[Info-vax] DECnet Phase IV broken after VSI update

[Lawrence D’Oliveiro]

On Thursday, November 4, 2021 at 5:54:21 PM UTC+13, osuv... at gmail.com wrote:
> Most of PTD$ code runs in kernel mode with some at elevated IPL.

So does a device driver. Why do the PTD functions have to be a separate layer from the device driver? Particularly a separate, caller-visible layer that breaks the normal driver QIO abstraction?

> PTD$READ/WRITE queue request packets directly to FTDRIVER, 
> skipping some of the overhead of $QIO processing.

Remember, these are terminals we are talking about -- devices geared to the limits of human I/O bandwidth. Any “overheads” associated with I/O processing would be insignificant compared to the time it takes for a human to type input or read output.