maximum ethernet speed

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originally posted by revolt@Oct 1 2005, 07:09 AM

i took a look at a 1000 mbit mac ip from morethanip. they use a 4 bit mii interface @ 25 mhz to transfer the data to the phy. so the interface has a limit from 12.5 mbyte/s. i think gigabit ethernet is not fast enough.

kind regards

revolt

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that would cap the datarate at 100 mbit exactly, so there wouldnt be a point in using a Gbit lan mac

by the way, when you want to reach 600 mbit (or even 400) then the receiving end station will be a problem, since 600 mbit is 75 mb/s, there are very few non server system that can sustain this kind of speed, so even if you could get this with a nios or orther FPGA system, the receiving end will have one hell of a time taking the data in (most normal HDD&#39;s cant do sustained writes over 60 mb/s)

by the way, revolt, you said you did the checksum in HW, i asume this is a function normally done by the lwip? like CRC?

Hi All,

the checksum that LwIP is doing, can also be done by HW. How can I make that happen?! What do I have to change in order to let it be checked by hardware?

Danny

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that would cap the datarate at 100 mbit exactly, so there wouldnt be a point in using a Gbit lan mac[/b]

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I searched a litte more and found a PHY IC from National (DP83865) that have a 8 bit wide interface (GMII) @25MHz. Then you have 200Mbit.

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by the way, revolt, you said you did the checksum in HW, i asume this is a function normally done by the lwip? like CRC?[/b]

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The checksum calculation for the UDP packets is done by HW. Normally it is calculated by the lwip stack.

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originally posted by revolt@Oct 16 2005, 11:34 AM

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by the way, revolt, you said you did the checksum in hw, i asume this is a function normally done by the lwip? like crc?

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The checksum calculation for the UDP packets is done by HW. Normally it is calculated by the lwip stack.

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[/b]

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i see, i asume you do this with a custom instruction in the nios?, or did you put a discrete block of vhdl between the nios and mac/phy? and do you know if this can also be done with TCP packets? i asume so..

There is a discrete block of vhdl between the nios and mac/phy. In my application I only use UDP packets, so I never tested it with TCP packets.

regards

Revolt

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originally posted by revolt@Oct 18 2005, 03:22 PM

there is a discrete block of vhdl between the nios and mac/phy. in my application i only use udp packets, so i never tested it with tcp packets.

regards

revolt

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i see, we are using strictly TCP right now

ive been working on the LWIP stack code, and to my horror simple tests about the amount of clock cycles needed for CRC seemed to indicate a cpu usage of 99.6% http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/blink.gif so needless to say i am gonna try and accelerate that process somehow, because this is plain ridiculous...