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Re: [avrdude-dev] avr910 speed-testing/tuning
From: |
Joerg Wunsch |
Subject: |
Re: [avrdude-dev] avr910 speed-testing/tuning |
Date: |
Wed, 10 Dec 2003 13:04:32 +0100 |
User-agent: |
Mutt/1.2.5i |
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/
Re: [avrdude-dev] avr910 speed-testing/tuning, E. Weddington, 2003/12/10