----Next_Part(Mon_Mar_17_11:03:49_1997)--
Content-Type: Text/Plain; charset=us-ascii

On Fri, 14 Mar 1997 11:33:48 -0800,
hotz@jpl.nasa.gov (Henry B. Hotz) wrote:
> I got the impression from the SoftwareFPU doc's that it was only the first
> released version of the chip that had the problem and that Motorola had
> acknowledged it and would replace it if you could find your way through
> channels.

Really?  The attached is more or less the doc that came with the
latest release of SoftwareFPU, and I didn't notice anything like
this... (I extracted ASCII characters contained in the distributed
Word document using GNU Emacs, so there may be some typos).

> Perhaps I'm reading too much into what they said, but it's
> basically the same kind of situation as the famous Pentium FPU bug.

I'd say much better than that *in*famous Pentium FDIV bug, though.
Motorola disclosed the bug information without waiting for some poor
user to find it ;-)

> I'm not opposed to software workarounds, but I don't think they should
> clutter up the main distribution.

I agree, yet we could make the mac68k (or all m68k) distribution like
that of the i386 port: the default libm not using i387 (FPU)
instructions.  I suggest it because it's *much* easier to implement
only reliable FADD, FSUB, FMUL and FDIV instructions in FPE and have
libm do the rest, than to implement everything in FPE.  It is very
hard to write a reliable numerical function.  That's why we have a
4-credit full semester numerical analysis class in computer science
department ;-)

Those who have FPU in their system can compile their own libm which
uses FP instructions, or we could distribute a separate libm binary
file for full-68040/6888[12] owners.

As I recall, I once suggested this on port-m68k but I didn't get many
replies, probably because of my poor expressions.

> I would rather that people figure out
> how to get someone to fix the problem properly by replacing the chip.  Then
> we document the chip rev levels and who to contact for the replacement.  I
> hope I'm not being too idealistic here.

I don't think you are.  I'd say those who have the broken LC040 should
go get a full 040 ;-)  Remember, the broken LC040 cannot properly
handle f-line traps, preventing any software FPU emulator from
properly functioning.

As for actual upgrade, John Neil and Associates (the firm which offers
SoftwareFPU) offers upgrades (even for the PowerBooks), for example.

Cheers,

Ken

----Next_Part(Mon_Mar_17_11:03:49_1997)--
Content-Type: Text/Plain; charset=us-ascii

68LC040 CPU Bug Information
John Neil
April 23, 1996

68LC040 CPU Chip Bug

The 68LC040 CPU chip has a bug in it which prevents many FPU
applications from working properly with SoftwareFPU.  The bug is
confirmed by Motorola and listed as bug E4 on revision 4 of the
official Motorola 68LC040 errata sheet.  Unfortunately there is no way
for SoftwareFPU to work around this bug.  If you have SoftwareFPU
installed on a 68LC040 Macintosh, you will have to test each FPU
application you use to see whether it will work on your Macintosh.  If
the application crashes, it is probably due to the 68LC040 CPU chip
bug.  To verify the cause of the ecrash, test the same application on
a regular 68040 Macintosh.  If the application operates correctly Uon
a 68040 Macintosh, the CPU bug is causing the application to crash on
your 68LC040 Macintosh.  If the application crashes on a 68040
Macintosh, the CPU bug is not the cause of the 68LC040 crash.  UIf
your FPU application crashes with SoftwareFPU because of the 68LC040
CPU bug, your options are 1) Replace the application with a version
that does not require an FPU, if available. 2) Replace the 68LC040 CPU
in your Macintosh with a 68040 CPU that contains a hardware FPU.

John Neil Associates sells 68040 upgrades for desktop Macintoshes and
PowerBooks.  WSee the price list at the end of the About SoftwareFPU
document for more information.

 Install a PowerPC upgrade card in your computer.  FPU applications
work properly with SoftwareFPU on PowerPC Macintoshes.

----Next_Part(Mon_Mar_17_11:03:49_1997)----