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Re: r3000 instruction set

To: "Kevin D. Kissell" <>
Subject: Re: r3000 instruction set
From: "Steven J. Hill" <>
Date: Sun, 22 Feb 2004 22:03:17 -0500
Cc: Eric Christopher <>, Mark and Janice Juszczec <>,
In-reply-to: <001001c3f98e$2270dcc0$10eca8c0@grendel>
Original-recipient: rfc822;
References: <> <> <001001c3f98e$2270dcc0$10eca8c0@grendel>
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040122 Debian/1.6-1
Kevin D. Kissell wrote:

The 3900 family should run MIPS I code compiled for the R3000.


The 3912 has no FPU, but if you're running on any contemporary
MIPS/Linux kernel and library system, you neither need nor want
soft-float.  The kernel does FP instruction emulation.  Running soft-float
would make for faster, if larger, code, but requires that the whole
system, particularly glibc, be built for soft-float, which is rarely done
(and the last time I tried it, didin't quite work with the standard
glibc sources out-of-the-box).
Correct. I use the FP emulator in Linux for my TX3917/PR31700 stuff. I
have had no problems. Current glibc has assembly code that assumes hardware
floating point which is why building for soft-float does not work out of
the box. There are probably some patches out there to rectify that. My
personal choice, use uClibc ( for your C runtime. I wrote
the dynamic linker loader for MIPS and would highly recommend you try it out.
I would really like to see more testing of it.

Also, I have some documents for the 3912 on my FTP site:

It should be noted that the Toshiba TX3912 and the Philips PR31700 are
identical cores. There was definitely some cross-licensing going on there.
Perhaps Kevin or Dominic would know this in more detail, but it is not
really that important.


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