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

[Craig A. Berry]

On 11/5/21 1:46 AM, David Jones wrote:
> On Thursday, November 4, 2021 at 8:54:37 PM UTC-4, Lawrence D’Oliveiro wrote:
>> 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.

> That's a PC menatility, VAXes were timesharing systems with many
> concurrent users. C was a second class language in the VAX/VMS world,
> too, so the API wasn't designed to cater the patterns of the C RTL.
> Threads didn't exist, your server process handling many PTYs was
> state driven by ASTs delivered by the terminal driver.

And I remember lots of complaints from people who had to slow down their
typing so the VAX could catch up.