Still FPGA worry me for anything w/ a ROI beyond a year.
So I decided to run some more numbers, and found out just exactly how bad of an investment this could potentially be.
So lets assume that IF
a 7990 had 2 cores capable of 600 Mhash/s each at stock clocks, and IF
they pulled the full maximum of 375 watts for a PCI Express card (2x 8pin @ 150watts each = 300 watts, plus 75 watts from the slot), and IF
I could get all 18 slots populated and working with virtual machines or whatever technology, and IF
it cost me a conservative estimate of $25,000........
.......that would mean numbers such as the following:
21.6Ghash/s per rig
~7500 watts power draw at the plug(s) (assuming 95% efficiency, which is more common in server-grade power supplies)
6-8 U rack spaces, depending on how it was architected.
Now, if we assume for a moment that the BFL Rig Box exists and works at the numbers stated, that is as follows:
unknown rack spaces
I suppose this serves to illustrate how badly FPGAs have the potential to
BLAST the ass of video cards into next week.
Since my power is 9 cents kw/h, I decided to do an ROI calculation. For the custom monster machine with 18 video cards, ROI is slated to be ~250 days, assuming the difficulty and price remain the same (yeah right
). For the Rig box, it is 95 days. Of course, the video cards and waterblocks have known resale value, but damn.... less than 100 days. I STILL
am not sure whether I want it to be true or not.
EDIT: minor spelling corrections.