21 Mar 2004 Grit   » (Journeyer)


Been chasing TCP performance problems. We're sending lots of data over a Gigabit Ethernet switch. Unfortunately TCP's timing parameters are tuned for the wide-area; it's ridiculous to wait 500ms for SYN ACK and have a minimum RTT of 200ms when the other end really is less than 1ms away. Having a 1MB transfer sometimes be 11ms and sometimes be 211 ms or 511 ms is no fun.

Fortunately we're using Linux, and we're in a situation where we can just change the constants and recompile. Or, if necessary, we can use a different transport protocol--- but TCP seems to be good enough if tuned. (It's understandable, if a little annoying, that these numbers are compile-time #defines rather than dynamically adjustable variables.)


I got a bunch of sample microcontrollers from Microchip and have been playing around with them. I wrote my own programmer (adding yet another to the hundreds out there) and have only ruined one chip so far due to getting +5V and +12V switched around...

I've using gpasm from gputils as the assembler; it's a well done open source tool.

My I2C "logic analyzer" is complete; I put a couple new pictures on my electronics page. My soldering skills have yet to noticeably improve.


I visited a couple more electronics stores in the Minneapolis area today. AEI Electronics was a little disappointing; they have a lot of audio stuff, but not many parts out and available. Even IC sockets were in the employee-only area; I prefer being able to look at what I'm getting. Plus they overcharged me for the sale items I got but didn't charge me for my resistors.

Midwest Electronics was about what I expected; they do mainly old computer stuff. I restrained myself from buying one of the stack of Sun workstations for $10. I did find a tube of 18-pin DIP sockets which didn't have a price tag, so they let me have it for free.

So it looks like ABC Electronics is the best so far--- unfortunately they're not open on weekends.

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