Item — HN Reader

> I’m pretty sure PCIe isn’t 5V. Probably more like 1.8V, so already starting with a much smaller range.

I'm fairly sure the most modern PCIe standards are all the way down to 1.2V. Prior to 1.2V it was 1.5V, 1.8V, 2.5V, and back in the days of the original spec it was 3.3V. I can't remember exactly what versions speced what voltages.

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Modern PCIe uses a complicated transceiver design that does pre-emphasis/de-emphasis on the signal. The actual signal swing is differential, and on the order of +/-200mV (with a relatively low voltage common mode, on the order of 300mV) after all the attenuation.

What the actual digital IO voltage that the chip that does PCIe driver is driven from is almost unrelated.