OT? Upper limits of FSB

On Jan 4, 2019, at 11:02 PM, Jeffrey S. Worley via cctalk <cctalk at classiccmp.org> wrote: Apropos of nothing, I've been confuse for some time regarding maximum clock rates for local bus. My admittedly old information, which comes from the 3rd ed. of "High Performance Computer Architecture", a course I audited, indicates a maximum speed on the order of 1ghz for very very short trace lengths. Late model computers boast multi-hundred to multi gigahertz fsb's. Am I wrong in thinking this is an aggregate of several serial lines running at 1 to 200mhz? No straight answer has presented on searches online. So here's the question. Is maximum fsb on standard, non-optical bus still limited to a maximum of a couple of hundred megahertz, or did something happen in the last decade or two that changed things dramatically? I understand, at least think I do, that these ridiculously high frequency claims would not survive capacitance issues and RFI issues. When my brother claimed a 3.2ghz bus speed for his machine I just told him that was wrong, impossible for practical purposes, that it had to be an aggregate figure, a 'Pentium rating' sort of number rather than the actual clock speed. I envision switching bus tech akin to present networking, paralleled to sidestep the limit while keeping pin and trace counts low.....? Something like the PCIe 'lane' scheme in present use? This is surmise based on my own experience. When I was current, the way out of this limitation was fiber-optics for the bus. This was used in supercomputing and allowed interconnects of longer length at ridiculous speeds. Thanks for allowing me to entertain this question. Though it is not specifically a classic computer question, it does relate to development and history. Best, Technoid Mutant (Jeff Worley)