Comtrol is well-known for its multiport serial systems, and several years ago we reviewed its excellent RocketModem and RocketPort systems for UNIX. Porting these boards to Linux is a natural step. The RocketPort Plus lineup has several configurations, including a two-port model that we tested. The RocketPort Plus is designed to offer multiple high-speed RS232 ports that can be configured as any COM device.

The RocketPort Plus package we received included the board, a CD-ROM with software and documentation (the software is for several operating systems), an updated Linux driver on diskette, and a three-page installation and configuration procedure. More complete documentation must be accessed off the CD-ROM, but most administrators and users will be able to install the RocketPort Plus with the simple instructions provided on the printed sheets. A neat feature of the Comtrol boards are that they are surge and static protected at the port interface, protecting the system they are installed in.

Physically, the RocketPort Plus is a normal-sized PCI card with two male DB9 RS232 ports on the back plane. The board chip density is low, using two ASICs (using 44MHz processors) for the port control. The package also includes a loopback connector to allow testing of the ports. Installation of the RocketPort Plus is simple: install the hardware in any available PCI slot, then load the driver from either the supplied floppy or from an update on the Comtrol Web site, and run an install make script. In some cases you may have to recompile the Comtrol RocketPort Plus drivers, but we didn’t have to on our test systems.

You next need to tell Linux to load the drivers for the RocketPort Plus when booting. This will not be necessary for all versions of Linux: both RedHat and Debian Linux (in fact any system using the System V init file setup) can handle the configuration automatically. For non-System V systems, a simple edit of the /etc/rc.d/rc.S file takes care of the process. The PCI board installation requires a manual edit of a RocketPort Plus configuration script to remove ISA/EISA board configuration information. The gettys for the ports can be set automatically or manually by using inittab. The entire installation and configuration option took us an average of ten minutes.

To achieve baud rates higher than 38,400 the ports have to be remapped. A utility supplied with the RocketPort Plus allows port speeds of 57,600 (ideal for external V.90 modems), 115,200 (good for ISDN modems), and a maximum speed of 921kbps. The complexity of remapping the baud rates depends on the currency of your Linux system. If it has the most recent version of libc, remapping the ports doesn’t require the RocketPort Plus utility at all. Older Linux libc versions require a little more effort, but the end result is the same.

We tested the RocketPort Plus in three different systems: RedHat 6.2, SuSe 7.1, and Caldera OpenLinux 2.4 (an older release used as one of our application servers). In all three cases the RocketPort Plus installed and configured easily, and worked flawlessly. We tried several external devices connected to the two ports, ranging from modems (both V.90 and ISDN) through to high-speed serial color laser printers and a POS (point-of-sale) terminal. Configuring the different speeds using inittab is simple, or you can simply edit the getty files yourself. We tested both ports set to the speed of 230,400 baud, leading to two test PCs configured as X terminals. With both ports driven using animation scripts, the RocketPort Plus handled the traffic with aplomb, giving an average sustained throughput just below 200,000 baud. We didn’t benchmark the board to the claimed maximum speed of 921kbps because we couldn’t generate a reliable measurement at these speeds.

As with most multiport serial devices, there’s little glamour in these devices. They just work, fast, and easily. As with every other Comtrol device we’ve tested, the RocketPort Plus performs as expected. If you need two (or more) configurable fast serial ports, this is an excellent device.

RocketPort Plus 2-port PCI
6655 Wedgwood Road
Suite 120
MN 55311-3646
(800) 926-6876

Summary: If 921kbps isn’t fast enough for your serial ports, we don’t know where you should turn. Superfast, surge-protected serial ports for your Linux system make this board a winner.