation bottleneck. i.e. and electrical signal from a pin on a chip needs to be converted to laserlight somehow. To make this truly work, you'd need a chip that reponds via light, ...

Yup, that's the real challenge. Speaking from personal experience with optical chip modules, getting fiber/light to the chip is major pain in the ass. The mechanical design challenges are significant and obnoxious.