🚀 go-pugleaf

On Wed, 15 Dec 1993 KSCALES@DELPHI.COM wrote:

> Actually, I generally suggest modifying /dd to maxcount=2048, and keeping /h0
> at 65535.  This allows using the higher maxcount for occasions when you
> really want every bit of speed, as when running flickers.

        Have the cake and eat it too.  Good idea.

> Yes, there is a sacrifice in speed, but drt500 doesn't come close to
> giving a meaningful reflection of the actual significance.

        Your right, of course.  What benchmark does?

> Some more meaningful speed comparisons might be:
>                                                   2048        65535
>   time fgrep zebr /dd/sys/.ispell/words           6 sec       5 sec
 ...
>   run ispell on a file; first error display       6.3 sec     5.8 sec
 ...
>   flicker iclrun.fli (1346134 char; til display)  5.2 sec     2.2 sec
>
> The last two were timed by hand, so contain "human response time" errors.

        I could live with that...

> Fact of the matter is, though, that a maxcount of 65535 is just plain and
> simple, bad "engineering practice" for multitasking with the MM/1 system
> architecture.  The DMA implementation just doesn't lend itself to that
> setup.  With a fast hard drive (e.g., Quantum), and maxcount=65535, if
> you truly have a transfer rate of 1.7 MB/s, you are effectively telling
> the hard drive "you can dominate the bus for the next 65535/1700000 second."
> This would be somewhat analogous to masking interrupts on the CoCo for
> about 0.038 second.

        OK.  I never knew what maxcount actually meant.  Alas, I am still
waiting the arrival of my manuals.

/* Blair Leduc       | Computer Engineering                           */
/* b.leduc@ieee.org  | McMaster University, Hamilton, Ontario, Canada */
/*                                                                    */
/*    ... Scotty... Hurry, beam me up before \^**@~~ NO CARRIER       */