linux-mips-fnet
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Re: m700-10 success

To: linux-mips@fnet.fr
Subject: Re: m700-10 success
From: Systemkennung Linux <linux@mailhost.uni-koblenz.de>
Date: Fri, 10 May 1996 12:32:50 +0200 (MET DST)
In-reply-to: <439.199605092033@gladsmuir.algor.co.uk> from "Dom Sweetman" at May 9, 96 09:33:17 pm
Hi,

> There are three groups of MIPS machines you're likely to meet up with:
> 
> o Workstations/computers from SGI and their "friends" Pyramid and
>   Siemens-Nixdorf.  All big-endian, probably not adaptable.  SGI's
>   success means that this is much the largest group of machines.

At least the SNI RM200 is adaptable.  Changing is a option in the firmware.
If you stop the process of reprogramming the EEPROM you have to replace it
physically; the process also takes about 5 minutes and involves fiddling
with floppies.  So this is not an option for Linux :-(

> o DECstations and Sony workstations.  All little-endian, probably not
>   adaptable. 

Add Acer PICA to this list.

> o PC's built during the great Windows/NT-on-MIPS scam.  All
>   little-endian, usually not adaptable.  But very, very cheap.

Deskstation Type, Deskstation rPC44.  Not adaptable because based on a
chipset for Intel PCs.

> [Advertisement mode on: I've never met a MIPS board which can work
>  either way around, except the ones Algorithmics make.]

Admited, the description of your boards look nice!

> Where should Linux be?  LE is more like a x86, so will cause less
> porting trouble.  BE is more like SGI, but if you're planning on
> running SGI binaries there's an awful lot of work to do - starting
> with Unix SVR4-style shared libraries and running up through the SGI
> 3D graphics system.  If you're not planning to run SGI binaries, who
> cares?

The bad thing is that the MIPS ABI to which IRIX5 is relativly close is
big endian.  This cuts the little endian machine off from the supply
with shrink wrapped software for MIPS systems.

> Doing only LE would rule out an SGI port; doing only BE means those of
> you with Pica's and Deskstation PCs will need to throw them away.
> Better stick with both.

If you look through the code you'll find that there is quite some extra
code for support of bigendian machines.

> In practice, the software job of emulating enough of the Ultrix system
> call interface over SystemV was too big for MIPS - the idea was a
> symptom of the megalomania which ultimately led the company to the
> edge of bankruptcy (and into SGI's, fortunately friendly, arms).

Look through the system call table of Linux/MIPS and you'll find "similarities"
with Mips' RISC/os and the IRIX extensions.  The hooks are there but of
course not all implemented.

> As for emulating Ultrix over Linux, or MIPS/ABI over Linux... sounds
> pretty yukky to me.  But with lots of effort it might let you build LE
> and BE Linux kernels, but run the same binaries on both.  Any heroes
> out there?

I've already run big endian software on my "home edition of Linux/MIPS".
It works but of course only with pretty trivial software - my program was
assembler written "Bye, bye world!" program.

    Ralf

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