Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!sun!amdcad!brahms!ncpjmw
From: ncpjmw@brahms.amd.com (Mike Wincn)
Newsgroups: comp.dcom.lans
Subject: Re: 10baseT chip question
Message-ID: <1990Oct10.211301.26710@amd.com>
Date: 10 Oct 90 21:13:01 GMT
References: <14403@netcom.UUCP>
Sender: usenet@amd.com (NNTP Posting)
Organization: Advanced Micro Devices; Sunnyvale, CA
Lines: 40

In article <14403@netcom.UUCP> jbreeden@netcom.UUCP (John Breeden) writes:
>Rumor has it that the AMD 10BASE-T MAU chip has half size Link Integrity 
>pulses. Can anyone confirm this? Besides being non-conformant, doesn't this 
>shorten the distance below 100 meters?
>
[...]
> John Robert Breeden, 

In answer to your question:

	The TPEX (Twisted Pair Ethernet Transceiver) Link integrity pulse
is not "half size", but it is not the full amplitude permitted by the 
transmit template shown in the 10Base-T Standard.  Figure 14-10 of the
Standard allows the amplitude of the Link pulse to vary from 585mVpk to 3.1vpk,
when tested with a variety of loads that include a model of 100m of 
unshielded-twisted-pair (UTP) line.  TPEX meets the template in the 10Base-T 
Standard for all of the required load conditions, including 100m 24GA UTP, 
so it is therefore "conformant". 

	In general, if extremely poor quality cable is used, both the Link 
integrity pulses and transmitted packets can be degraded so badly that the 100m
target distance of 10Base-T cannot be achieved, though the use of poor quality 
cables is not precluded by the Standard.  TPEX works very well over the typical 
telephone cables recommended in the Standard, and certainly achieves the
100m target distance.  

	Strictly speaking, it isn't yet proper to classify a 10Base-T device
as "conformant".  For this, the IEEE have to bless a "Conformance Test
Document", which is basically a set of test procedures to enable all of the
requirements of the Standard to be examined in a predictable and repeatable
manner.  Since Ian Crayford and I were directly involved in both the 10Base-T
standard development and the design of the TPEX chip, plus will be involved
in the generation of the Conformance Test Document, you can rest assured that
current and future AMD 10Base-T networking products will be "conformant".

Mike Wincn, MTS 			Ian Crayford 
TPEX Project Leader 			Product Planning Section Manager  
Network Products Division, AMD		Network Products Division, AMD 
ncpjmw@brahms.AMD.COM			(408) 749-4017 
(408) 749-3156