[BBF Standards] systemic limitation of biobricks for combinatorial logic?

[J C]

Hi all,
I have been reading about biobricks for some time,
I am a computer engineer.

For combinatorial logic, it seems the limitation of biobricks
is the system-wide visibility of all gate outputs, is this correct?
In circuits with multiple gates, each gate must employ a unique
 input signal and output signal, otherwise the multiple outputs
will conflict with the inputs.

How is this being addressed other than by finding unique
signals to feed to each gate?

This is not a scalable solution for larger circuits, i.e. adders
or latches (RAM storage for more than 1 bit).

Can this be solved by using single cells for each circuit, then
somehow providing inter-cell communication?
(Also seems quite difficult, correct?)

There was a similar comment on this recently, though I didn't
see any solution discussion?
http://biobricks.org/pipermail/standards_biobricks.org/2008-February/000034.html
"The lack of physical separation of signals, as is the case in
microelectronics, could be one of the biggest limitations to the
standardized bioparts concept. "


The idea offered in that thread,
"Actually this could lead to a design process where you operate e.g. on a
system level and design your nice circuit, but depending on the circuit the
design computer programme chooses one of different devices (and finally
parts) that interact in the way you like."

This is actually quite impossible for multi-gate designs.  A multi-bit adder
or memory storage would require far too much complexity.  The components
(i.e. "transistors") need to have completely compatible outputs so that
any output can connect to any input.  Otherwise they are not "generic parts".
Similar issues led to much complexity in the early days of semiconductor
fab.

--
Cheers!