Serial interfaces (was Re: Any former Psion 5 owners out there?)

Liam Proven lproven at
Tue Jul 27 15:12:31 CDT 2010

On 26 July 2010 20:03, Tony Duell <ard at> wrote:
>> TBH, I don't know. I'm sure you're right, though. I improvised a
>> solution involving a couple of instances of DRIVER.SYS and DRIVPARM or
>> something like that to persuade DOS that a 1.4MB drive was actually a
>> 1.2MB drive, I think.
> In which case you may have onl;y 15 valid sectors on each track (1.2M
> format) not 18 (1.44M format). This could end up similar to the strange
> disk image that I received...

Oh dear.

> Mine started out as a challenge. As is well-known, I am forever moaning
> about lack of real service data -- schematics and the like -- for
> computer equipmetn. So, about 15 years ago I was set a challenge -- to
> make a machine capable of running linux but which was 100% docuemtented
> (not necessarily 'open' -- the scheamtics could be copyrighted, etc, but
> they had to be avaialble). I had to be able to get full schematics and
> source listings of all software involved (that included the ROM BIOS
> needed to boot linux -- the linux sources took care of that requirement
> for the OS).
> I didn;t maanage it -- because I couldn't get a scheamtic of the hard
> disk. But that was the only part I couldn't get. The guy swho set the
> challenge acknowledged that I'd certainly met the spirit of the
> requirements :-).

I am not so much impressed as awed.

>> I'm impressed that you managed not only to get such a thing running,
>> but to be using it still. For any kind of contemporary usage on the
>> 21st-century Web, it must be incredibly slow.
> It is slow. Very slow. And the video output is an origianl MDA text-only
> card and monitor (I have a CGA card in there too, X doesn't support that
> either, and I find text on the 5151 a lot easier to read than on any CGA
> monitor I've tried (I have the original 5153 and an NEC TTL RGB monitor
> that I modified to have RGBI inputs -- I did that before I amanged to
> obtain a 5153). So not much hope of accessing most web sites. But it runs
> gcc, it runs LaTeX, and things like that.
> To be honest, on the few occasions that I need to look at graphical web
> sites (mostly to read data sheets, technical manuials, etc) I go to an
> internet cafe.

Haver you considered getting one of those Chinese Godson2-powered
(MIPS-compatible) Linux laptops? It's what Richard Stallman uses now.
All open-source: the CPU, hardware, firmware & all software is Free
and open source.

Product page:

I don't know anyone directly selling it in the UK but very similar
devices are about, and they're cheap, too - under £150. Not
powerhouses - the Longson CPU is only about 400MHz - but I believe
they're pretty usable.

I think they are generally regarded as *the* most open modern computer
in the world, but I don't know if they'd be Duell-compatible.

Liam Proven • Profile & links:
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