Psion 3c

The finest miniature 8 bit computers of their time

Upgrading the Psion 3a.

Announced on 5th September 1996, for USA release in October. This takes the chassis of a Psion 3a and makes incremental improvements to the SIBO range. Personally, I think this is probably a good move - who wants to buy the early model of a new computer, with all the bugs that implies?

You may also note the earlier Psion 3a, and the replacement Psion 5 Epoc series.

Hardware changes

I always think a bit more ram would be nice, especially when I filled my existing model. This model does not increase the maximum available ram at all, which I think is an error with so much shareware available now. I notice much interest in HP200LX upgrades to 5 Mb, and that a 4 MB model is available as standard, which indicates some level of demand in palmtop systems. I could certainly easily fill several megabytes with data files, especially if I were to do my web site updating on the Psion (which would be a very convenient method of adding minor changes).

The 57.6k Baud RS232 serial port is most welcome, as is the smaller cable. The soap on a rope cord serial cord needed by the 3a is a pain to carry. Unfortunately, the port does not use a standard connector, so you still have to carry a Psion cord with you, negating a lot of the advantages of standard RS232. Just what is wrong with a 9 pin D connector (apart from size?) I hope someone makes a Psion to 9 pin converter, so we have only a small gadget to carry.

The IrDA is really good news, especially to someone like me who purposely got a HP 5MP printer with IrDA port, because I thought this sort of thing would eventually arrive. The one metre range is unfortunate, but certainly not unexpected. It works fine with my printer. Unfortunately, it doesn't appear to work with other brands of computer without some programming intervention.

The backlite makes the screen significantly less clear normally, so that it is now no better than the display on the Sharp PC3000 or Lexicomp. However, every now and then you just don't have sufficient light to see your display, and the backlight solves that problem. The impact on battery life is considerable, with the backlight drawing about four times what the rest of the Psion draws (I believe Psion claim equal power drain from the backlight and the rest).

Software changes

A bunch of things I mumbled about (or looked for ways around) have been addressed. The data finally has sorting, and a list view of multiple items. Agenda finally has a month view. A handy jotter for taking quick notes for later processing. Sound recording easier. It is a nice range of improvements. You can find shareware to add most of these to the older 3a, so it is the RS232 and IrDA that are most important.

Please note that the Psion Epoc software described on this site does not work with the earlier Psion SIBO designs. The only page I have relating to Psion SIBO programs is not being maintained nor updated (except when authors send me corrections).


More connectivity in general. The new model is however not compatible with 3Fax, 3Link, or 3a Parallel Printer cable.


The 1 MB 3c was A$895, while the equivalent 3a has dropped to A$795. The 2 MB 3c is A$995, the 3a is $895, all prices including the very steep (22%) Australian wholesale sales tax. For comparison, the US price of a 2 MB 3c is US$599, and in California taxes raise that to US$650.70 or A$811. Bit of a difference there, so if you are travelling, an overseas buy may be an idea. Prices were correct November 1996. Prices dropped considerably when the Psion 5 appeared in June 1997 - surprise. And of course these old models are no longer made.

As at February 1997, the price for a Psion 3c in the USA was down to US$450, however most stores had not revised prices on older models, so take care when buying.

Flash memory in Australia is A$125 for 128k (US$55.25), A$330 for 1 MB (US$165.75), while RAM is A$160 for 128k (US$85), a$360 for 512k (US$191.25) and A$680 for 1 MB (US$356). US prices are from New World Technology. An external SSD drive is A$945. There is a way of faking up an external SSD drive for about A$50 instead, and it works fine.

Serial Port

The Psion serial port connectors are as below, but there is a suggestion the voltage swing is 5 volt only, not 12 volt.

 1      15
 PS232 (9 pin)  (Psion)
 1               nc
 2               12
 3                8
 4               11
 5                1
 6               13
 7                9
 8               14
 9               10

IrDA connection

The IrDA port is asynchronous, as you would expect. The IrDA specification permits data transfer rates of 9600, 19200, 38400, 76800 and 115200 (and higher rates up to 1.152 Mbit), with 115200 the maximum speed supported by the 3c. After protocol delays and turn around time, the actual data rate will be somewhat lower. Presumably the Psion will negotiate transfer rates, starting at 9600.

Psion have not mentioned how to access the IrDA port from the OPL language. As IR controls for TV and video work at about 40kHz, it seems unlikely the Psion can be used to control them.

Jim Pollack has been running the IrDA port at 19,200 baud, which with start and stop bits transfers 15,360 data bits per second. CRC calculations take 17.3uS per byte. His ircopy routine can sent to the Psion at 115,200 baud, but he had to add delays to avoid overrunning the Psion, so his best rate was 57,600. The Psion IR transmitter is only good to 19,200 baud. He adds the Psion is just connecting the IR to a UART. The only real restriction is that the transmit blinds the receive, so you can't run both at once. His web site is

Programs available include vbIRsave, which transfers Psion highlighted text to a MS Windows clipboard. irNFS bidirectional Psion PC. p3nfs for Unix and Atari access, supporting create, getattr, mkdir, read, readdir, remove, rename, rmdir, setattr, write, getdevs and statdev. irbackup.

Tim Wilde wrote an IR chat program, which was at

General notes

Certain 3a peripherals will not work with the 3c. The "soap on a rope" cable will not work. Neither will the printer cable, nor the 3Fax. All 3a application data will work on a 3c. Psion expect most 3a software to work on a 3c. Please note that Psion SIBO software does not work on the Epoc (Psion 5) range, nor does EPOC work on the Psion 3 range. The revised PsiWin cable and printer cable for the Psion 3c is identical to that used on the Psion 5 and more recent models.

Psion do not offer a 1 Mb to 2 Mb upgrade, so choose your model carefully.

This site will look much better in a browser that supports W3C web standards but it is accessible to any browser or internet device, including Psion Web and similar PDA or limited browsers. Netscape 4.x users - turn Style Sheets off. Your style sheet support is too broken to use (sorry). -> epoc -> epoc hardware -> psion3c

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