Standard Sli
thats 1-1 pin all going to same pin numbers 2-2 and so on
and it doesn't matter if you install the bridge in the front or back sli in 2 way
now saying that - some are data - some are hardware signal lines - ack/nack/control lines
you need 8 or 16 for data - that would leave 8pins for other uses - power gnd and control/flow
we know one is used for lighting a sli bridge ie 5v otherwise lit bridge would change with activity
process lines could indicate send /receive data - or indicate data or address location
you could have 8 data and 8 address - but im assuming you use a control lines to specific data/address and use 16bits for both
since i don't know all the particular pinouts it's moot
in 3 way you have double bandwidth but 3 cards
assume a hookup like this
1-------->2------>3 - and use 2 pins to indicate what card data sent to or address or command
1<--------2<------3 that goes for both directions
or option 2 you use a control line to indicate flow
and do only one flow direction - and flip when you want to do data/info the other way
4 way
however comes the problem with control.... sli works master and slave and slavemaster 2 and slave 3
where slave2 is master over slave 3 and master can control slave 2
so i bridge used for control
down to double bandwidth/ 4 - control overhead
look at this from bandwidth perspective
using 1 bridge for 2 cards - normal
if it was possible using 1 bridge for 3 - 1/2 bandwidth...... for 4 cards - 1/4 bandwidth
using 2 bridges for 2 cards - double bandwidth - for 3 cards double/3 - overhead (close to normal bandwidth).... for 4 cards double/4 - overhead less than normal bandwidth
and why Sli has problems scaling
you lose bandwidth as you add cards
the HB bridge would not need the extra control lines - this you can hang one high ie 5v and one low(gnd) to indicate to the cards and drivers a hb bridge
on the other cards the bridge would hang/fail the SLI
if you use regular bridges on 1080 would work normally