My early LX150 miner prototypes had a 60A switcher for vccint for 8 chips -> 7.5A each... and that later turned out to be not enough.
So, how come the German guy (Stefan) of ZTEX gets by with a [very compact] 8 Amp converter for VCCINT?
His dynamic clocking now achieves > 200 MH/s on a -3 device.
Impressive.
(Even more impressive considering the fact that he has less than half of the Xilinx-mandated amount of bypass capacitors surrounding the Spartan-6.)
Btw, one thing that made me go WTF when looking at interior pics of copacobana a few years ago... a single massive AC->1.2V converter for vccint and really heavy cables + busbars to route it around...
Here's a picture:
http://www.copacobana.org/photos/photo_b4.jpgWell, 7.5A/core was ok for a 192-205MHz 122-round 2-stage-per-round pipeline design. Just my later designs needed more power.
Also, unless I misremember, he uses ultra-low-esl 0306 caps for vccint, xilinx recommended #s are for caps with ESL values similar to 0402s... so... prolly fine.
Yep, that's the picture... Still don't get why on earth they did it that way. A AC->12V PSU and half a dozen or so point-of-load converters would've saved a whole lot of copper (and prevent accidentally welding holes in your chassis...)
