Can antone tell me how many bitfury's can be chained?
Ive seen the proven 16 bitfury design. metabank has multiple chains.
Nowhere is listed how many you can put on one chain.
No there is no such information and there are no limits from the chips themselves, but ...
There are 2 types of limiting factors involved:
[1] RPi (or other device) processing power, which applies to both single and multiple chains, but also on software.
[2] each chip in the chain adds some delay, which results in lower SPI speed required in order to successfully communicate with the last chip in the chain, then at some point your SPI communication will be too slow to walk all the chips in the chain in time before they need new work.
BSB has 4 boards of 16 chips each in a chain, so 64 chips are proven to work. I have read somewhere about 100 chips working in a chain and about 400, but not sure if in a single chain or just on the same RPi.
Going for more than 150-200 in a chain is unreasonable because of [2] and more than 350-450 total because of [1] which is close to those 100 and 400 numbers above