When I got the MultiTech USB modem, I was running Windows 95B (OSR 2.0) on all of my computers.
I quickly discovered that the USB extensions for Windows 95 (Win 95B upgraded with these extensions is known as OSR 2.1) do not have complete support for USB, and the MultiTech modem did not work with this version of Windows. According to their tech support personnel, the MultiTech modem only works with Windows 95C (also known as OSR 2.5) or Windows 98.
Windows 95C is pretty hard to acquire these days. When it was being shipped, it came only with new PC's, but most new PC's now have Windows 98. So, I gritted my teeth, reformatted my C partition and installed Windows 98. Fortunately I'd had the foresight to put GPL and all my other applications and data on a separate D partition, which remained intact.
With Windows 98 on board, the MultiTech modem installed itself just fine when I plugged it into the USB port.
With Windows 98 installed and talking to the MultiTech modem, I figured I was golden. However, apparently I received a modem with a rare defect, because the modem would not raise a dial tone. I could get it to work only by taking a phone on the same circuit off the hook before directing the modem to dial, and leaving the phone off hook all the time the modem was connected to my ISP.
A call to MultiTech revealed this was indeed a rare defect. No one I talked to there, incluing several tech support personnel and the modem's designer himself, had ever heard of this problem before.
They had a new modem at my door in a couple of days. This one works great!
The 3Com modem ships with a telephone cable, but no serial port cable and no USB cable. I had a serial port modem cable lying around (which I needed to install the firmware flash upgrade; see below) but I had to hunt down a USB cable. I found one at Wal-Mart, of all places.
This modem is advertised as supporting USB connection (as well as connection to a serial port) but as shipped, its drivers are not functional for USB and a firmware flash upgrade is necessary to make it function as a USB device. USB drivers and the firmware flash upgrade became available from the 3Com Web site shortly after I received the modem.
The flash upgrade required that I first install the modem as a serial port device (using the drivers that came with the modem) and then perform the flash upgrade using the file I downloaded from the Web site. Then I had to deinstall the modem, delete about a half dozen files by hand from my Windows, Windows\System, and Windows\Inf folders, and reinstall the modem as a USB device.
The documentation which came with the flash upgrade explained this clearly, but it did tell me to delete some files which turned out not to exist. I don't know about you, but deleting files from my Windows and Windows\System folders makes me nervous!
I found the installation of the original drivers to be confusing, because the documentation said to load drivers from the CD-ROM that came with the modem, but that contained a plethora of drivers for many modems, and it was not clear to me which one was correct for this modem. A floppy containing drivers for that modem also came with it, and that had only two drivers. It was still not clear which was correct, but I made a guess, and it worked.
The 3Com documentation did not mention USB or Windows 98 in any way, except for a small one page leaflet which told me to go to the Web site to download the USB drivers.
Once the flash upgrade was performed and the USB drivers were installed, the 3Com modem connected to my ISP on the first attempt.
3Com assures me that this modem is now being shipped with USB drivers in the package. Presumably the proper firmware is also on board.
In preliminary testing on VROC, I was unable to sustain a connection in GPL with the 3Com USB modem, either as a host or as a client. Disconnects occurred within less than a minute after connecting. I made many attempts to several hosts, and a number of clients attempted to connect to me when I hosted. None of the connections was sustained long enough to run a lap.
After I deleted the MultiTech USB modem driver from Control Panel/Modems, and rebooted, this problem appeared to go away. Apparently the drivers for the two modems were conflicting. I do know that when I had both modems attached to the computer, when I tried to dial through the MultiTech, the 3Com dialed instead.
I also changed the 3Com's connect speed in DUN from the default of 115200 to 230400, the maximum it would allow. I don't know if this made any difference, but it seemed like a good idea, since it affects the speed at which the modem communicates with the USB controller in the computer and therefore presumably the USB packet size.
When running GPL on a Voodoo or Voodoo 2 card, there is a reduction in frame rate when a USB modem is active in the background whether or not GPL is actually using the USB modem. Here are some tests I did:
I set graphics options to get 36 fps when running on the Voodoo card (see below).
When the modem was not active, the choice of joystick driver seemed to make no difference.
Frame rate was significantly degraded when the USB modem was connected to an ISP. It was worse when using the Generic controller driver, which placed my digital game controller in legacy (non-digital) mode (see below).
*except low 30's approaching pits (test was at Zandvoort)
With the 3Com USB modem active, frame rate was degraded but not as much as with the MultiTech, particularly when using the Generic driver:
The frame rate seemed to be very sensitive to the number of objects in the forward view (even when those objects were hidden behind other objects. It also degraded dramatically when I generated tire smoke.
Another strange thing happened with the 3Com modem active: the buttons on the bottom corners of GPL's menus flashed in a random pattern (almost like dying neon signs). This is not like the flickering I've seen before when running on a Rendition card, which is more rapid and regular and happens on more parts of the screen (although this did happen as well, after I switched from the Generic driver back to the DirectInput driver). I've never seen the neon-flickering buttons before.
All tests were with a Voodoo 1 card on an ASUS P2B/P2-350 with Win98.
I am using a PDPI L4 digital game controller, which operates in legacy mode (ie non-digital) when using the Generic driver.
GPL was run in Training mode at Zandvoort.
When a USB modem was active, it was connected to an ISP, and a program called Stay Connected! was used to keep it connected to the ISP. This transmits a few bytes every minute or so to somewhere on the Internet to kep the ISP from disconnecting due to lack of activity.