copper traces to nowhere on MSI desktop motherboard

to PCI bridge chip. That chip seems to be designed to connect to 2 thin serpentine copper traces, each about 2" long, that go nowhere. On this particular motherboard they're not used at all because the jumpers that normally connect to the chip (labeled SIM1 and SIM2 in the picture below) aren't installed, and neither are the header pins for the jumpers. Notice that each serpentine trace has 2 traces adjacent to it that follow it, only they're designed to not be connected to anything at either end.

pinout, but does anybody know the purpose of unconnected serpentine traces like these?

Sometimes those are used to generate very short pulses, in lieu of a chunk of coax. But hard to say without a schematic.

PCI bridge chip. That chip seems to be designed to connect to 2 thin serpentine copper traces, each about 2" long, that go nowhere. On this particular motherboard they're not used at all because the jumpers that normally connect to the chip (labeled SIM1 and SIM2 in the picture below) aren't installed, and neither are the header pins for the jumpers. Notice that each serpentine trace has 2 traces adjacent to it that follow it, only they're designed to not be connected to anything at either end.

pinout, but does anybody know the purpose of unconnected serpentine traces like these?

I would guess it's for testing the PCB controlled impedance (using a microstrip line test coupon) by way of the missing 'SIM2' header. Nothing to do with the chip.

I-E to PCI bridge chip.  That chip seems to be designed to connect to 2 t hin serpentine copper traces, each about 2" long, that go nowhere.  On th is particular motherboard they're not used at all because the jumpers that normally connect to the chip (labeled SIM1 and SIM2 in the picture below) a ren't installed, and neither are the header pins for the jumpers.  Notice that each serpentine trace has 2 traces adjacent to it that follow it, onl y they're designed to not be connected to anything at either end.

pinout, but does anybody know the purpose of unconnected serpentine traces like these?

Funny looking transformer?

Mark L. Fergerson

Bob Boblaw wrote in news:9f649128-febe-4668- snipped-for-privacy@googlegroups.com:

That looks like a nice delay line,providing you with a reflected pulse for every transmitted pulse. Now start thinking about how to use that pulse..... (oh, and make the transmitted pulse short enough to not interfere with the returning echo pulse).

More likely it is there to measure the properties of the PC board. Maybe for QC?

tm

Or a secret antenna? Big brother watching? Oh-oh ... :-)

The PCI buss is based on reflected signals.......

Maybe some kind of sanity check.

Cheers

I like to put test traces on multilayer boards, to see how close my trace impedance math, and the fab house's compliance with my stackup, are.

It's fun to do right angles and vias, and cross slits in ground/power planes, and violate HoJo's dire warnings about "return currents" and "reference planes."

But if that one above is an impedance test coupon, it's surely a weird one.

Google "quarter wave stub"

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

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