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From: umapd51@cc.ic.ac.uk (W.A.C. Mier-Jedrzejowicz)
Newsgroups: comp.sys.handhelds
Subject: Re: Soldered-in ROMs: 20/20 hindsight
Summary: Plug-in OS is a good idea - HP tried it
Keywords: HP48SX, HP-71B, Operating System updates
Message-ID: <1991Mar14.052551.5048@cc.ic.ac.uk>
Date: 14 Mar 91 05:25:51 GMT
References: <9CA71B286000016D@gacvx2.gac.edu> <27d3cedf:2298.1comp.sys.handhelds;1@hpcvbbs.UUCP>
Sender: Wlodek A.C. Mier-Jedrzejowicz
Organization: Imperial College Computer Centre
Lines: 18
Nntp-Posting-Host: suni1cc


Kevin Jessup suggests the HP48SX operating system could have been on a
plug-in card, and ends with "Bad idea, right HP?"
Well, in fact, it's such a good idea that HP tried it with the HP-71B
(the first HP handheld with the Saturn CPU which is now in the HP28 and
HP48 etc). On the HP-71B you could plug in an alternative operating
system on a plug-in module in port 1 (of 4 - how I wish they'd managed 4
in the 48 !) - the module needed an extra long connector on one pin to
disable the OS inside the 71.
The CMT MCII and CMT MCV also have the system ROM accessible from the
outside.
The problem with this method is that if you drop the handheld, any OS
module which is plugged-in, not soldered in, might fall out! This is
likely to be more of a problem in the wide world out there than perhaps
we realise while discussing bugs on comp.sys.handhelds.
Regards,
Wlodek Mier-Jedrzejowicz, Space & Atmospheric Physics, Imperial College,
London