Timothy
Parker Consulting Incorporated
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RocketModem: A clever alternative for modems Stacks of modems and a nest of both serial and telephone cables behind them are a common sight for many UNIX servers. Most systems still support modems through multiport serial cards, sharing modems and terminals on a breakout box. A clever alternative to this approach, and one which cleans up the external cable and modem stack mess, is Comtrol’s RocketModem. RocketModem is an ISA board with four or eight fax modems built in, so all you need do is plug telephone cables into the back of your server. The RocketModem modem is long and many newer PCI-based motherboards may have difficulty accepting this card. We had to shuffle an existing long card out of our packed server, a dual-Pentium ALR Revolution 2XL, for this review. Since the card we removed was a multiport serial card used to support mostly modems, this was no great loss. However, prospective buyers would be wise to make sure that a 13.5-inch long board will fit in their ISA-slots. CPUs, cache, and other paraphernalia tend to block the ISA slots on many motherboards. The documentation included with the board refers to a PCI version of the RocketModem, but we couldn’t confirm its existence. We tested the eight-port RocketModem board. It is heavily populated with daughterboards providing the modem functionality. The backplane has eight standard telephone slots arranged one on top of the other. Installing the card was simple enough, although plugging in eight telephone cables was a wee bit finicky with other projections from our server’s backplane. Luckily, this operation will likely be done only once in most systems, and the ability to neatly tie and route all eight telephone cords into a single larger cable run makes the back of the server dramatically neater. We were provided with beta copies of the latest SCO OpenServer drivers for RocketModem, which installed easily enough using scoadmin. Valid I/O ranges for the card must be chosen, but the defaults will be fine for most systems unless you have a number of multiport cards already installed. After a kernel rebuild and reboot, the RocketModem ports are active. The RocketModem board employs a dedicated 36MHz processor to help off-load the host CPU but seems to lack any cache. A maximum of four RocketModem boards can be installed in a computer, but we suspect there are few systems that need that many (or have the slots for them). Each port on the RocketModem is capable of handling all of today’s standard asynchronous speeds for both data and fax. (The newer 56kbps one-way modem system is not supported, but that’s not an issue for most SCO systems as an expensive server-end modem is required to allow users to dial in at 56kbps.) We tested the RocketModem modem by setting two ports up as fax ports, employing Faximum Software’s (Vancouver, BC) excellent Faximum package. We had these two ports send faxes to each other in a continual loop for load testing, while the other six ports were divided into three banks. Two ports called another two ports and used Perl scripts to sent large files back and forth, while the last two ports connected to an ISP and ran a pre-scripted set of Web page loads. We kept the ALR server with the RocketModem card under this load for one hour and monitored performance. The RocketModem’s impact on the system was small, even with all eight ports blazing along, and so should cause no performance concern for system administrators. Under normal dial-in loads, we suspect the RocketModem impact on the host CPU will be barely noticeable. The limiting factor in our tests was disk access, as every connection tried to read and write to our SCSI drive subsystem. Windows NT drivers are included with the system, too, so we moved the RocketModem to our Windows NT server (also an ALR Revolution 2XL). Windows network drivers must be installed for the RocketModem to work (they need the loopback driver). Installation is simple using the Add Adapter network window. The modems are configured through the Modem applet, which detects the RocketModem card and the proper number of modem ports immediately. Some conflicts may occur with IRQs, but these can be manually set through a Setup program. Using Delrina (San Jose, CA) WinFax and WinComm we repeated the load testing and found much the same result: minimal impact on the host operating system. The Windows NT system did seem a little more affected than SCO OpenServer, but that’s probably due to operating system design. The Comtrol RocketModem is not an inexpensive board. However, to put the cost in perspective you have to calculate the cost of four or eight external V.34 modems, a multi-port card to drive them all, and cables. When viewed in this light, the RocketModem is not excessively priced. True, external modem prices have dropped dramatically lately, but the convenience of a plug-in dedicated modem controller is worth something extra to most system administrators. Throughout our testing period the RocketModem performed perfectly. It handles data and fax with equal aplomb. If you don’t have a stack of modems you want to use on a multiport serial card, the RocketModem is a perfect way to get modem functionality and a neater server in one. As a plug-in remote access server card, the RocketModem presents an attractive option to more expensive and complex network devices, too. |
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