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By default, Windows is limited to the default maximum speed of 115,200 bps for serial communications.
High speed UARTS modern modems can reach higher speeds support a lot more and may never reach full speed with the default settings. Also, compression can be enabled, sending even more data through the modem connection in less time.
The tweak presented here activates three options on the Modem applet in the Control Panel, that will allow you to set the modem to communicate with speeds of 230400, 460800 and 921600 bps.
Start the Registry editor by typing regedit.exe in a Run.. window, then go to the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Modem\0000
Note: If you have more than one modem, the last four characters of the string above will change to 0001,0002 and so on. Check under each sub-key until you find the modem you want to speed-up then continue with the step below.
Double-click on Properties (make a backup first) and you should notice that the 51st, 52nd, 53rd and 54th digits show "C2 01" or "84 03". Highlight these digits and then change them to "10 0e". Leave the rest of the digits unchanged.
After you close the Registry Editor, open the Modems panel (usually Control Panel:Modems:Your Modem:Properties:General or Control Panel:Phone and Modem Options). There should be three new maximum speed settings available: 230400, 460800 and 921600. Select the speed you wish to use and test with you modem to make sure it is compatible with the higher speed.
This tweak is listed in the network category. See all tweaks or click one of the latest tweaks listed below: