Josh: Remove the Category:Home Computers link — the category has no page and renders as a red link

2026-09-09T10:50:39Z

Remove the Category:Home Computers link — the category has no page and renders as a red link

← Older revision		Revision as of 11:50, 9 September 2026
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	[[Category:Psion]]		[[Category:Psion]]
	~~[[Category:Home Computers]]~~

Josh: Create Psion page set: researched from Psion manuals, service documentation and community repair sources

2026-09-08T23:02:00Z

Create Psion page set: researched from Psion manuals, service documentation and community repair sources

New page

{{Infobox computer
| name = Psion Series 5mx Pro
| image = [[File:Psion Series 5mx Pro.jpg|250px]]
| caption = A Psion Series 5mx Pro
| developer = Psion PLC
| manufacturer = Psion PLC
| type = Clamshell palmtop / PDA
| release_date = 1999
| cpu = ARM710T core in Psion's custom "Windermere" SoC @ 36 MHz
| memory = '''No ROM.''' Sources quote 24 MB or 32 MB of RAM, part of it reserved to hold the OS image
| storage = Internal RAM disk; CompactFlash slot — '''also the boot device'''
| display = 640 × 240 touch-sensitive backlit LCD, 16 greyscales
| sound = Speaker and microphone, with a dictaphone function
| dimensions = 170 mm × 90 mm × 23 mm
| weight = 354 g including batteries
| os = EPOC (ER5), loaded from CompactFlash
| predecessor = [[Psion Series 5mx]]
| model = Shipped with a 16 MB CompactFlash card holding the operating system
}}
The '''Psion Series 5mx Pro''' is a rare variant of the [[Psion Series 5mx|Series 5mx]] that differs in one fundamental way: '''it has no ROM'''. The operating system is loaded into a reserved area of RAM from a '''CompactFlash card''', which makes it upgradeable in a way no other EPOC Psion is.<ref name="wp">[https://en.wikipedia.org/wiki/Psion_Series_5 "Psion Series 5"], Wikipedia. Source for the existence of the 5mx Pro and the statement that it differed only in having the operating system loaded into RAM and hence upgradeable.</ref>

Mechanically and electrically it is a 5mx. '''Everything in the [[Psion Series 5mx]] pages applies''' — the same Windermere SoC, the same 640 × 240 screen, the same sliding clamshell, the same screen ribbon and the same hinge hooks.

== How it boots ==

The Pro shipped with a '''16 MB CompactFlash card''' carrying the OS image. The file is called '''<code>Sys$rom.bin</code>''' and is about 10 MB.<ref name="wuffs">Ash Wolf (Ninji), [https://wuffs.org/blog/building-a-psion-emulator "\"16 Shades of Grey\" — Building a Psion/EPOC32 Emulator"], 27 December 2019. Source for the 5mx Pro's boot-from-CompactFlash arrangement, the <code>Sys$rom.bin</code> file name and size, its structure, and the difference from the standard 5mx.</ref><ref name="grp">Community discussion of the differences between the Psion 5mx and 5mx Pro, comp.sys.psion.misc. Source for the absence of ROM, the reserved RAM region, the 16 MB CompactFlash card supplied with the machine, and the boot-time prompt offering CompactFlash or a yModem serial load.</ref>

'''If the machine has no operating system available, it will not simply fail.''' On startup it asks whether to '''insert a CompactFlash card containing the SystemRom''', or to '''make a serial connection and load the system over a yModem transfer'''.<ref name="grp" />

'''That prompt is not a fault.''' It is the single most important thing to know about a 5mx Pro, because a Pro bought without its card looks like a dead or corrupted machine to anyone expecting a normal 5mx.

== How much RAM? ==

Sources disagree. '''24 MB''' and '''32 MB''' are both quoted for the Pro, and part of the RAM is reserved to hold the OS image rather than being available to the user — which is the likely explanation for the discrepancy, though no source states it in those terms.<ref name="grp" />

A standard 5mx has '''8 or 16 MB''' with the OS in ROM.<ref name="wp" />

== Why it exists ==

Because the OS is a file rather than a mask ROM, '''upgrading it is a matter of replacing that file'''.<ref name="grp" /> On a standard 5mx an OS change means a new ROM daughter board of the right build and language.

It also had an unintended benefit for preservation: because 5mx Pro machines load <code>Sys$rom.bin</code> from a card, '''copies of the 5mx OS image circulated in a form that could be studied''', and it is how the WindEmu emulator and the MAME <code>psion5</code> driver were developed without access to a ROM dumper.<ref name="wuffs" />

== Identifying one ==

* '''It boots from CompactFlash''', and says so if the card is missing.<ref name="grp" />
* The screen is often described as slightly '''brighter and crisper''' than a standard 5mx's.
* Otherwise it is externally a Series 5mx.

'''Note that a 5mx Pro screen assembly is interchangeable with a standard 5mx one''' — screens from any 5mx work on any 5mx — which makes Pro machines with dead boards a useful source of parts.

== General maintenance ==
{{Main|Psion Series 5mx Pro General Maintenance}}

== Troubleshooting ==
{{Main|Psion Series 5mx Pro Troubleshooting Guide}}

== Hinge and screen cable ==

The Pro uses the same chassis, hinge wires and screen ribbon as a standard 5mx. See '''[[Psion Series 5mx Hinge Repair]]'''.

== See also ==

* [[Psion Series 5mx]] · [[Psion Series 5]] · [[Psion Revo]]
* [[Psion Series 5 Service Manual]] — applies mechanically
* [[Battery Refurbishment]]

== References ==

<references />

{{Navbox-Psion}}

[[Category:Psion]]
[[Category:Home Computers]]

Psion Series 5mx Pro - Revision history

Josh: Remove the Category:Home Computers link — the category has no page and renders as a red link

Josh: Create Psion page set: researched from Psion manuals, service documentation and community repair sources