
Hardware Hackers Create a Modular Motherboard - naish
http://www.wired.com/gadgetlab/2009/08/modular-motherboard/
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natemartin
This is really interesting. I definitely want to read more, because I've got
some questions about it. I wonder if there's a limit to how many can be
plugged in before you start seeing power problems on the downstream
processors, and how it routes information between processors.

Definitely intriguing though!

Edit: Unfortunately, there doesn't seem to be much documentation on their
website. A lot of talk about open source hardware, but I don't see any
schematics, datasheets, etc. Oh well. Hopefully they'll be adding that soon.

~~~
Retric
_Each X Machina module has a 72 MHz processor (currently an ARM chip), a solid
state drive of 16KB and 128KB of storage in an EPROM (erasable programmable
read-0nly memory) chip. There’s also an LED for display output._

These are not going to suck down much power. They have around 1/1000th the
processing power of a 3Ghz quad core chip and 1/250th the RAM. If you want to
build a useful mesh like this then cooling is going to be the first concern,
followed by latency. The best design would be a back plane with these cards
inserted into the side. Add power at the top and cool down the sides with the
back plane for communication. But that's what a standard motherboard with
PCI-X slots look like so it's less interesting.

~~~
natemartin
Oh, I know these are very low power. But even if each board only takes 1 watt,
if you've got 40 of them you're talking the same power consumption as a laptop
CPU, but with a much longer distance for power delivery.

But I'm still curious exactly what the power is, what the resistance of the
power connections are, etc.

As you said, it gets more interesting when they're not in a backplane, so I
wanted to figure out what the constraints are.

Someone on one of their blogs linked to <http://www.xmos.com/> which is also
pretty interesting. It's a single chip with 4 cores, each of which can run 8
threads. And it takes care of all the switching between cores or even between
chips.

It doesn't have all the same features as this board does, such as the
dynamically switched power/signal pins, but same sort of idea.

Edit: In fact, the modularity of this is one of the more interesting aspects
of it to me. I'd like to see how they're switching pins between signal and
power dynamically. But, there's no schematics that I can find.

~~~
Retric
There is little problem in supplying power to a grid like this. It's related
to the classic _Given an infinite grid of 1 ohm risistors, what is the
resistance across a single diagonal? Well known answer: 2/pi ohms._
<http://answers.google.com/answers/threadview?id=92564>

Basically, as the size of the grid increases so do the number of paths to an
edge element. The practical limit relates to how much current you can drive
through a single, element, but you can always use more than one power
connector.

Edit: _USB connection it can support a 3 x 3 grid_ (500 milliamps * 5 volts /
9) ~= 0.3 watts. So 130 of them should equal a low power CPU.

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jwilliams
This is part of the theory behind PCIe - there is a spec for a PCIe "external
cabling". The idea is that you'll have your lanes cabled, and you can build a
computer out of modular parts (i.e. modular bricks).

(although the main driver at the moment seems to be the ability to plug a
decent video card into your laptop).

~~~
nazgulnarsil
why hasn't this idea taken off? instead of packing a high end graphics card
into a laptop where it is likely irreplaceable I'd rather have a dock for my
laptop that includes a bay for a better video card. hardcore gaming at home
(with an upgradeable part, low power consumption on the road.

~~~
jwilliams
Yeah. Dell used to support a dock with PCI (not PCIe) plus an extra hard
drive, and the usual port replication -- was great.

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srn
This project is interesting, given that it's open source and you can
dynamically add or remove units. As far as power goes, crank down the clock
speeds and any processor is going to run cooler. arm is also well known for
taking less power.

But about the whole changing your basic architecture, consider Tilera:

<http://www.itjungle.com/tlb/tlb082107-story02.html>
<http://www.theregister.co.uk/2008/09/23/tilera_cpu_upgrade/>

And it runs linux! ;)Granted it's closed and probably costs a bazillion, but
the big guys haven't exactly missed out on the memory bus being a bottleneck.

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kiba
Look like you can have your own cake and eat it too!

<http://www.liquidware.com/shop/show/IXM/Illuminato+X+Machina>

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mattyfo
Hmmm, modular, clusterable and able to reprogram each other. Is this the rise
of the borg?

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bkj123
very interesting. I wonder if this architecture would make for a good mpp
database appliance - something that is lean and very focused and somewhat
power hungry!

