Re: gEDA-user: transition of pcb internal units to metric (SI, mm)

[Markus Hitter <mah@xxxxxxxxxxx>]

Am 07.02.2011 um 19:37 schrieb Colin D Bennett:

> This has been discussed on the list before and the proper answer is to
> use 64-bit integers representing length in nanometers.

Isn't a nanometer pretty big when doing chip design? Others might  
have more/any experience in this area.

> I believe
> the solution is to make the standard internal representation a 64-bit
> integers but provide a compile-time configuration option to use
> 32-bit integer representation

Now _that's_ asking for trouble. Essentially, you have to code all  
the maths twice, and in a compatible manner. You have to compile  
twice to run tests - or to continue to develop in pure 32-bit.

Seeing about any serious desktop or server CPU has a 64-bit maths  
unit these days, it's probably not worth this trouble.

My $0.02 suggestion would be to use picometers with 64-bit only.  
That's still +-9000 km possible board size.


Am 07.02.2011 um 19:41 schrieb DJ Delorie:

> Please don't start the discussion again;

Sorry, DJ, just trying to get PCB out of the habit to change units  
every few years.


Markus

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Dipl. Ing. (FH) Markus Hitter
http://www.jump-ing.de/







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