25aa5b8459
- isa => nexus - flags - GPL_MATH_EMULATE - document breakage of non-GPL emulator since we use new compiler. - break lines in paragraohs I touched so that sentenses start on new lines.
93 lines
3.7 KiB
Groff
93 lines
3.7 KiB
Groff
.\"
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.\" Copyright (c) 1993 Christopher G. Demetriou
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Christopher G. Demetriou.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software withough specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" from: npx.4,v 1.1 1993/08/06 10:58:03 cgd Exp
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.\" $FreeBSD$
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.\"
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.Dd August 28, 1993
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.Dt NPX 4 i386
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.Os FreeBSD
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.Sh NAME
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.Nm npx
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.Nd Numeric Processing Extension coprocessor and emulator
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.Sh SYNOPSIS
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.Cd "device npx0 at nexus? port IO_NPX flags 0x0 irq 13"
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.Cd "options MATH_EMULATE"
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.Cd "options GPL_MATH_EMULATE"
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.\" XXX this is awful hackery to get it to work right... -- cgd
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.\" What the heck does he mean? - cracauer
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.Sh DESCRIPTION
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The
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.Nm npx
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driver enables the use of the system's Numeric Processing Extension
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coprocessor,
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if one is present. Numeric processing extensions are present in
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systems with
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.Sy 486DX
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CPUs and in systems with
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.Sy 387
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or
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.Sy 487SX
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coprocessors. The
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.Nm npx
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driver is required for proper system functioning regardless
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of whether or not a NPX is present.
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.Pp
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If there is no NPX present in the system, the "MATH_EMULATE" or
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"GPL_MATH_EMULATE" option must be defined in the kernel configuration
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file.
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It will provide support for the instructions normally executed by the
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NPX.
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If there is no NPX in the system and the kernel is not built with math
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emulation, the system will not boot.
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.Pp
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For a description of the possible "flags" values see the LINT kernel
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configuration file.
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.Sh CAVEATS
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The emulator is much slower than the NPX coprocessor.
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This will result in poor floating-point math performance
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if the emulator must be used.
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.Pp
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The non-GPL emulator does not support the whole set of npx
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instructions.
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It is sufficient for booting and configuring a system, but it cannot
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support a system with normal workload unless care is taken to compile
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the whole system (including third-party packages) with compiler
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options that avoid the use of the non-emulated instructions.
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.Sh BUGS
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There are lots of them, especially on old cheap motherboards.
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In particular, some motherboards do not have the interrupt lines from
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the NPX to the CPU wired properly.
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If this is the case, the emulator must be used if consistent system
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operation is desired.
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.Pp
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Emulation of the transcendental functions instructions in the non-GPL
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emulator is incorrect.
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Emulation of other instructions is suspect.
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