Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!alliant!spain From: spain@alliant.UUCP Newsgroups: comp.arch Subject: Re: How does compiled code use the floating point unit? Message-ID: <362@alliant.UUCP> Date: Wed, 10-Dec-86 01:44:29 EST Article-I.D.: alliant.362 Posted: Wed Dec 10 01:44:29 1986 Date-Received: Sun, 14-Dec-86 07:11:43 EST References: <394@houxs.UUCP> Reply-To: spain@alliant.UUCP (Dave Spain) Organization: Alliant Computer Systems, Littleton, MA Lines: 15 In article <394@houxs.UUCP> daw@houxs.UUCP (D.WOLVERTON) writes: > >In some systems, the hardware floating point (fp) unit is _optional_. >... > Are there other scenarios in use? I am familiar with one more mechanism, call it 3.5 which goes something like: 3.5) Code generation pretends that the fp unit will always be present, so it emits code which uses the fp unit directly in the instruction stream. If a fp unit is not present, the "hardware" in the form of the machines' microcode, emulates the instruction using the machine's integer hardware. No OS trapping is involved and there is no change of control from the user's code.