I found two people who measured latencies, one a PCIe parallel port and the othe... | Hacker News

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		userbinator on April 10, 2020 \| parent \| context \| favorite \| on: PC-XT Emulator on a ESP8266 (2018) I found two people who measured latencies, one a PCIe parallel port and the other USB 3.0: https://stackoverflow.com/questions/41987430/what-is-the-low... https://stackoverflow.com/questions/13831008/what-is-the-min... PCIe parallel port: 4-8us USB 3.0: 30us I believe a regular PCI or even ISA parallel port can be below 1us. Those are "real" buses, unlike USB and PCIe which are more similar to packet-switched networks.

FPGAhacker on April 10, 2020 | [–]

I don’t know about ISA, but pci (not e) can easily be under 1us. It would be an odd design to have even that much latency.

As measured on the bus.

eqvinox on April 10, 2020 | [–]

Theoretical one-way latency on PCIe 3.0 ×1 for a 256-byte packet is < 0.5µs. A single register write should be < 0.1µs.

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