DUN and Serial Port Settings for GPL

Here's a synopsis of the DUN and serial port settings we have found to work most effectively for GPL so far. These help optimize the number of players that can join a game hosted over a serial port.

1. Install Win98 or DUN 1.2.

Randy feels DUN 1.2 isn't essential, and he hasn't installed it. However, Nate and I have observed markedly lower ping times with DUN 1.2, and it is also supposed to be more efficient in terms of CPU utilization. Our testing seems to support this.

You can get DUN 1.2 from Microsoft's download site; see here for more details. See How to Get Good Pings for an extensive discussion on installing DUN 1.2 and otherwise optimizing your DUN connection, although you should follow the instructions below if they conflict with what you read in "How to Get Good Pings". If you have Win98, you don't need to install DUN 1.2 because it comes with Win98.

Note: I don't have Win98 so Win98 users will have to infer from the following:

For Win95 + DUN 1.2:

2. Optimize your FIFO buffers.

Right click on your DUN connection and do the following:

• Properties
  • General tab
  • Configure button
    • Connection tab
    • Port Settings button
      • Use FIFO Buffers = checked
      • Transmit Buffer = one click from the left
      • Receive Buffer = one click from the left

Having small buffers means they get in a timely manner. This helps prevent lost packets on the receive side, and uses more of the available bandwidth on the send side.

3. Turn off error control and use Hardware flow control.

After setting the above, return to the Connection tab and turn off error control. Be sure to use Hardware flow control, not Software.

• Properties
  • General tab
  • Configure button
    • Connection tab
    • Advanced button
      • Use error control = UNchecked
      • Use flow control = checked
        • Hardware radio button is pressed

Error control apparently adds overhead that slows things down when sending lots of time-critical packets, so we eliminate it. It's more efficient to let the hardware do the flow control.

4. Turn off software compression.

Right click on your DUN connection and do the following:

• Properties
  • Server Types tab
  • Enable Software Compression = UNchecked

I believe it's an advantage to not attempt the compression of packets for games. For Web surfing and ownloading, compression makes sense, but since GPL's packets are already highly compressed, there's no point in having Windows try to compress them further. Turning this off can save some CPU cycles.

Differing requirements for Web surfing and gaming

Since using smaller buffers and eliminating compression and error control is not necessarily optimal for Web surfing and downloading, it might be handy to set up two DUN connections, one for racing and one for normal Web stuff.

However, note that the modem FIFO buffer settings apply to all modems and all DUN connections on your machine.