Bueno pues despues de hacer muchas pruebas y de leer en muchos foros, parece que el tema se va aclarando y quizas enredando, he sacado del foro de xboxhacker este post que me ha arecido interesante:
Xbox (or better evox dashboard?!?!?) TCP/IP stack implementation is $#!tty, but after some test, i think that problems of slow is not there.
Xbox uses a 1440 bytes of MTU, windows usually 1500
Xbox uses a TCP windows size of 16800 bytes. windows uses 64240 bytes
I've tried to set my ethernet card to the same value as xbox ethernet card, so 1440 MTU and 16800 windows size, hoping that upload speed will result = download speed.
No appreciable result.
The only interesting point is changing xbox HD:
Xbox original seagate hd: up 2mb/s dow 9mb/s 100 half duplex
Xbox with IBM 7200 30g: up 4,5mb/s down 9mb/sec half duplex
Ok, minimizing the FTP client buffer size speeded up my upload fraom 1mb/sec to 2mb/sec with original xbox drive, but with the new fastest drive, no appreciable speed increase.
At this point, i think that problems are in the FTP server or into FATX file system that is maybe fast in reading but slow in writing, am i wrong?. To know if problem is in FATX, I'll try to copy from DVD to original HD and to a faster HD, if speeds are the same, the only problem is in evoxdash FTP server.
Because evox ftp server oesnt support passive mode, if you dont force active mode in flashfxp, it will try passive first, then active for every file. So i suggest to remove flag to "use passive mode" in case of multiple small files.
Para los que querais ver el hilo completo este es el link
http://www.xboxhacker.net/forums/index.php?act=ST&f=6&t=4938&st=15
Despues de esto creo que es la combinacion del evox+cliente ftp+tarjeta de red+HD+sistema operativo. lo que nos da el cocktail final de velocidades que son tan dispares entre si. Lo que todavia no he podido probar en mi caso es cambiar los valores de mi tarjeta de red (MTU) pues no encuentro como.
Espero que esto ayude un poco.
Salu2