Mark Pickavance examines the many KVM options, as well as the alternatives and why some choices are better than others
Anyone who works with more than one computer rapidly runs into the problem of finding space for everything, thanks to the fact that PCs need a screen, a keyboard and mouse.
That can be super-annoying if you only have limited desk area and/or you need to access the second system only occasionally. You're cramped by equipment you only need to use maybe a couple of times a day, restricting the space you use all day. Surely there's a better way, right? Indeed, there is, and it's called a 'KVM'.
The Original KVM
The abbreviation KVM stands for 'keyboard video and mouse' and is used to describe a gadget that appeared when using PCs as servers first became popular. For many IT managers in this era, often the server hardware was wedged into a broom cupboard or similarly diminutive office space. In these locations, there often wasn't enough room to swing a cat, never mind provide multiple systems each with their own monitors and keyboards.
The first KVMs were frighteningly complicated, being a physical switch that allowed you to cable one monitor and keyboard to two or more computers, through horribly complicated wiring and switch mechanisms.
This was in the 1980s, prior the Windows era, so initially the mouse wasn't part of the problem, as there wasn't any practical use for it, since systems were running Novell Netware or DOS.
These devices weren't elegant, but they served their purpose - at least they would when they weren't going wrong or causing problems with the computers.
Having more machines necessitated increasingly intricate wiring and led to a greater likelihood that when you switched, for whatever reason, the target machine wouldn't respond to the newly connected keyboard.
Eventually hardware designs got better, changed from physical switches to electronic ones, and eventually they included PS/2 mouse ports.
Some were even independently powered, in an attempt to reduce predictable lock-ups. These can occur, because in a PC the keyboard has its own processor that it uses to poll the keys, and if the power is interrupted by the switching action, then the chip reinitialises and synchronisation with the PC can easily be lost.
They also had other restrictions on use, because the length of cable you could realistically extend VGA and a keyboard with wasn't massive, and longer wiring increases the possibility of inherent physical failure. New technologies like DVI, HDMI and USB also added to the number of wires, increasing the complexity and the likelihood of poor connections. So using a KVM could be both wonderful and annoying, depending on what sort of luck you normally experienced.
However, KVM makers did meet those challenges, and you can still buy a hardware KVM today that solves most of these problems.
The Modern KVM
Typically a modern hardware KVM will support USB mice and keyboards, in preference to PS/2, although some will offer a single port of that type for those that prefer to use it, like gamers.
Where they differ wildly is in respect of the video standards they include, with the cheapest offering to support only VGA displays. The problem with VGA is that it has timing issues with the highest resolutions, and this gets worse the length of the cable that connects the source(s) to the monitor increases. Some cheaper ones only support 1600 x 1200 resolutions, though the best offer 1080p or at least claim to.
More expensive designs support DVI, which is superior in numerous ways, and you can even get HDMI and DisplayPort KVMs if you wish. What isn't generally supported are multiple simultaneous display standards, for numerous reasons, including the hardware detection methods used by the PC.
Some KVMs, specifically targeting home users, support audio, but those aimed at the server environment tend to leave it out, if only to reduce the overall thickness of the cables.
That might seem a minor issue, but even with two computers there are plenty of cables, and when you get to four or more machines, it can rapidly descend into what seems like insulation-covered spaghetti.
The exact number of machines you can switch between using hardware is determined by the depth of your pockets, because above four things can get very pricey indeed. There are KVMs available that support 16, 32 and even 64 machines, but they often cost more than £1,000, due to the complexity of the wiring in them. Even good quality four-port designs using DVI can be more than £200, for those who want to control multiple systems easily.
These directly interfaced solutions aren't the only hardware option. Occasionally, the systems are geographically spread out, and for those you'll need an even more complicated and expensive device: the KVM switch.
KVM Switches
When I first came across these devices, it resulted in much head scratching about how they offer anything substantially different to cheaper KVM options. But now I understand their function, and it's mostly a range of capabilities that only system administrators would usually appreciate.
What a KVM network switch does is allow admins to access and control multiple machines using existing CAT5 cabling, sending mouse, keyboard, audio and video across the twisted pairs of a LAN cable. This allows for long ranges (50m), although the available video resolution is usually only a maximum of 1280 x 1024. And obviously the connection reduces the performance of that line if you're also using it for networking. To reduce this you can use dedicated CAT5 lines for KVM, although this doubles your network cabling requirement in a single stroke.
The solution to both the resolution and performance problems is to use fibre cabling, usually 10Gbe, allowing sufficient bandwidth for full control plus up to 4K resolution remote displays. The range on fibre is also much better, with 400m being the norm and single system linkage of 10km (yes, kilometres).
With those sorts of capabilities, these solutions are usually more than £2,000, and depending on how many computers you need to access, the combined cabling and switch costs can easily run into tens of thousands.
However, the ability to access one PC from another has been an inherent feature of Windows and also Linux for that matter, for some time. It requires no additional hardware, only software configuration, if you're prepared to accept some critical restrictions.
Remote Desktop (RDP)
First introduced with Windows XP, the Remote Desktop Protocol (RDP) is designed to allow one PC to take control of another for the purpose of using applications or remote administration.
The technology Microsoft employed was licensed from Citrix and its WinFrame software client. Citrix improved the underlying technology so RDP gained 24-bit colour support, sound and local resource mapping.
Under Windows 7 or 8.x it is a powerful tool that places access to the desktop of another distant PC in a windowed console and allows the user to do the majority of things that they could do locally.
However, there are limitations to what is basically a Windows call interception technology, mostly in respect of its inability to handle anything but 2D desktop graphics. It also can't smoothly stream video being played on a remote PC, because the system isn't designed to handle rapidly changing images.
Those points accepted, it has a number of very useful advantages over hardware KVMs, of whatever cost.
The obvious one is that distance isn't an issue, because with a VPN or port passing, you can access a PC on the other side of the world using RDP. That makes it popular with IT people who like to work at their desks rather than having to head down to the server room every time a small change is required.
It also allows multiple sessions on the client PC to be initiated, so you can work with a selection of computers at the same time - ideal if you're making synchronised changes and want to check they're all exactly the same.
Microsoft has also recently released an RDP client for Android, allowing you to use your PC from an Android phone or tablet. It might not be an ideal setup, but the fact you can do it in a pinch is something worth noting.
And because it's an inclusive feature of Windows, that makes it free for those that have that OS.
As a regular user of this tool I've been impressed with how well it generally works, though by its very nature there are some limitations that can't easily be worked around. Obviously it isn't much use for gaming or even CAD, and you also can't use it to make BIOS modifications, because Windows must be running.
There are also other software solutions that work in a slicker fashion, which might be worth considering.
Software KVMs
RPC isn't unique, and anyone looking for software solutions to the problem of a single mouse and keyboard with many computers will find a wide selection of choices available.
Most of these avoid the biggest problem, that of screen switching, and instead concentrate on the input devices and making that work better.
That isn't the compromise it might sound, because having multiple screens is relatively common these days, and placing a PC on each one controlled by a single set of input devices has many desirable uses.
I've done a breakdown of some of the better known ones, and what's great about many of them is the way that they splice additional PCs into the Windows environment like they're part of one system.
By doing this, the operator no longer has to think about them individually, but instead can use them like he has a massively powerful and parallel system. It also allows games to be played on one screen while other functions are monitored on another, generally seamlessly. When multi-tasking was first vaunted, this is what most IT people imagined it would be like, but using software KVMs it really can be.
Some tools even allow combinations of OS, so you can have three screens all controlled by the same mouse and keyboard, but running Windows, OS X and Linux each.
When you include functionality like the ability to inherently copy files from one desktop to another and even share a clipboard, this can make it the ultimate computing environment.
The only place it generally falls down is when the screen is local, because the machine must be physically close enough for the cables to both reach the monitor. Of course, you can just use a method to send the display over the network - a challenge that isn't impossible to meet.
For many home users either RDP or software KVMs are the way to go, although many IT people still spend thousands on dedicated hardware to do essentially the same job.
Final Thoughts
I'll be honest and say that I've dumped my conventional KVM hardware after many years of using it. Why? Because the cabling was a small nightmare, and occasionally it would malfunction and lock me out of my work machine. That could be a real problem if I had documents open, as a simple reboot could have highly undesirable consequences. Ironically, the solution to that problem was to use Remote Desktop to shut the system down in a controlled fashion.
For about six months, I've handled running the test rig on its own screen and peripherals, even if it takes up inordinate amounts of desk space.
But I'm about ready to consider switching back, probably to a software based solution with an additional dedicated screen. That should give me the convenience of using only a single mouse and keyboard and allow me to run graphics applications. If it wasn't for the graphics apps, I'd probably stick with Remote Desktop, as it allows you to use the machine with a few well-documented restrictions.
Something slightly odd that I realised when I was working on this article is how those who make wireless mice and keyboards have never considered tweaking them to this purpose. Surely it should be possible to have a mouse and keyboard that could alternate between two or more dongles or, using Bluetooth, allows multiple pairing.
I'm not sure why this hasn't been explored, as it could be a neat selling point, especially for corporate use in server admin and presentations.
The future of the KVM might include that tech, but I also suspect that it will also be entirely software-based, especially when you consider some of the features that Microsoft has been hinting might be in Windows 10.
It's talked about a game streaming capability between machines that would allow a tablet to play a PC game and the Xbox One to play a PC title. If it can achieve these objectives, solving the rendering and lag problems along the way, then this concept will become one that most people understand, not exclusively technologists.
While the reality of these developments is far from clear currently, undoubtedly at some point PCs could become the critical component in gluing many computers and their peripherals together, thus making what hardware you log onto and where ultimately much less important.