Re: [avrdude-dev] avr910 speed-testing/tuning

[Joerg Wunsch]

As Jan-Hinnerk Reichert wrote:

> The explanation is simple: The PC's UART (TL16C550) waits 4 
> byte-lenght before it requests an interrupt, because the 
> FIFO-threshold of 8 is not reached. The remaining 0.4 byte-lengths 
> are SPI-transfer in the programmer and system/program-overhead.

The designers of UUCP already knew that request-response protocols
suck.  The designers of AVR910 apparently didn't have this 20-year old
knowledge...

> However, there is no simple solution here, since the FIFO-threshold is 
> hardcoded in the kernel.

For FreeBSD, the FIFO can be disabled per device at boot-time, using
device flag 0x02.  For FreeBSD <= 4, this is a kernel comfiguration
parameter but one that can be overridden by the loader at boot-time.
For FreeBSD 5, this is always configured in /boot/device.hints, no
recompilation required at all.

-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/