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:
~$25,000
50 Ghash/s
2500 watts
![Huh](https://bitcointalk.org/Smileys/default/huh.gif)
unknown rack spaces
I suppose this serves to illustrate how badly FPGAs have the potential to
kick whomp 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
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
). 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.
![Huh](https://bitcointalk.org/Smileys/default/huh.gif)
EDIT: minor spelling corrections.