-=> Quoting Bob Juge to Frank Sexton <=-
 BJ> V.90 STANDARD IMPLICATIONS
 BJ> [Image]   Broadly, once the two modems have established that
 BJ> they are V.90 modems and can do this trick, the
 BJ> client modem uploads a Digital Impairment Learning Descriptor
 BJ> (DILD). This basically tells the server modem what type of
 BJ> test tone to transmit over the network. The server modem
 BJ> dutifully transmits the tone, and the client modem compares
 BJ> the received tone to its internal reference tone. The client
 BJ> modem uses this comparison to calculate the best data point
 BJ> constellation to use and notifies the server precisely what
 BJ> constellation configuration to use in transmitting data
 BJ> downstream. The upstream link is still the 33.6 Kbps V.34 at
 BJ> best.
 BJ> [Image]   V.PCM describes how to upload the DILD, what to
 BJ> respond with, and how to communicate the
 BJ> constellation. The magic lies in the client modem calculating
 BJ> what constellation to use for any given set of digital network
 BJ> conditions. This is NOT specified at all in V.90 and will vary
 BJ> entirely between US Robotics, Rockwell Semiconductor Systems,
 BJ> or Lucent Technologies.
 BJ> The result is that we will have interoperable modems compliant
 BJ> with the V.90 specification and able to talk to each other.
 BJ> But it appears that large disparities in achievable connection
 BJ> speeds will depend on which client modem you are using, and
 BJ> which server modem you connect to. Our testing would indicate
 BJ> these disparities may be enormous - far beyond anything we've
 BJ> seen with previous modem standards. In the previous round of
 BJ> V.34, the Rockwell chipset was ubiquitous and modem
 BJ> performance was fairly level across the universe of available
 BJ> modems. V.34 was basically V.34. In the coming world of V.90,
 BJ> we would expect to see an almost implausible range of
 BJ> operating performance from modems all purporting to be V.90
 BJ> compatible. We'll have a standard, but it won't be very
 BJ> standard with regard to performance.
 BJ> This part of the article's findings has NOT been disputed.
That doesn't make it true, or accurate, or both.  It's just one author's
prediction.  So far, with Zoom DualMode in V90, there's been very few,
if any, interop difficulties with formerly X2-now-V90 servers.
But there's just too few ISPs yet with a full rollout to be able to be
sure.  And Boardwatch's article, having already been roundly condemmed
by both sides regarding its silly "X2 is better than K56flex" claims,
cannot be any the more sure either
Now, you've got an I-Modem setup there which presumably has got at least
V90 beta code in it.  So what's your experience?  That'd be a whole lot
more useful than re-quoting the already tarnished...
"Bellsouth.net, the ISP arm of the Bellsouth telephone company,
 has announced their exclusive support for the K56Flex protocol,
 over the x2 protocol.
"Bellsouth.net serves the Southeastern US with dial-up connections
 in about 50 cities.  All dial-up lines will be converted to new
 K56Flex modems by the end of the first quarter of 1998, and some
 areas have already been upgraded with the new modems.
"A list of cities and dates for K56Flex activation can be found
 on the following URL:  www.bellsouth.net/products/56k
"The conversion process is not expected to be troublesome; new Cisco
 Systems K56Flex modems are simply replacing the existing Cisco 33.6
 modems.
"The ease of conversion, as well as better peformance from K56Flex vs.
 x2 during trials, were cited as reasons for the Bellsouth.net decision
 to go with K56Flex.
Obviously BoardWatch knows far more about lines than hi-techies at
Bellsouth.  Wonder who's gonna tell 'em?
rgdZ :)
Richard
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