It's not true that pcb has a "fundamental" limit of 8 layers. There are 8 copper layers. There are TWO silkscreen layers IN ADDITIONto the 8 COPPER LAYERS. You can draw lines, arcs and polygons on the silk layers. It's fairly straightforward to add several non-copper layers for things like keep-outs, outline, or the mask layers. The hard part is implementing the functionality associated with those layers. It's more of a "fundamental" limit to go beyond 8 copper layers but then nobody has ever, to my knowledge, built an 8 layer board with pcb. I know of a few 6 layer boards, many 4 layer boards, tons of double-sided boards and few single-sided boards but nothing beyond 6 layers. It is rare indeed that more than 8 copper layers are required. Usually when 10 and 12 layer boards are made it is because the designers are lazy.
The Pentium processor chip has only 7 wiring layers; it must be of "medium to low" complexity! Eight copper layers is not presently a serious limitation to users; Even so, storing the PIP/Thermal flags separately from the main "flag" variable would quickly allow expansion to 16 copper layers, but it'll be a pain to handle the grouping dialog, on/off and layer naming for them. harry ----- Original Message ----- From: "DJ Delorie" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, January 05, 2005 1:17 PM Subject: Re: gEDA-user: PCB suggestion > <snip> > > PCB at the moment has a fundamental limit of 8 layers, and assumes all > eight layers are copper. The rest of the layers are deduced from > those. Changing its internals to have a virtually unlimited number of > layers, and explicit layers for such annotations, is a technical > problem, not an interface problem.
