I think I've figured out something for getting back into GPU mining without spending too much. About $375 at Newegg for the following:
- Biostar Racing Z170GT7 LGA1151 motherboard ($135 for open box)
- Intel Celeron G3920 ($48)
- 8 GB DDR4-2133 RAM ($60)
- 128 GB SATA M.2 SSD ($55)
- full-tower case ($79...make sure it has room for 8 slots, not 7)
I have power supplies sitting idle from previous Bitcoin mining efforts (Antminer S1s are only worthwhile as space heaters now
), so I'll slap one of those in and call it good. The motherboard has four slots suitable for holding GPUs (16x physical; one wired 16x, one wired 8x, two wired 4x), spaced appropriately so you can actually fit four GPUs without risers. M.2 SSDs are bootable into Windows as well as Linux and don't require any extra cables from the motherboard or power supply to connect to it. (A USB flashstick would be cheaper, but is slower and only bootable into Linux). With this, I'd have space for four GPUs that's protected from having things smash into it (as with an open-frame setup), and without the issues that PCIe risers.
As for GPUs, it looks like RX470s and RX480s are unobtainium right now, as are the RX570s and RX580s that are supposed to replace them. I have a 4GB RX460 I can pull out of my primary desktop, and it looks like I can buy more at a not-too-insane price. They'll only do 12 MH/s each when mining Ethereum, but I figure I can run them for a while and replace them with something more powerful once they become available again.
Edit: On second thought, four RX460s (if I had them) would only add up to 44-48 MH/s in one box. A bit more digging indicates that a GeForce (!) 1070 ought to be good for 30 MH/s at 130 W or less (some are saying 90 W). I ran the numbers on one, and on the Radeon RX 570 and 580 at current prices, and it looks like the nVidia card wins this round. Found a used one on eBay for $375; CoinWarz says it should pay for itself in less than two months.
