Converting 2400 Baud Modems to 9600's

Oct 25 18:17 UTC 1991

*************************************************************************
How to upgrade your 24oo modem into a 96oo baud.  (US Robotics compatible
of course)
                                Written By
                   Death Bringer (CPT/Info-Net/IRA)

                                06/7/91


Be sure to turn off your modem before you begin.

First of all, you need to go to your nearby electronics store, don't try
to go to Radio Shack, their parts have their own model numbers and you'll
have a hell of a time getting the parts you need.  This upgrading of your
modem will not work on old hayes modems, but they will work on any clone
maker of modems (everex, practical peripherals, anchor, ati, intel, etc.)
It will only work with modems with the Intel Chipset.

This technique widens the band width by using a different chip that is
similiar to the chip already in your modem.

Parts Needed:
16550 UART
L4313545  IC
SC11020CN IC
L8730183  IC

First of all, check to see if your biggest chips are soldered or socketed.
if they are soldered, you'll have to de-solder the chips before you begin.
After you get that done, replace the 8250 UART with the 16550 UART. (16550
UARTs are required for 9600+ speeds).  The other 1 or 2 chip(s) need(s)
to replaced with INTEL L4313545 instead of the chip that is already there.
If your modem has another socket or more, than you are in luck, you can
purchase a chip from US Robotics, and make your modem faster than 9600.
If you don't have the socket, than you can only go 9600.  I'll get the
chip number to you in the next edition and explain how and where to
install it.  I am working on a way for the people (like me) that do not have
the extra socket in their modem to speed up the rates.  I am working on a way
to piggy back the chip.  I'll get back to you.  There should be a 22 pin
chip on your modem also with a model number of SC11005CN or some where close
to it.  Replace it with the SC11020CN.  Also, replace the L8630173 with the
L8730183 chip.  If you have any suggestions or questions, you can locate me 
through Compuserve USER ID 74702,97524

*****OPTIONAL, LAP-M Error correction*****

Adding error correction is rather simple.  For this these parts are
necessary:

Potentiometer. This is a 5k audio taper variable resistor.

Capacitor. Any non-polarized 1.0 to 1.5 uf cap should do.

100 ohm resistor - quarter or half watt.

Wire

Solder, soldering iron, etc.

Solder one end of the capacitor to PIN 1 of the phone line input jack
|-------------------|
|                   \ line in         ::
|                   \ phone in        ::
|-----------|||||||||            pin 1^



If your modem is external, the diagram looks like this.
 

|------------------|
|                 /|
|                 ||RS-232 port
|                 \|                  ::
|                |-|line in           ::
|                |-|             pin 1^
|                |-|phone in
|                |-|
|------------------|
This should be on the back of the modem.
Pin one should the farthest on the bottom left.

Solder the other end of the capacitor to the center lug of the potentiometer
(there are three lugs on this critter). Solder one end of the resistor to the
PIN 4 of the line input jack. Solder the other end of the resistor
to either one of the remaining outside lugs of the potentiometer. Doesn't
matter which one.

-------------------------------------------------------------------------

ADDITION TO ORIGNAL FILE - 6/15/91 
Bill McCauley & Dark Spyre/Dr. Brains/Ryan Schwartz/Lamer/Loser

First, a personal recomendation. _THIS WORKS!!!_  I have been plagued with
2400 baud for some time. I hate waiting for the transfer to finish so that
i can use the phone.  Threw the gismo together in about 10 or 15 minutes,
took another five to adjust the pot for best results on my worst
conection, and guess what? No more slow connections!

-------------------------------------------------------------------------

Have Fun!

I am working on cheap ways to install V.32/V.42bis on your modified modem


*************************Updated, 6/16/91********************************

Installing V.42bis:

1) You will need to purchase a 27C512 ROM chip.
2) You will need to purchase a Sony CXK58257P-12L (or equivalent) Ram chip.
3) Install the Rom in the Supervisor (SUP) socket.
4) Install the Ram in the Ram socket.
5) Make up two 3 pin jumpers for P9 and P10 with pins 1 and 2 jumpered
on one and pins 2 and 3 jumpered on the other.  Connect the vacant pin 1
on the one to the vacant pin 3 on the other with a jumper wire.
6) Remove the jumpers on P9 and P10.
7) Install the jumper with pins 1 and 2 connected together on P9.
8) Connect the jumper with pins 2 and 3 connected together on P10.


DeathBringer '91

response 2 of 40:

Oct 25 22:51 UTC 1991

   It sounds perfectly bizarre, to me.  Using *which* Intel chip set?
Using *which* revision of that chip?
 
   The most absurd thing in the above item is the implicit assumption
that any modem using the Intel chips will have its PC board identical
to this!

   Now, I have no doubt this works on a specific modem with a specific
rev of the modem chip, but to generalize like this is either stupid,
or perhaps malicious?

response 4 of 40:

Oct 26 01:34 UTC 1991

Let's have a show of hands.  How many of you would trust their
2400-baud modems to a guy with a pseudo like Death Bringer?

response 6 of 40:

Oct 26 10:24 UTC 1991

Let's see here... I got 1,2,3   2400 baud modems.  Humm.  One of em's
got to hahe the right Intel chippies in it...

response 8 of 40:

Oct 26 21:11 UTC 1991

If the CIS address is bogus, that's a pointer. I passed this info to one
of the internet lists I am on, and was very embarresed when I saw the
responses here, of course I sent immediately another mail saying don't do it.

If intel has a modem chipset as described, it is possible that you can
buy a different ROM from intel to implement different compression algorithms.
The person may not know the electronic terminology well enough to distinguish
EEPROM and ROM. Who knows? Alltogether it looks pretty unreliable.
I am realy embarressed for being that stupid.

response 10 of 40:

Oct 27 01:16 UTC 1991

I like the 27C512 part.  "See how well it runs with all 1's."

response 12 of 40:

Oct 28 03:22 UTC 1991

Gee, let me dig up my instructions for the 33MHz Vic-20...

response 14 of 40:

Jan 20 05:11 UTC 1992

You might be interested to know that the supposed "this works" response in
that file was pulled from a file for a line noise filter and modified slightly.

response 16 of 40:

Apr 4 10:51 UTC 1996

Yeah, I made the little thing to supress line noise.  Helped a bunch at 2400
back home where we have lot's of wire in the house.  I think the Cap
compensates for inductive loading in the non-twisted pairs.  I find the little
box to be a *problem* beyond 2400 however.  It clamps the voltage swings too
much to talk fast.  But, a couple passive devices on the wire sure are not
going to send 10 or 11 bits in a trellis code for every 8 bits you want to
send.  :)

response 18 of 40:

Feb 19 12:58 UTC 2001

So, how much does DSL and Cable modem service cost these days?  Last I heard
just basic cable TV runs $360 a year.  How much more for cable mode?  How
about DSL?

response 20 of 40:

Feb 19 20:30 UTC 2001

Re #18: I've seen DSL advertised for around $50/month, lately.  Cable
modem service seems to run $10-$20 cheaper, but you have to buy cable on
top of that.

A lot no doubt depends on your local cable and telephone monopolies,
though.

response 22 of 40:

Feb 20 04:53 UTC 2001

I have a modem with a pop-out connector.  (A Megahertz XJACK
28.8...which I've upgraded to 33.6 with a firmware upgrade.)  It's great
for occasional use, which is what I wanted it for, because there's no
cable to lose.  I agree it'd be a bit flimsy if you were using it
constantly, every day, though -- it looks like tripping over the phone
cord and tugging it *just* right would snap the whole thing right off. 
The other potential problem is that, since the phone cord plugs in
vertically, and the plug end protrudes below the card, it interferes
with any other card that has a cable connection.  I can't easily have
both it and my ethernet card connected at the same time.  Again, for me
this isn't a problem, though.

Recently I've started seeing 10baseT ethernet cards with the same kind
of connector.  Given the stiffer and heavier nature of 10baseT cable,
this strikes me as a terrible idea.

response 24 of 40:

Feb 20 12:33 UTC 2001

Given that only two of the wires in the whole connector matter, and that you
know how to solder, I'd say that any cable which has the right connector ought
to be sufficient.