Bus lines on 800 motherboard

[gs80065xe]

When I had my 800 apart last month, I noticed what looks like bus lines on the back of the motherboard. They're concealed when in the case. What purpose do they serve?

[_The Doctor__]

it's exactly that, but was also used in testing during manufacture at one point. It was used not only for that testing but in some industrial applications.

[+DrVenkman]

49 minutes ago, gs80065xe said:

When I had my 800 apart last month, I noticed what looks like bus lines on the back of the motherboard. They're concealed when in the case. What purpose do they serve?

Everything I've seen says they were factory-testing the mainboards before the systems were assembled and packed into cases. I think I've seen pics of the test rig used on the production line but I don't recall for certain.