On Nov 29, 2013, at 9:47 PM, Jonathan Morton wrote:

> 
> On 30 Nov, 2013, at 7:39 am, Gregg Eshelman wrote:
> 
>> That causes problems with many 10/100/1000 megabit switches and routers 
>> which rely on media type identification instead of sussing it out from the 
>> data transmission. No media type ID, no connection for you!
> 
> I thought the spec was to default to 10baseT half-duplex if auto-negotiation 
> was not present at either end.  That works well enough with a 3c509B in a PC, 
> for example, and it also works just fine with the adapted MACE AAUI in my 
> 840AV and 8100/80, and the 8390-based NuBus card in my IIcx, when I attach 
> those to a 10/100 switch.
> 
> The 3c509B was one of the first cards to support 10baseT *full* duplex, but 
> did not support auto-negotiation and therefore requires a managed switch 
> (with the port forced to the correct mode) to make use of that feature.  
> However, in half-duplex mode it works just fine as-is.

The problem isn't really with the various Ethernet cards, the problem is with 
trying to auto-negotiate the speed with a card that was never designed to 
negotiate speed.  The auto-negotiation process is making certain assumptions 
about the device on the other end that aren't true in some cases.  And so 
auto-negotiation doesn't always work.  Why it couldn't have been designed to 
fallback to 10BaseT, I don't know.

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