Looking for Larscom CupreDSU

From: Michael Sokolov <msokolov_at_ivan.Harhan.ORG>
Date: Sun Jan 2 14:45:52 2005

Hi everyone and Happy New Year,

This is probably OT because the piece I'm looking for is not 10 y old, however,
it is an item of interest primarily to those with a passion for classic
computing and seems to be absolute unobtainium, much harder to find than
many older items.

The CupreDSU is a unit that allows one to connect a classic router of the
kind used with [F]T1 lines (in my case a MicroVAX with a DSV11 card running
4.3BSD-Quasijarus) to a Copper Mountain SDSL line. Apparently it was
manufactured and sold only very briefly because it is of no use to ordinary
sane people who just want to use their DSL lines like normal people do,
with an Ethernet interface. It is, however, useful to crazy people like
me who for non-objectively-justifiable emotional reasons refuse to use a
modern DSL router with an Ethernet interface and insist on using a Quasijarus
router instead, i.e., connecting the MicroVAX (via DSV11) to the SDSL line
*directly*, without an intervening Ethernet.

The CupreDSU is a V.35 DSU for the SDSL electrical signal and does for SDSL
what typical CSUs/DSUs do for T1 and DDS lines.

Copper Mountain has a page on their website listing all CPE compatible with
their DSLAMs, and according to that page Larscom is the only manufacturer
that ever made a simple DSU, which they called CupreDSU. All other CPE
listed there are Ethernet routers or bridges. The only other unit that
comes even close is the ADC Kentrox CopperSMART, which appears to be a
plain DSU at first glance, but it is also too smart for me. It knows about
Frame Relay frame format and has functions for tampering with the data
passing through it, while I want a raw DSU that passes bits through without
interpreting them in any way.

So I'm running around with my tongue out looking for a Larscom CupreDSU,
which apparently due to being totally useless to 99.9999% of DSL users
is absolute unobtainium. So if anyone here has one they can part with,
I offer $$$.

If I cannot find one, the only other alternative would be to build such a
DSU myself. Does anyone know anything about Copper Mountain SDSL Layer 1
electrical signal format? Has anyone ever tried to reverse-engineer a
CopperEdge DSLAM or one of the routers or bridges compatible with it?

Reading the manuals for various products (bridges, routers and the Larscom
unit in question) I see consistent references to something called SDSL
firmware, separate from the main unit firmware, which is often upgradeable.
This makes me strongly suspect that all those products incorporate an SDSL
Layer 1 circuit licensed from Copper Mountain, and that the SDSL firmware
they are talking about is probably for a DSP used in it. The question is,
how is this circuit interfaced to the rest of an a typical router/bridge
product? Is this circuit implemented in separate chips and there is a
TTL/CMOS-level bit-serial interface lurking in between this circuit and
the rest of the router/bridge, or did they cram the entire SDSL circuit,
including the DSP and flash firmware, into an ASIC together with other
unrelated things? Has anyone poked inside one of those routers/bridges?

TIA for any help,

MS
Received on Sun Jan 02 2005 - 14:45:52 GMT