DECstation 2100 floating point

[George Harvey <fr30%dial.pipex.com@localhost>]

Hi,

I've been giving 5.1 a try on my DECstation 2100 (PMIN, R2000 CPU). I
had a bit of trouble finding a disk that the ROM would boot from but
apart from that, the network install ran smoothly. However, running a
few test programs, I'm seeing a lot of floating point errors. For
example, the 'flops' benchmark from pkgsrc returns mostly 'nan' and
'inf' values (see sample output below). If I run the same tests on my
5000/133 (3MIN, R3000 CPU), then they work normally so I'm wondering
what the difference is between R2000 and R3000 floating point behaviour?

For info, dmesg shows the CPU types as follows:

On the 2100 it incorrectly shows the CPU as a R3000:
cpu0 at mainbus0: MIPS R3000 CPU (0x220) Rev. 2.0 with MIPS R3010 FPC
Rev. 2.0
On the 5000/133 it shows:
cpu0 at mainbus0: MIPS R3000A CPU (0x230) Rev. 3.0 with MIPS R3010 FPC
Rev. 4.0

George

=== 'flops' output on DECstation 2100 ===
   FLOPS C Program (Double Precision), V2.0 18 Dec 1992

   Module     Error        RunTime      MFLOPS
                            (usec)
     1             nan     76.7969      0.1823
     2     -1.4667e+01      0.0000         inf
     3             inf -719077252129430822595458597950846748799629
130127667406135614065924966910426536007118954834557502031540308274
024000458672866887843129056069389197470953087699454232971665626483
163798647964987849155232846343667122095319825962132090969358849540
2929750866960090586776981335080164582762972091727297738377789
44.0000 -0.0000
     4             inf      0.0000         inf
     5             inf      0.0000         inf
     6             inf      0.0000         inf
     7             nan      0.0000         inf
     8             inf      0.0000         inf

   Iterations      =          0
   NullTime (usec) =     8.0000
   MFLOPS(1)       =    -0.0000
   MFLOPS(2)       =    -0.0000
   MFLOPS(3)       =    -0.0000
   MFLOPS(4)       =    -0.0000

=== end ===