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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all. Seems that the Acer Aspire One motherboards (the AOA150 mainly) can be easily used as barebones mini PCs similar to the Beagleboard, but for not much more cost.
Plan is to fit eight of these boards into a modified Shuttle case, with the internal power supply a 19V 20A SMPS and internal screen driven off a multiplexer so it can display data from any one of the machines on command, for a total of sixteen virtual cores at 1.66 GHz., hence "Hydra" the multiheaded beast.
Typical prices I am seeing on Ebay are around £20 for "bad" boards and £60-£80 for known good ones.
A few of these bad/faulty motherboards fail due to the power connector warping due to overheating and shorting internally, even if you replace this connector chances are the short will still be present.
So I've now taken to removing the damaged board section, sanding down to remove any sharp edges and burrs, then wiring from the fuse area having first replaced if it is blown to +19V and Gnd.
Only needs to be done if the power connector is shorted however, otherwise just removing it will suffice.
An additional problem is that the "ports" board often has damage to the power switch, so by shorting the end two pins on the PC end as shown it then powers up fine. as the amplifier is internal to the motherboard this connector is only really needed for the power, USB, card reader and audio out.
EDIT:- An interesting fault I found near the VGA connector is that the smd electrolytic lifts at one end, normally not taking the track with it. Resoldering usually fixes the glitchy graphics.
The other problem is BIOS related, and for £9.99 you can get a new programmed chip off Ebay or just reprogram the old one if you don't mind repeating the procedure every few months.
Cooling could be interesting, but as these boards have their own internal fans a simple piece of aluminium with heatsink elastomer to the relevant chips and HDD if present should do the trick.
so far I have two known good boards plus my current noteboook; one seems to want to go into the BIOS every time you switch it on without the hard disk though...
EDIT: plus three more faulty boards turned up, and had to swap the bios chip to my laptop from one working, two of three "bad" boards work after reflashing and I have one unresponsive to reflashing... so if anyone has a source of blank 1MB Winbond serial chips let me know. Total expenditure so far:- £59 Have another SSD board on order which is easily modified, so need another three and a BIOS chip.
Obviously if watercooled this setup would be "fun" to overclock, as these chips can take 1.8GHz without even noticing and can be pushed well over 2 GHz if you keep them cool enough.
Unfortunately it looks like you need to boot from USB as neither of the internal card ports will boot. this appears to be a limitation of these but its only really an issue if the setup does not have a drive for each "node".
the fix i have devised for this is to boot using the camera USB lines, requiring a cheap pendrive for each "node" or some method of switching a single drive to eight boards. Can you say "quad bilateral 4016 switch" ?
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi, Update to thread, including recent data.
Have modified a test board to confirm that they work fine with a simple power switch soldered to the point shown (helpfully Acer are hot on test pads )
Thanks to aceronespares on ebay, as this at least confirms the BIOS chips are often the problem and if reflash doesen't last then replacement is relatively simplez.
Have recovered all but one A1 motherboard, for some reason the flash-only one is totally fried. Replaced BIOS chip and repaired a damaged track near the chipset going to a small diode, but still nothing.
I did notice that the Vcore seems to be abnormally low at 0.88V instead of 1.27 on my test board. is this likely to cause it not to boot? all other voltages seem to be within spec so if I can locate the Vcore regulator I might be able to fix the problem.
-A
"Bother" said Pooh, as he realised his solder flux was two years past its use-by date...
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Hydra
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