Psion MC 400 Mobile Computer

Psion MC 400

Probably in my top five of most wanted retro machines I’ve finally acquired a Psion MC 400 mobile computer.  Originally released back in 1989 this ill-fated machine, described by Time Magazine in their All Time 100 Gadgets as one of five gadgets ahead of their time, was initially priced in the UK at £845.00 and according to some sources sold less than a thousand units.

MC 400 Touchpad

Psion MC 400 Touchpad

It is therefore unsurprisingly quite rare.  Way ahead of its time it featured the first touchpad, removable storage in the form of sold state disks (SSDs) and a claimed battery life from 8 AA alkaline batteries of 60 hours.

Lack of compatibility, proprietory interfaces and a high price no doubt all contributed to its lack of success but you have to admire the manner in which its designers and engineers pushed the boundaries to create a gorgeous product that is reminiscent of what Apple do so well.

Parallel & Serial Port Module

The Psion is powered by an Intel 80C86 processor and has 256 Kb of memory.  For external connectivity there’s a standard parallel port, a 9 pin mini DIN RS232 port and Psion’s fast serial link, a precursor if you like to USB.  The parallel and RS232 ports are contained within a removable module that slides into one of the two identical sockets found on the rear of the machine.  Other modules including a modem were available, my MC 400 has a dummy module in the second socket.

Socket & SSD

There are four sockets for SSDs, two on either side of the machine and these are compatible with the SSDs used in the Series 3.  The touchpad mimics the screen, so the position of your finger on the pad will correspond with the cursor position on the screen and the whole pad is clickable.  In practise it doesn’t work particularly well, needing a lot more pressure to move the cursor than we’ve grown accustomed to with modern machines and accuracy is poor.  Fortunately, navigating the GUI with the keyboard is pretty efficient once you’ve learnt the required key combinations.

LCD Display

The screen is a non-backlit retardation film LCD with a 640 x 400 resolution.  It’s crisp but needs careful positioning of lighting for optimal viewing.  The contrast can be adjusted by way of a dedicated function key found to the right side of the touchpad.

The MC400 runs the Psion developed EPOC graphical operating system, a preemptive multitasking OS which would in later years evolve into the Symbian OS adopted by Nokia for its early smartphones.

Battery Module

A suite of software applications are supplied on SSD, a text editor, diary, personal database, calculator, file manager, terminal emulator and word processor.  Not a great deal of other software was available as far as I can tell although my MC 400 did come with an additional spreadsheet on SSD.

Solid State Disks

There were two NiCad battery packs available or you can use 8 standard AA type alkaline batteries which reportedly give an extraordinary 60 hours plus of usage.  I’m currently using rechargeable Duracell AA’s and will be interested to see how long they last.

The included Link software can be used in conjunction with Psion’s PsiWin software (available here) and a suitable cable to transfer data backwards and forwards between the Psion and a PC via the RS232 interface.  I was concerned it would be difficult to locate or build a suitable cable for the non-standard 9 pin mini DIN but discovered here that you can use a Series S3/S3A’s lead.

Rear View

I plan therefore to acquire one of these cables and see if I can get PsiWin working and also if I can hook up a modem.  I’m also going to look at doing some programming with OPL, Psion’s structured programming language.

Some useful resources:-

Excellent MC 400 info and screenshots

More general information

Another good MC 400 resource

Useful hints and tips.

39 thoughts on “Psion MC 400 Mobile Computer

  1. Wow! Very nice!
    I too have always dreamed of having one of these, from the moment I saw the flyer when they were released back in the day. I’ve been keeping my eye out for one but they are pretty rare! Congratulations on your catch – I’m jealous 🙂
    I remember programming a simple bank account program on a Psion II, the OPL was quite easy – a light grasp of BASIC and you are there!


  2. Cheers Smuggsy, they really are very nice machines, I’m really chuffed with it. As you say OPL looks pretty straightforward although from what I’ve read the MC 400 has a rather limited implementation. Looking forward to playing some more.



  3. Thanks Rob, I saw those when I was researching the MC 400 before I bought it, they’re very helpful. Do you know of any other software available for the MC 400?


    1. I stated on the screen-shot site that no SDK was ever released for the MC 400 but this is not entirely true. Psion made available a PC (Dos) based C SDK for the Series 3 that was backward compatible with the MC 400 but by then it was to late. This SDK was very expensive and involved a steep learning curve even for experienced C programmers (I stuck with OPL). I also stated that no third party software was ever released for the MC 400 but recently came across this page It has a Missile Command game for the MC 400 though I have not tried it myself. The undocumented key combo for screen captures on the MC is the same as the Series 3 (can’t remember right now). I copied the .pic files to the pc and converted to png using a free program called xnview. Feel free to use these images on your own site.


  4. I have a used MC400 complete with programing manual for sale. I also have all/most of the options that were available at the time. I’ve had from new and all the updates i.e. ribbon were implemeted at Psion in Greenford UK. I want it to go to a good home.


      1. Hi Aliennerd

        I have the spell checker, Spreadsheet, Programming manual, Spreadsheet manual, spell checker manual, word processor manual, Mini link software (floppys) for both Mac and PC with relevant leads, 1 off 512K Ram SSD, 1 off 128K Ram SSD and 1 off 128K Flash SSD, AC adaptor, 2 off battery cases(AA). This computer has the larger system disk(256K flash) containing the Word processor. Its quite an innovative computer for its time and to date I’ve not come across a better laptop keyboard. I paid around £900 at the time when I bought it and I have no idea what its worth now. I’ve been using Psion computers since their inception and I even have a 1 line (original) organiser. I just want to know they’ll end up with people who appreciate good and innovative design. I forgot to say my unit still works completely.


      2. Sounds as though you have a lovely system there John. I’d certainly be interested in it but as I already have one and I know Smuggsy has been after one for a while perhaps get in contact with him and let me know how you get on.


  5. Hello,

    I too have an mc 400 for sale.
    Mine has seen better days, the battery pack has broken open and some corrosion is setting in. Also it’s a bit dusty, i don’t know if it turns on as i don’t have an ac adaptor.
    I just put it on Ebay today then found this page.
    This is it’s number on ebay; #160808451041
    Sorry, i would have offered it to you guys if i’d known.
    Even if you don’t want it could you tell me how much it’s likely to be worth please.




  6. Hi Nick, difficult to say what it’s worth given that you can’t test if it’s working or not. Nice condition, working models have gone for £70 – £100 over the last few months so I would imagine you’d be looking at a fair bit less than that unless you can show that it does in fact work.


  7. These are amzing machines, I use mine daily (more than my iPad!). I have recently completed my dissertation on it and run my eBay business on it with an OPL program I wrote. It was a tricky to set up but now I have the printer configured it prints directly to my Brother laser and is interfaced to my XP 2 home system for backup etc. And yes they run for about 50 hours on a set of standard AA’s!!


  8. Wow, that’s seriously cool, would love to see some pictures! They seem to be appreciating rapidly in value, one just went for £290. Unbelievable, that’s three times what I paid for mine only a few months ago.


    1. I want to bid, but you only accept bids from the UK, why miss out on buyers from the vast majority of the world ?? It’s not hard to ship international and I’m happy to pay the extra shipping so there is no extra cost to you.


    2. Have you guys done and offline deal? The item seem’s to have ended and I was eagerly watching it 😦
      Or has it been sold elsewhere? about to be relisted?


  9. Hi guys i just stuck my mc400 on ebay , i tried powering it up via battery pack but could not find on/off power switch , and i dont have a power supply , so its on as spares / repairs , its got 2 ssd with it and spreadsheet theres the item number if anyones interested 271247226282 thanks


  10. Hi, i`ve just been clearing out a house to renovate and found a boxed mc400, looks as if it`s brand new in box with power cable etc. No use to me as i`m not really that interested in computers so if any of you guys want to buy one get in touch. Joe- 07870286814 north lancs.


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