abit mobo amperages!!!

[OuTpaTienT]

Saw this on Ace's Hardware message board (http://www.aceshardware.com/board/general/) :


The 1GHz “Classic” Athlon alone requires 37 amps under continuous heavy loading. With Thunderbirds, those demands have increased: The 1.2GHz model requires a maximum current of 39A, the 1.3GHz requires 41A, the 1.4GHz 43A, and the 1.5GHz requires an unprecedented 46A! [...] Therefore ABIT has gone one step further to innovate 3-Phase Power on the KT7 and KT7-RAID for 1.3GHz+ Thunderbirds.

[This message has been edited by OuTpaTienT (edited 10-31-2000).]

[desmocat]

I just went to abit's page and was looking around when I saw the banner touting that one of their new mobo's have 3 phase power supply. It stated that the athlons were pulling around 40 AMPS under full load and the new board would be capable of handling 50 amp loads. Is it me or do these amperages seem excessive? I mean,40 amps on the tiny solder traces on a motherboard= smoke, maybe? take a visit and tell me your feelings on this.. Mp
Link: www.abit-usa.com (http://www.abit-usa.com)

edit> look about 3 articles down on the news page http://sysopt.earthweb.com/forum/wink.gif


[This message has been edited by desmocat (edited 10-31-2000).]

[This message has been edited by desmocat (edited 10-31-2000).]

[tonym]

desmocat,

The current flows in places that you can't see!

Any motherboard is a more complex structure than the outer layers of PCB etch reveal! These boards can be up to 10 etch layers thick (layers=cost, so PC mobo mfgrs. try like crazy to keep the layer stackup small!!). And very dominant in these layers are Vcc (power) and ground planes. These planes alternate every other layer (and sometimes every other two deep twoards the board center if stripline techniques are used) for impedance and signal integrity reasons.

The power/ground etch layers are flood etches -- that is they are solid layers except for the "swiss-cheese" effect that occurs from inter-plane vias and connector/IC pin keep-outs, etc., so they are very low resistance/impedance. And to increase the ampacity, planes are often connected in parallel.

As a matter of fact, the 40A Athlon board is a puny (!) current-hog in relationship to some of the boards prsently in use. Last month I finished up a network processor/switch-fabric board for a telco application that has 4 power sources and they draw 12, 30, 38 and 95A respectively! The 95A is at 1.8Vdc, and presented several design challenges. Remember, at first blush the 1.8V powr dissipation is "only" 171 Watts...no big deal. Right? Until YOU have to make it work!!! This baord ended up having 28 layers and used several power/ground planes for each power signal distribution.

So, it's not necessarily what you see...it's the hidden details that make things work!!

Hope this helps...


Tony

[desmocat]

COOL! Thanks for the insight Tony, I learned something new today.. You gave a bunch of info on board design I knew nothing about. Thanks! http://sysopt.earthweb.com/forum/smile.gif Mp

[Graham]

Nice to have an expert on 'board' http://sysopt.earthweb.com/forum/smile.gif

Ampacity ????? http://sysopt.earthweb.com/forum/smile.gif

G