Modems With Known Problems

Popular modem strings that we know work. You go to control panel then to the modem icon then to modem properties and look around for the "advanced" button which takes you to a window that has a box called "extra settings". This is where you enter the modem string. Usually it's a good idea to reboot after entering a string, just to be sure everything is starting from a known state.

here are the strings:

Rockwell HCF V.90 code is broken. Won't handshake until you set the client side to use kFlex only. This is only a workaround.needs latest Firmware to connect reliably. Get it at: WinModems

Try AT+MS=3DK56

Any kind of line noise and it handshakes forever with no connection established. Client side says computer not answering and client modem hangs up during handshake.

USR 56k Will not handshake properly, slow data xfer when it does connect. Use S32=34 to disable X2 S13=64 to disable fast retrains and download latest Firmware from:

AOpen 56k's (FM56-P) Only one version of firmware, doesn't appear to help at all. Modem doesn't connect, same phasing problem. Will not handshake, rapid disconnection's (within secs of establishing a connection) a lot of the time, the modem will just stop responding.

Cirrus Logic Handshake/phasing problem. Similar to the AOpens. Will not connect. (chipset CL-MD56xx typically) Needs latest firmware 6.04 or later. If worse comes to worse, I've been able to get the Cirrus Logics to connect with this init string: 

AT+MS=V34B,1,0,33600 or 

04 - DSP PATCH: 103.00

*NOTE* that the 4.08 is not the firmware number, although it looks like it. The 604 is actually the number you should look at--that's 6.04.

Compaq 56-df LT WinModem in disguise. Go to:

To get the latest SoftPaq from Compaq or update it to the latest LT WinModem drivers here

*NOTE* Installing the LT WinModem drivers will make the Voice functionality of the modem not work with the Compaq software on their computer.

Compaq/Rockwell Livingston's web site says something about put commas in and HCF modems force the modem to connect no faster than 41.333.

Acer Aspire I was able to get one to connect by adding 3 commas after the Rockwell HCF phone number, putting a 4th comma caused it to not connect at all. Update available from Acer ftp site:

The 00-INDEX.TXT file says it is, but the version information in the files is

LT WinModems (use +MS=V32 for 14400 connections which seems to work every time so far.) just long enough to download the new drivers from 

They need 5.49 or later. Kflex has been disabled in drivers v5.39+. to enable  K56flex instead of V.90, then you must use s38=1-v90=0

USR Sportster V.90 Speaking from past experience, I too was using a Sportster V.90
on a line incapable of supporting high V.90 connections. I would connect around 48K but would soon drop off after a minute or so. By experimenting, I found that I could keep the connection up
by setting a ceiling on the connect speed.


Which sets:
&M5 (Error Control only)
&N29 44,000 Ceiling
&U28 42666 Floor

Diamond Supra AT&F1E0W2+MS=56 Forces it to KFlex which, for some reason has a more reliable connection. Or is this doesn't work try AT&F1E0W2+ms=V34 for 33.6 speeds. Latest firmware is important.

SupraMax modems Disable V.90, or update drivers at:

Motorola SM56 Firmware website:

%B18 should limit the modem to 33.6 and allow it to connect

SoftK56 modem Firmware website:,000 WinModems

Look at the ATI responses for the individual modems and match it with modem in question.

PCtel modem Firmware website:,000 WinModems

Look at the ATI responses for the individual modems and match it with modem in question.

Telepath Modems Telepath Modems in Gateways are usually USR
sometimes Winmodems.

ESS Modem Well, I got so frustrated with this fine fine POS, I called the ESS Tech for some info on their chip set. There ONLY technician just told me to use the 56KES-X2 drivers off of and that the only manual reference I need for their chipset is the one 
for USR. Meaning it is a bastardized USR chipset.

Shark V.80 56k Most of them use Motorola chipset. Since most manufacturer uses the drivers straight from Motorola, here the Motorola URL for the modems and the drivers. Pay attention to the different kind of drivers with the identifier code.

Better Driver at v90mot67-2.exe

Acer modems We've found that some internal Acer modems of this vintage
(basically before Win95 shipped...) won't work reliably with a port speed of 115,200 - and the symptoms would often be strange (connect, drop, report no dialtone until a power cycle). When they didn't weird out they'd still disconnect frequently.

If the other end was an analog modem on a 57,600 serial port they'd work just fine, but calling anything capable of delivering traffic above that speed

Try setting the user's port speed to 57,600. It works for us

Xircom CreditCard Have him set S109=1, this will force K56Flex. Modem 56T If still no luck, set S38=0, this will force V.34

Emachines/Etowers Interestingly enough, in this Tech Support FAQ on their web site

they claim that "When the UART speed of 8250 is reported, this is erroneous." Aparently they use a virtual UART, so we now have a modem that not only farms off the processing of signals, it also doesn't even have a real 16550 UART.

AT&F&C1&D2&K3W1 or ATN0S37=14 for V.90
N0S37=13 for K56Flex or N0S37=12 for V.34

Global Village dropped the customer to 38400 port speed and set them to CTS-only for the flow control (recommended to me by Global Village)

Megahertz Cruise I have talked with Mac customers with Card (33.6) Powerbook 1400s. In one case, they had a Megahertz Cruise Card (33.6), but were unable to connect to the digital pool. Putting commas after the access number in the settings seems to work fine.

ATI0 = modem product code
"3 = modem firmware version
"6 = hardware info or link diagnostics
"7 = configuration screen (3Com/USR only)
"11 = specific information about modem operation

ATY11 = gives diagnostics for 3Com/USR modems., Inc. 
29 West Main Street, Martinsville, VA 24112
PO Box 1126, Martinsville, VA 24114
Tel: (276) 666-9533  or (800) 766-6861 or  Fax: (276) 666-9534