PCI-e is just a pain in the ass for mining. You need gold finger controlled impedance PCBs, a
flash PROM to configure the FPGA before the PC BIOS scans the bus, much more complex
interface logic in the FPGA, more complex SW, and possibly a $$$$ high speed scope if
something goes wrong, just to provide insane amounts of bandwidth you don't even need.
Plus, putting 16 $150 BGAs onto a single giant PCB is a bad idea. 1 out of every 20-30 boards will have
a critical defect under 1 of the FPGAs, costing you either $2400 to scrap the board, or a bunch of time and
money to try to remove/reball/repair it. There's a good manufacturability reason to use only 1-2 FPGAs per PCB -
if something goes very wrong you're out $300, not $2000.
-rph
totally agree with you.
What the hell, with a high speed CPLD you can probably bitbang pcie, last time I checked those cost around $5.
Some of those can interface with almost and logic level & impendace.
The thing what concerns me is: Why use a PC anyway? We could possibly implement the mining software on a cheap ARM, pair it with a ethernet MAC ic and be done with it.
on my design, the upper computer only need send and receive mining datas, so a hacked router is enough.
What the hell, with a high speed CPLD you can probably bitbang pcie, last time I checked those cost around $5.
Some of those can interface with almost and logic level & impendace.
The thing what concerns me is: Why use a PC anyway? We could possibly implement the mining software on a cheap ARM, pair it with a ethernet MAC ic and be done with it.
Scalability. If you wanted to build a 20G/s cluster are you going to have 100 cases, 100 boards, 100 ARM processors, 100 ethernet ports, 100 wallwart power-supplies?
no case, 100 boards, 1 arm processor, 1 Ethernet ports, 2~3KW 12V power-supplies is ok.
