Project: Make a Netcomm RoadsterII USB Modem work in Windows 7 x64

Over the weekend, I had some hankering to get some voice-band dial-up modem action happening just for curiosity sake. I stumbled across my pair of old-reliable Netcomm Roadster II USB V.90 56k modems which seemed like good candidates for an easy set-up, not needing a power adapter and all.


The modems were model number AM5050 R3 and was made by Netcomm Australia, who have since changed to become Netcomm Wireless and no longer offer support for any of their older products. In fact, this product seemed to be a rush job in adapting their regular serial-based Roadster II that it retains the “Power Requirements: 7.5v DC 450mA” line which is not true for this model, and retains the case moulding cut-outs for DB9 serial (technically DE9) and 2.1mm DC barrel jack.


The modem itself dates back to about 1999, and was a full-speed USB device. the other modem of my pair had a case so damaged that I just operate it “bare PCB”, hence the dust accumulation, but at least you can see what it’s made of.


As we can see from the PCB, it is a Sirius product internally. Regardless, the last drivers available seem to be for Windows XP, and was archived by a member on Whirlpool. I had a copy of them myself. Knowing this modem is a USB-CDC device, I thought it would install just fine in Windows 7 x64 …

problem-driver… but alas, it wasn’t to be. Short searches online about this model didn’t give me hope, but I decided that it should work and there is no reason for it not to!

Getting Around It

Another device I know that is USB-CDC is the humble Arduino Leonardo. Looking at the .inf files gave me a clue – where it relies on usbser.sys, it is relying on Windows’ inbuilt USB-Serial CDC driver.

Another clue was this article by Portlandia Cloud Services which describes getting serial dial-up modems to work in Windows 7 – namely, .inf changes to allow for recognition as x64 capable drivers.

As a result, I set to work and made some changes to the inf – namely the highlighted lines were added (first one not entirely necessary):


As it turns out, that was all there was to it – just those lousy lines and bingo! After accepting a stern warning that the driver is not signed, it installed and its working!


This was mainly because the modem itself was USB-CDC compliant, meaning that the generic Windows-bundled x64 capable driver could be loaded in place to support the modem. The .inf changes were just to make Windows accept the configuration as compatible with x64.

It’s interesting to think that the vendor’s lack of support and updated drivers may have led to many perfectly good premium modems getting shelved because they couldn’t work with anything more modern than Windows XP.

Those who want to give it a shot can downloaded the modified .inf file as a .zip file.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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