Is ULTRIX-11 really slow?

[Dan Ts'o]

In article <> martillo at mit-athena.UUCP (Joaquim Martillo) writes:
>Console I/O is much less efficient the ordinary terminal I/O.
>If your friend only has a console on his pdp11, he will find I/O
>very slow.

	It is not clear what you mean...

	If you mean that output generated from the kernel version of
printf() in older UNIX's usually in the form of error messages from the
kernel printed on the console is very slow and efficient, then you're
right. The internal version of printf() does not use interrupts and
character buffers, but tight loops on console output which pretty much
suspends the rest of UNIX. This "feature" has been fixed in some UNIX's.
However, it is not the normal mode of "console I/O" and could not be
considered a reason why ULTRIX-11 is slow.

	If you mean that console I/O is slow because on PDP-11's it is
usually done to DL-11 serial interfaces which have no silo nor DMA
capability, in contrast to terminals on DH-11's and DMF-11's. This situation
is also true but I think negligible in most cases. We run 11/23's and
11/73's on DL-11 interfaces and aren't bothered too much by the performance
of the DL-11's. But if you're doing heavy I/O on the console line, e.g.
graphics or UUCP, then it might be a problem.

	If you mean that older UNIX's don't buffer stdout on terminals,
that's right but valid for all serial lines. This problem is much more of
a performance factor than the DL-11 problem.