Yep.
Thick board for passive backplane application in something that went into
a phone exchange. This was from the days when buses were parallel, so
there were lots of traces between the press fit connectors. It needed a
lot of planes to keep the crosstalk down. I don't recall the exact
stackup but it was pretty much a regular board with normal thickness Cu
and prepreg, just more layers.
The thick board also helped with mechanical stability.
I don't see things like that these days. PC motherboard costs have
forced buses to be serial so it's now possible to move many Gb/s around
with only a modest number of PCB layers.
Regards,
Allan
You've obviously not seen a modern VME or Compact PCI chassis with
modern connector technology.
PCB backplanes are at 0.090" and even 0.120" or possibly even more
Mainly for rigidity since huge cards are inserted into dense connectors
(far more dense than in telco days) against them on both sides (front of
chassis and back of chassis)
Telco was 40 or 80 pins per connector, max... on a good day.
These are like 250+ pins per connector with two per card plus power
sections.
Motherboards were not "forced" to be serial, and it never had anything
to do with "costs" either.
Hard drives and their interface technology is from THEIR industry, and
THEN the PC Motherboard makers follow suit.
SAS get placed on a motherboard because SAS drives exist, not because
MOBO makers wanted to have lower costs.
Stop making shit up, boy.