Xilinx ISE doesn't support schematic entry?
I'm glad I use Altera's Quartus II that does
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To the OP, since it's on dedicated hardware you might find it very difficult to program it, and when or if you do, you might not have access to pins that you can designate. A dev board would have been easier than some bitcoin miner already configured to do what it does. Not impossible since it's probably flashable but without documentation it will be almost imposible.
It would be like using a Rigol Scope as an FPGA dev board, not worth it, but if you want to share more info/pictures of the device maybe someone can point you to where to get the documentation for it.
BTW kidding about Xilinx not having an schematic editor, because of course it does.
Another thing is that you can convert Verilog/VHDL modules to schematic and use them as well provided you know what it does within the module, but it will expose the input/ouputs/inouts & buffers in schematic form. Well at least Quartus can, never used ISE.
Edit: for example this thing:
http://fpgamining.com/products/x6500-rev3even if you could program it via JTAG what could it do if you don't have access to any pins to look on what is doing?
Edit2: oh and BTW you are going to need to do a boundary scan to see what device is in there or pull the heatsinks because you will need to know the device in order to program it.