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Desktop Supercomputer - Design
My design criteria were as follows:
- 1. As many fast processors as possible.
- 2. Reasonably small footprint, ideally desktop/desk-side sized.
- 3. Quiet - this thing will be living in my home office.
- 4. Low cost!
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I had planned on buying a pre-built workstation from a company such as Sun, HP or maybe even Dell. However, after a lot of searching around on the 'net, I failed to find anything that met all four of the above requirements. There were a couple of systems that met 1 and 2 - but very rarely 3 - and never 4.
Seymour is designed to be a small but extremely powerful single box clustered computer. The 400mm cube shaped case contains four individual quad-core nodes linked together via switched Ethernet. To reduce cost and to ease repairs and future upgrades, standard ATX PC components have been used throughout the design. Because large or fast storage is not a requirement, only the first node (node 0) has a hard disk drive. The remaining three nodes network boot using the disk attached to node 0.
Each individual node is composed of the following hardware:
| CPU: | Intel Quad Core Q6600 2.4GHz S775 |
| Motherboard: | Gigabyte S775 Intel P965GMX ATX |
| Memory: | 2 x Kingston 512MB DDR2-667 CL5 Non ECC |
| Power: | Dabs Value AMD/P4 350W ATX PSU PFC |
Node 0 contains the following additional components:
| Disk: | Samsung HM1221HI |
| Network: | BlackBox USB-Powered Ultra-Compact Ethernet Switch (5 port) |
CPU
The cost versus performance of the Q6600 made it the obvious choice for Seymour, and it has so far proved to be an extremely capable processor. I've read reports that it can easily be over clocked to 3 GHz, but I have yet to try.
Motherboard
The Gigabyte motherboard was the cheapest I could find with support for quad-core CPUs and with on-board LAN and graphics.
Memory
1GB of memory per node is more than enough for my needs. I've used 2x512MB which enables the use of dual channel mode. My own tests of single versus dual channel performance suggest that it was a good decision.
Power
The power requirements for each node aren't huge. Intel claim that the CPU consumes 95 watts under load; I'm guessing that the motherboard adds a little bit to that. I simply choose the cheapest, lowest wattage power supply available at the time.
Disk
The nature of the software used on Seymour means that storage performance is not an issue. A 120GB 2.5. 5400rpm disk has been used. The decision to use a low speed laptop disk was made due to it small physical size and low power consumption.
Networking
BlackBox USB-Powered Ultra-Compact 100Mbit Ethernet Switch (5 port)
The interconnect will always be the main bottleneck in a clustered system. For this reason the software on Seymour has been designed such that very little communication is required between the 4 nodes. A single master process running on node 0 passes out work packages to 16 slave process (4 per node). Each work package is designed to take roughly 10 seconds to complete, at which point the result is communicated back to the master. By doing this, network communication is kept to an absolute minimum.
Using a 100Mbit switch rather than a faster one has several advantages; smaller physical size, lower power consumption, reduced thermal footprint and less costly. The BlackBox unit also has the advantage of being USB powered thus removing the need for an additional power supply.
System Case
Ever since seeing a NeXT workstation in the mid 1980's, I've always thought that cube shaped computers were cool. It just so happens that a cube is also the ideal shape to house four motherboards.
Cooling
Four motherboards are arranged in a star configuration around a central cooling duct.
The machines power supplies are located at the bottom of the system. Four 60mm 25cfm fans draw air from an opening in the lower-front of the cube, up the central column and into the case. The air is then drawn down over the motherboards, through the power supplies and out through a vent at the rear of the system.
Materials
Both the chassis and cover panels are made from standard industrial grade (1050A) aluminium. Apart from its relatively high cost there are almost no disadvantages to using aluminium. Its softness makes working with it a joy and helps to prolong the life of drill bits and saw blades. It also weighs a lot less than steel, it doesn't corrode (well not really), and it's a good absorber of heat and sound.
The chassis is built entirely from 20mm angle, held together with rivets. I had originally planned to MIG weld the joints, which would have looked neater, but unfortunately my welding rig wasn't quite up to the job (no AC).
The five visible cover panels (i.e. the top and sides) are made from 3mm thick sheet. The reason for choosing such thick sheet was sound absorption - and it certainly seems to have done the trick. The base plate is 1mm thick sheet with a rubber foot in each corner. The cover panels are held in place by countersunk stainless steel M5 machine screws, which are screwed into captive bolts attached to the chassis.
The power indicator lights are 3mm flat-nose red LED's, and the smart stainless steel power button was purchased from RS Components.
Paint
The chassis and cover panels are primed with three coats of etching primer, followed by four coats of colour. The top panel was left unfinished to enable items to be placed on the machine without fear of scratching the paint. The inspiration for the colour scheme came from this...
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