How difficult would be to daisy chain the USB, and power?
USB can't easily be daisy chained (would require a 2-port USB hub on each board, and you may only chain something like 6 hubs total (including hubs that are possibly integrated in the PC).
@TheSeven:
I'm glad you noticed the FPGA 0 / 1 invalid thing too. I didn't think much of it at first but I think it might be more hardware related then anything (I experienced the same issue of FPGA 1 generating more invalids then FPGA 0, which usually had 0% invalids). However having said that I'm at about 0.2% invalids on FPGA 1 and 0 % on FPGA 0 after 4 days of 24/7 mining so I'm not really too concerned about it at the moment.
BTW with regards to the plastic surface on the FPGA; do you think the anodized aluminum will do as good of a job as a full copper heatsink? I think a copper heatsink + good thermal compound (and/or epoxy) + active cooling should do the trick of eliminating overheating as a source of mh/s degradation.
Cheers,
nbtcminer
Hm, very interesting. The results I got from MPBM show a slight bias towards FPGA0, fizzisist's x6500-miner results show a bias towards FPGA1. Might after all be related to how x6500-miner deals with the FPGA alternatingly while MPBM manages them in parallel or something like that.
An aluminum heatsink certainly can't keep up with a copper one, but I don't think it really matters much whether the heatsink is like 2°C cooler if the temperature difference between the die and heatsink is like 20°C because of the FPGA's nasty package. So yes, it might improve things, but it might just not be worth it, some airflow around the ground plane of the PCB might have a bigger effect. (All guesstimations, feel free to prove me wrong
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the x6500 miner software seems to have some trouble with p2pool, after some hours of work with avarage 5% rejected 0 stale shares the miner just pulls blocks but doesnt provide any shares, have to restart the software to make it work again. does someone have this aswell with p2pool ?
The way the X6500 communicates with the controlling PC works well for regular bitcoin mining, but introduces some latency (a couple of milliseconds) that hurt P2Pool a lot at its very high block rate. So you should expect degraded efficiency when using an X6500 with P2Pool. This might be addressed in a future board revision. (The miner software might also have an impact, but it isn't all that big.)
Should work with MPBM and possibly also with X6500-miner if libd2xx is available for ARM platforms and the board can handle it performance-wise.
I'd say that with MPBM up to 4 boards should work well, if you have more you might run into performance issues.
