Re: 6551 driver questions

From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2003-08-23 19:56:54

On Sat, Aug 23, 2003 at 10:02:29AM -0700, Cameron Kaiser wrote:
> If you're looking for opinions, I think that would be overly limiting. With
> devices like a UDS-10, 57.6k through a T232 is the only way to fly (I use a
> hacked version of SwiftLib in HyperLink 2.5/2.5a and 2.5e (in development)
> myself).

Assuming that you didn't add interrupt driven sends: One reason why higher
baud rates give so much better results is that the Swiftlib send routine uses
busy waiting, which is a performance killer. Increasing the baud rate will
decrease the time spent with busy waiting, so your program will not only
transmit the data faster, but will also waste less cycles waiting until the
next byte has been transmitted.

What this means is that an interrupt driven send routine will increase
performance even with lower baud rates, because it leaves more cycles for the
main software for processing the data. The effect does of course depend on the
characteristics of the data: Programms sending lots of data (a web server for
example) will get much better performance, while programs just sending one
byte every few milliseconds won't notice a difference.

Regards


        Uz


-- 
Ullrich von Bassewitz                                  uz@musoftware.de

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