Sunday, September 4, 2016

Northgate Omnikey 101 vs. IBM Model M Keyboard

I have had the privilege of being lent a Northgate Omnikey 101 keyboard.  This keyboard is identical to the layout of my IBM Model M keyboards.  I am going to first identify the features of each keyboard and then give my impressions of the Northgate compared to the Model M.


Model M's use PBT plastic on the top and bottom enclosures, on the key caps and the key stems.  For this reason Model M do not yellow through exposure to ultraviolet light.  On the other hand, PBT can be somewhat brittle and it is not a rare thing to see cracked keycaps on a Model M.  Because keycaps come off very easily, it is often the case that you will find a keyboard for sale with one or more missing.  The enclosure is held together with hex screws requiring a long-barreled 7/32" driver to access.  Later Model Ms, mostly made by Lexmark and Unicomp, often have drainage holes cut into the bottom half of the enclosure for liquid spills, but the IBM-made keyboards rarely have them.

Northgates use a top shell and keys made of ABS plastic.  It is typically the case that you will find an Omnikey in a yellowed state.  Yellowed ABS plastic can become brittle, but there is no thin plastic on the Northgate keyboard, unlike the thin IBM keycaps.  The wear on the ABS keycaps will show itself as shiny areas, but the keyboard I have only shows this noticeably on with the Enter key.  The bottom half of the enclosure is made of metal.  The enclosure is held together with standard Phillips screws.

Keyboard Matrix

A Model M has a plastic top half (usually black, sometimes light gray) and a bottom metal half.  Sandwiched in between the plastic and metal layers is three layers of a plastic membrane.  The top and bottom layer have the pathways for an electrical circuit.  The plastic, when pressed together by the key press, makes an electrical contact.

The plastic, membrane and metal is held together by plastic rivets from the top half that are melted through holes in the membrane and form a button on the underside of the metal plate.  The rivets can be dislodged by time or by dropping the keyboard.  When cleaning a Model M for the first time, it is not uncommon to see several broken off rivets.  Some Model M enthusiasts have modded or repaired their keyboard by drilling out the rivets and replaced them with screws and nuts.

The Northgate has all its keys soldered onto a single-layer PCB.   In between the keys and the PCB is a metal plate.  Metal plates often have rust spots from spilled liquids or ambient humidity.  The plate & PCB is held together by screws, the keyswitch housing and solder.  Each key has a diode to allow for n-key rollover.


The Model M uses dye sublimated printing on all its keycaps.  Dye sublimated keys can fade somewhat by exposure to the sun, but I have not seen any on my keyboards.  The numberpad Enter and + keys will have stabilizers in the earlier keyboards, but these may not be present in the later keyboards.  Because the keycaps are often detachable from the keystem, it is easier to convert a Model M from a QWERTY to an Dvorak layout physically.

The Northgate uses double-shot injected molded keys.  The front of the Print Screen and Pause keys are also dye sublimated on the front face of the key.  Double shot keys will not fade by exposure to the sun, but because the keys are made from ABS plastic, they can yellow.  You can expect stabilizers for the Shift, Enter, the Backspace and large + and 0/Ins keys. Stabilizers on these keys are held by thin plastic and sometimes break when removed.  I have noticed that some of my IBM Model Ms have a spot on the right edge of the right shift key which makes it hard to press the key if you land on that spot, the Northgate does not have this hard spot, probably because of the stabilizer.

Pulling keys from the Northgate is not advisable to do frequently, the plastic stem in the Alps keyswitch can break if too much force is applied sideways.  I have read the same caution about modern keyboards which use Cherry keyswitches, which are a spiritual successor to the ALPS switches used in the Northgate.


Certain IBM Model Ms come with a detachable keyboard cable.  These Model Ms typically use an 6-pin Shielded Data Link connector, which looks like a large telephone connector.  These cables come in 5-pin DIN (black) and 6-pin mini-DIN (gray) varieties and are typically coiled.  Model Ms without a detachable keyboard usually use a 6-pin mini-DIN cable.

IBM Model Ms can require up to 275mA from a keyboard or PS/2 port.

The Northgates have a 6-pin mini-DIN cable on the back of their keyboard.  You can use a male-to-male 6-pin mini DIN to 5-pin DIN cable or a male-to-male 6-pin mini DIN to 6-pin mini DIN cable.  The official cable is also coiled and uses a right angle connector at the keyboard end.

Northgates can require up to 200mA from a keyboard or PS/2 port.

Both keyboards can use long cables.


The IBM Model M keyboard is compatible with all AT-class systems and many XT class systems.  An IBM PC/XT or Portable with the final BIOS will have no trouble with a Model M, but the IBM PC Model 5150 may or may not work with a particular Model M.  Late model Tandy 1000s will work very well with the Model M, but you can forget it when it comes to the earlier Tandys.  The status LEDs will not work in a computer that only supports an XT keyboard interface.

The Northgate is the king of compatibility when it comes to keyboards.  It works with IBM PCs, XTs, ATs and all compatibles.  With the appropriate adapter cable, it can work with Amstrad PCs (Ultra models only), Tandy 1000 SX & TX, Amiga 2000 and 2500 and AT&T WGS, 6300 and 6300 Plus.  The status LEDs will work in a XT keyboard, but may go out of sync at times.  You can reset the sync using the instructions in the Northgate manual.

Key Rollover (NKRO)

IBM Model Ms have a two key rollover.  Pushing three or more keys at once risks losing keypresses.
Northgates have true n-key rollover.  They will never drop keystrokes because multiple keys were pressed at the same time.  Many gamers prefer a linear switch without a click or a bump, and therefore would not want to use either keyboard.

Key Contact Technology

IBM's Model M uses buckling springs.  These are clicky and tactile.  It requires about 70g of force to actuate a key.

Northgate uses the Alps SKCM White or Blue switches.  These are clicky and tactile switches.  It requires about 75g of force to actuate a key.

Hardware Programmability

IBM Model Ms have no dipswitches or other user-settable options, everything is done in software, even XT/AT autoswitching.

Northgate keyboards are highly programmable.  All of them have 8 dipswitches to control the type of computer the keyboard is connected to, to swap the positions of the Caps Lock and left Ctrl key, to swap the \ and * keys (non-101s) to select the Dvorak layout and to activate sticky keys.  There is further programmability by using key combinations for key repeat and delay and validation time.


IBM Model Ms are easy to clean.  You can remove keycaps and keysteps easily with a small flat-bladed screwdriver or even a butter knife.  IBM Model Ms have the keyboard controller on a separate PCB connected via easily-detachable ribbon cables.  Unicomp (and probably Lexmark) Model Ms use a cheaper method that requires the keyboard controller to have direct contact with the membrane contacts and is held together by a small plastic clip.  If that plastic clip breaks, the PCB will lose contact with the membrane contacts.

Northgates are not so easy to clean.  The keys will come off only with great force and you may be concerned that you may break the key or the switch trying to pull the key off.  The keyboard controller is on the PCB with the keyboard matrix, so you cannot run it under water like an IBM Model M.

Impressions of the Northgate Omnikey 101

I really liked the Northgate and will regret having to give it back.  I love the fact that it will work or can be made to work easily with every PC I own except for the PCjr.  The IBM PC Model 5150, the IBM PC XT, all my Tandy 1000s, my 486, my Pentium III and my Core i7 Windows 10 computer all work with it.  My only quibble is for the Windows 10 machine.  The default repeat rate was way too fast for the Northgate, so I had to turn it down in the Keyboard settings in the Control Panel.  Microsoft makes the old-style Control Panel settings (the really useful ones) a bit harder to find in every new version of Windows.

I could see myself using the Northgate for my daily keyboard needs.  The keyboard layout between the IBM and the Northgate 101 I have  is identical, so the only thing I would need to adjust to is the keyswitch technology.  There are other variations of the Northgate, and the Omnikey Ultra T is very close to my idea of the ultimate productivity keyboard.  (I'd cut out the fat Enter key and restore the \ to it's usual place and add the Windows key, but that is it).

The Northgate is as about a perfect alternative for computers that do not work well or at all with IBM Model Ms.  The Northgate works perfectly with my Tandy 1000 TL whereas my Model M will fail to register the first keystroke on bootup correctly.  The Northgate feels far superior to the Tandy Enhanced Keyboard, which also works with just about everything.  The Northgate, however, will work in the Tandy 1000s with a simple passive adapter whereas ironically the Tandy Enhanched Keyboard will not.  The Northgate will also work perfectly with an IBM PC Model 5150.    I cannot get any of my Model Ms to work correctly with that computer.  (So much irony at work in this paragraph!)


  1. It's worth noting, by the way, that the Cherry MX switch and the Alps SKCL/SKCM switch both date back to 1983 - it's just that Cherry was AFAIK more expensive, and wasn't widely adopted until after Alps stopped production of their keyboard switches (including the cost-reduced SKBL/SKBM.

    As far as removing caps, the Cherry MX switches hold onto caps MUCH less strongly than an Alps SKCL/SKCM/SKBL/SKBM switch. I've actually managed to pull an SKCM switch apart trying to remove a keycap, and that was with directly pulling up on the keycap.

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  3. Nice thorough comparison. I actually appreciate my Model M better now, though I still would like a proper nkro gaming keyboard.

  4. Thank you for the great comparison. As a multi-decade model M user with the opportunity to get a Northgate, I was debating it. Your article helped make my decision. :) Thank you again.

  5. King of compatibility? You understate it. I retired yesterday; I will probably sell the 101 that I have used daily for the past 30-some years on eBay. I used a DIN to PS2 adaptor, and then a few years ago bought a PS2 to USB adaptor, and it still works like a charm.

    1. I have found that a Soarer's converter makes my IBM Model M work like a charm with my 2021 PS2-less machine.

  6. I've been using my Northgate for over 30 years now, and the only maintenance has been pulling the keys for a thorough cleaning (about 8-10 years). The keys go in a basin with soapy water -- dish soap or laundry detergent -- for a few hours, and as walk by it I stir the water up a little. After a few hours they come out spotless, and go onto a towel to dry overnight. The metal base gets a cleaning with alcohol and Q-tips, while the plastic cover gets a scrubbing with alcohol and paper towels. Just did it. Good for more years. Love my Northgate!