KVM Switches Roundup

A review of six KVM switches with a variety of features.

Joel Sloss

July 1, 1997

18 Min Read
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Eliminating Computer Room Clutter

How many monitors, keyboards, andmouse devices do you have spread around your computer rooms? Probably one setfor each server, right? This configuration not only results in a lot of clutterthat makes working around your machines difficult, but monitors require hugeamounts of electricity and generate a lot of heat.

Keyboard/video/mouse (KVM) switches have been around for a long time, butnot for Windows NT. The problem plaguing NT and preventing the use of older KVMswitches is that if you take away the mouse in NT (particularly a PS/2-stylemouse) for even a moment, you lose cursor control. You either have to reboot thesystem to regain cursor control or learn how to navigate using the keyboard. IfNT doesn't see the mouse or the keyboard when it boots, it won't load thedrivers and you won't be able to use either device. Therefore, many older KVMswitches won't work with NT because hitting the button on the switch is the sameas disconnecting the device.

Newer switches address this problem by providing a keep-alive signal to thecomputer's peripheral bus. As far as NT is concerned, regardless of what systemyou switch to, the peripherals are available.

The Windows NT Magazine Lab reviewed six KVM switches with featuresranging from keyboard and software controls to hard switches. Different modelsoffer varying levels of functionality (and several vendors offer multipleversions, depending on what you want), number and types of ports and systemssupported, extensibility, and price.

Our tests included five 8-port switches and one 4-port switch, with a mixof AT-style, serial, and PS/2 connectors, and DB15 video ports (although severalswitches used proprietary connectors and cables). Most of the units we testedhad 12-foot cable sets (we didn't include these in the prices we list herebecause some switches used longer cables and some used shorter cables).

How We Tested
We didn't run the KVM switches through every possible configuration withevery kind of peripheral and system. Instead, we tested the switches for basicfunctionality with various configurations. We attached switches that supportedvarious connections (e.g., PS/2 DIN8 and AT-style DIN5 connectors) to allavailable device types at the same time. For switches that didn't supportvarious connections, we simply attached those device types that the switchessupported.

We tested the KVM switches using primarily Intel-based workstations,although several of the RISC machines in our lab, such as Alphas with PS/2connectors, had no difficulty with the tests. We did not test the switches onSun Microsystems or Macintosh systems, but the trouble-free operations weexperienced with the Intel systems indicated that the switches should work withthese other systems, provided you use the proper cables.

The Big Picture
The Lab's overall experience testing these switches was positive, so much sothat we would like to keep them all--each product made our lives easy. We wereable to use these switches to keep more than 35 workstations up and running atthe same time. Before we started using the switches, we had to spread out allthese systems across the lab, each with its own monitor, keyboard, and mouse.Once we installed the switches, we were able to condense the systems onto just afew racks (no more running around the room to work on each system), eliminate alot of excess heat from the room, and cut our electric bills.

When deciding which switch to buy, you need to consider what kind ofsystems you have, the types of systems you have, how far apart they are, andwhether you need to control several computer rooms from one location. You alsoneed to consider how you are configured and whether you have racks that needhot-key control.

Most of the switches we tested are extensible--you can connect several tocontrol many more systems at once--and offer reliable operation. Which switchyou select depends on your needs, but any one of them is well worth theinvestment.

8-Port PS/2 Server Switch
Network Technologies, Inc.'s (NTI) 8-Port PS/2 Server Switch offersstraightforward functionality for system switching. NTI offers switches withboth front-panel buttons and hot keys for selecting attached computers(PS/2-style or others using adapter cables), models that support up to 48systems, and cable lengths of up to 500 feet.

We reviewed the 8-port model, and it worked without a flaw throughout ourtests. The switch offers standard PS/2 and DB15 video connectors, so setting upthe cabling was easy. The switch passed through the video signal withoutdistortion, and we encountered only a few times when the mouse controlling theattached systems did not work properly during the boot cycle, because of eithera driver failure or a bad connection.

The front-panel buttons on the 8-port switch serve several purposes. If youpress one of these buttons quickly, you select that individual channel, and it'sLED. If you press one of these buttons and hold it in for more than half asecond, the switch enters one of three special operation modes (you need topress and hold the button several times to cycle through all three modes).

In the first mode (scan), the switch cycles through all channels at apredetermined interval that you set. In the second mode (one-to-many broadcast),you can send keyboard signals to all attached systems simultaneously. This modeis useful for rebooting and executing the same program on all computers. The NTI8-Port PS/2 Server Switch is the only switch we reviewed that offered thisfunctionality. In the last mode (command), you can enable keyboard control (hotkeys) for the switch--you can also engage command mode by pressing Ctrl-Shift-8or * on the number pad. In this mode, the i and d keys incrementand decrement the channel number, the s key turns scanning on and off,the t key followed by a number sets the scan interval, the p keyand a number select a specific port, and the b key enables broadcasting.(NTI warns against using broadcasting while a system is rebooting.)

NTI doesn't support cascading multiple switches, but if you buy the 48-portversion, you can attach almost the same number of computers as if you were usingseveral of the competing models. The only drawback to using the 8-Port PS/2Server Switch is that it doesn't provide an onscreen display of the currentchannel selection. It does offer a remote-operation capability through a specialport (with an optional remote selector), but even the remote selector doesn'toffer an onscreen display to show you which system you are using. The 8-PortPS/2 Server Switch worked well for us, and it can serve as a basic, no-frillsswitch for eliminating clutter in any MIS department.

AutoView Commander
Whether you're searching for a reliable, basic KVM switch or one withadvanced functions, such as extensibility and programmability, you'll want totake a look at Cybex Computer Products' AutoView Commander. We tested a small,rack-mountable AutoView Commander 8-port switch (a 4-port version is available)that supports various device types (PS/2-style keyboard and mouse, AT-stylekeyboard, and serial mouse). The switch we reviewed required proprietary cablesbetween the switch and the attached systems (although Cybex offers anotherAutoView switch that uses standard PS/2 cables). The proprietary nature of theswitch means that Cybex can use the same connector for all ports on the box,which makes the switch smaller and lets you mix and match the devices attached(i.e., some can be AT-style and some can be PS/2). However, this approach alsomeans you must buy your cables from Cybex, which offers cable lengths of 6 feet,8 feet, 15 feet, and 30 feet.

The AutoView Commander has programmable functions, such as autoscanning(automatically cycling through the attached systems at a time interval you set)and channel naming (up to 14 characters so that you don't have to remember whichletter goes to which computer). For extensibility, you can cascade 8 additionalAutoView Commanders in a star configuration, for a total of 64 switchableports--enough to handle a pretty good sized data center.

One handy feature of the AutoView Commander is that it can stay functionalafter a power failure. It can draw power directly from the systems attachedthrough the keyboard or mouse ports so that if the switch loses power, it cankeep running and maintain signal integrity. During the power failure, you can'tswitch the AutoView Commander and it won't display anything, but it leaves thekeep-alive signal going so that the systems don't think they've lost touch withtheir peripherals (you'll notice that the power status lights also remain lit).

AutoView Commander's best feature is that it lets you switch between theattached systems either by pushing the front-panel buttons or by using hot keys.Using the buttons can be cumbersome because you don't have a lot of room on theswitch to add labels over the buttons to tell you which systems they go to--youhave only a letter identifying the channel. To use the buttons, you either haveto place the unit on your workstation table or get the RSP Commander (a remoteswitching module) to operate the switch from a distance.

A better option for controlling the switch is keyboard-only control(hands-free operation). Simply hit the Ctrl key twice within a second, and anonscreen menu pops up that lets you select a system from a list of channelletters using the arrow and Enter keys. Whether you use the front-panel buttonsor the hot keys on the keyboard, an onscreen identifier that shows for aboutfive seconds lets you know what system you are operating. An LED over thechannel button also lights up when you select that channel.

The only problem the Lab experienced with the AutoView Commander was thatone of its video ports slightly warped and skewed the image about an inch to theleft on the monitor. Other than that one port, the video pass-through qualitywas fine, even at high resolutions. The switch worked flawlessly and neverdropped a mouse connection. Switch time either using a button or the keyboard isa little slow (you notice a pause as the switch engages the next circuit), butthis interruption is annoying only when you need to scan rapidly through manysystems to monitor tasks. For the price, you get a lot of functionality, cleanNT operation, and a reliable unit with the AutoView Commander.

MasterConsole MCP8
Raritan Computer's MasterConsole MCP8 is one of the more versatile units wereviewed. We tested the 8-port version of the switch (2-port, 4-port, and16-port units are also available). You can connect up to 64 computers, such asPCs, Macs, and Sun Microsystems' systems that use PS/2-style, AT-style, andserial devices (or Apple Data Bus--ADB), in any mix by cascading switches. Youcan locate computers up to 60 feet from the switch and add a second keyboard,monitor, and mouse 150 feet from the switch.

You can use MasterConsole's main up and down buttons or hot keys to selectchannels and perform other functions such as autoscan. The MasterConsole unitthe Lab reviewed is not programmable like the Cybex and Apex units. For thisfunctionality, you need to purchase the MasterView option ($150 when purchasedwith the MasterConsole switch or $345 when purchased separately), which providesfeatures such as channel naming and onscreen control from pop-up menus.

To enable the hot keys, press the Scroll Lock key twice within a half asecond. After you enter this mode, you can use the arrow keys to navigatebetween channels and banks (for controlling more than one MasterConsole) orenter a number and hit the Enter key to select a specific channel. The drawbackto both approaches is that you don't know which system you are looking at unlessyou know the numbers (or bank letters) that refer to those systems. Again, youneed the MasterView option to see an onscreen display and define channel names(this limitation is a tad bothersome in such a high-end unit).

MasterConsole lets you create a 64-system control center by daisy-chainingfour 16-port units. With proprietary cabling (heavy-duty and double-shielded)that can reach 60 feet, other switching modules, and optional repeaters that canboost the signal, you can piece together a system that will control 1024computers, 300 feet away.

Even so, we found the cabling somewhat difficult to deal with. Because theproprietary cables are so well shielded, they are bulky and stiff, which makesbundling the cabling to get it out of the way difficult. The cabling arrangementwe received (we asked for the ability to have various connections) left us witha jumble of cables: The main cables that come from the switch are paired suchthat each cable connects two computers to the switch. One of the main cablespairs two PS/2 mouse connectors, each serving two computers, and another maincable pairs two video connectors and two PS/2 keyboard connectors to serve twocomputers. You can attach converters to connect AT-style keyboard, serial mouse,or ADB, depending on what you need.

We were surprised that the switch connectors and cables were split intopairs--four PS/2 mouse connectors, each serving two computers, and four videoand PS/2 keyboard connectors, each serving two computers. Ultimately, thisapproach makes sense, because it lets Raritan make heavily shielded cabling toreach the great distances (60 feet) without repeaters. However, the connectorsand cables were confusing to set up and made quite a mess behind the rack.

MasterConsole is available in either a 19" or 24" rack-mountablechassis, and you can get remote control units to extend your reach. With theappropriate options, you can have dual-access (to set up another controlcenter), multiple monitors (a video splitter), and many-to-one sharing (up tofour KVM stations can control one PC).

Operationally, we had no complaints with the MasterConsole. It worked withall the systems we tested and the video was clear, even at high resolutions. Theswitch never failed on boot-up or lost connections. With the autoscan andautoskip (skipping inactive channels during manual switching or autoscan)features, we believe that the MasterConsole would work great in any data centerenvironment, although you should consider getting the MasterView unit for addedease-of-use.

Outlook 8-Port Concentrator EL-80DT
Of the switches the Lab tested, Apex PC Solutions' Outlook 8-PortConcentrator EL-80DT was the cleanest and easiest unit to use. We just pluggedit in and it worked--no fuss or confusion with the cables.

The Outlook is a single rack-space unit, so it fits nicely into a rack ofnetwork hardware without taking up too much room (several server manufacturersequip their rack configurations with the Outlook). The switch operatescompletely hands free (no buttons). As a result, you don't need to place thisunit within reach on your desk or computer table. In fact, you're limited onlyby the maximum KVM cable length (up to 50 feet between the switch and thecomputer, depending on which type you have) for where you can put it.

Outlook's hands-free design means you control the switch from the attachedkeyboard and mouse. Pressing the Print Screen key brings up an onscreen menu ofoptions (overlayed on the computer's display) for selecting a system andprogramming the switch. Through a series of commands (which you select with thearrow and Enter keys), you set the system names that appear on screen to matchthe names of your servers and workstations. This way, you don't need to rememberwhich number on the switch goes to which computer. You can also perform otheradministrative functions, such as scanning through the ports on a set frequencyand displaying device settings. Pressing the Esc key backs you out of the menusand exits you from the firmware utility, returning control over the attachedsystems.

You can control up to 64 systems by using nine Outlook switches--onemaster, with each of the other eight plugged into its ports (each switch can be50 feet away from the master, and the attached computers can be 50 feet awayfrom the switch, for a total of 100 feet). You can switch between modules viathe firmware commands. The Outlook is PS/2 based only--no AT-style or serialconnectors--and has nine sets of ports: one concentrator for the KVM and eightsets for the actual systems. It supports RS/6000, Mac, serial mouse devices, andHP-9000 and Sun systems with inline adapters for computer rooms with more thanPCs or PC servers.

We never once lost a connection to a keyboard or mouse when running our NTtest systems from the Outlook. It switches quickly when you select anothersystem to view, and it maintains video signal integrity without blurring orshifting the image on the display. PS/2-based Alpha and PowerPC systems won'thave any trouble working with this switch. The best feature about the Outlook isthat it uses standard cable types instead of a proprietary connector or cable onthe switch that converts to the standard connectors on the systems.

One feature you won't find on the Outlook is one-to-many activityreplication so that you can repeat one action to all attached systems (Apex willhave announced plans to provide this functionality by publication time). Inaddition, one Outlook switch can't support more than eight systems withoutdaisy-chaining units (no 16-port or 32-port versions).

Overall, we found the Outlook to be very worthwhile and easy to use. Thecost for the unit (without the bundle of cables--although it does come with onekeyboard, one mouse, and one video cable) may seem high, but what you save inhassle, clutter, heat, and electricity more than makes up for it.

ServeView SVE-8U
Rose Electronics' ServeView SVE-8U switch had the most buttons and lights ofall the switches in our test group. Rather than providing an onscreen display,the ServeView provides a 2-character * 20-character fluorescent displayindicating status and mode (Rose Electronics offers other models that include anonscreen display instead of the built-in fluorescent display).

We tested an 8-port version of the ServeView, a versatile unit thatprovides support for PCs (PS/2 and AT-style), UNIX, Macintosh, and SunMicrosystems systems. You can daisy-chain switches to control up to 256 systems,but you have to use standard cable lengths of 5 feet, 10 feet, 20 feet, 35 feet,50 feet, 75 feet, and 100 feet. (Rose uses a proprietary connector and wiringscheme, so you must use its cables--however, Rose will custom build longercables on request--up to 200 feet.).

One feature that stands out on this switch over the other switches wetested is that you can upgrade the ServeView. A switch can start with 4 ports,and you can add 12 more ports in 4-port card increments.

You can manually control the ServeView using the buttons on the front panelor use hot keys to select systems (and even an RS232 port). We found the panelbuttons on the ServeView cumbersome. You have to press the membrane switchesfairly hard to engage them, and the buttons obviously require proximity to theswitch.

A better option is to use the hot keys. Pressing the left Ctrl key puts theswitch into command mode, so that you can select a specific channel (enter thenumber), turn to the next channel, begin autoscan (at programmable intervals),or reset the keyboard or mouse. The ServeView's built-in display tells youeverything it's doing. The ServeView also has other nice features to helpconserve and manage resources in your data center, such as flash ROM, automaticscreen-blanking (useful if your monitor doesn't have its own power management),and memory for keyboard states (such as Num Lock, Caps Lock, and Scroll Lock).

During our tests, we experienced a few functional difficulties. TheServeView didn't always switch reliably between attached systems--it wouldperiodically lose the mouse or not keep it present during system boot so thatthe driver didn't load. On the whole, however, the switch worked the way it wassupposed to in our NT enterprise testbed. The ServeView wasn't the cheapestswitch we reviewed, but features such as upgradeability should be fairly usefulto anyone with a growing data center.

StarView SV421
StarTech's StarView SV421 switch is a 4-port PC switch that offers severalfeatures and options worthy of consideration. First, it has ports for a PS/2keyboard and mouse, an AT-style keyboard and serial mouse, and standard DB15video. All these connections are standard, so you can use any kind of cables youwant. You can mix and match devices to fit your needs, with a standard cablelength of up to 30 feet, or 262 feet with extender options (powered repeaters).And with special brackets, you can install the StarView into a standard 19-inchrack.

You can cascade up to three levels of StarView SV421 switches, giving youcontrol over 64 separate computers (DIP switch settings tell the StarViews whichswitch is the master and which are the slaves). By pressing Ctrl-Alt-Shiftsimultaneously, entering the channel number you want, and then hitting the Enterkey, you can switch channels without taking your fingers off the keyboard.However, the method gets more complicated if you have multiple levels ofcascaded switches (you have to enter a series of numbers representing thedifferent units). Plus, you have no indication of which system you are actuallyaccessing, because the StarView doesn't provide an onscreen display--only anaudible beep lets you know that you've switched channels. You must be able tosee the LEDs on the front panel of the switch to see where you are pointed.

The StarView has one selection button on the front panel and one status LEDfor each channel. In a cascade environment, this button will cycle through onlythe systems attached. To select a specific channel, you must use the hot keys.

We encountered some initial minor operational difficulties with theStarView (it lost the PS/2 mouse connection to one of the workstations, andfixing the problem took several reboots and a certain amount of fiddling withthe cable). Since then, however, the switch has worked well. Video is clear atlow and high resolutions, the StarView switches reliably between channels, andthe standard cabling makes this switch easy to fit into a data center. StarViewalso offers an autoscan feature (you set the time interval with DIP switches)and channel stepping with the left and right Shift keys while you're in hot-keymode. The only major drawback we discovered was that the StarView switchprovides no indication--other than the LED--of which channel you are using.

For a basic and easy-to-use KVM switch that doesn't cost much and stillfunctions exactly the way it should in an NT environment, you can't go wrongwith any of the StarView switches (StarTech offers 2-port, 6-port, 8-port, and16-port versions, as well). In fact, the StarView 4-port switch costs the sameas switches we've purchased in the past that don't work well with NT and have nohot-key support.

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