48 lines
2.9 KiB
HTML
48 lines
2.9 KiB
HTML
<html><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<html>
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<head>
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<title>80386 Programmer's Reference Manual -- Section 10.1</title>
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</head>
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<body>
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<b>up:</b> <a href="C10.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C10.HTM">Chapter 10 -- Initialization</a><br>
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<b>prev:</b> <a href="C10.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C10.HTM">Chapter 10 -- Initialization</a><br>
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<b>next:</b> <a href="S10_02.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/S10_02.HTM">10.2 Software Initialization for Real-Address Mode</a>
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<p>
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<hr>
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<p>
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<h1>10.1 Processor State After Reset</h1>
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The contents of EAX depend upon the results of the power-up self test. The self-test may be requested externally by assertion of BUSY# at the end of RESET. The EAX register holds zero if the 80386 passed the test. A nonzero value in EAX after self-test indicates that the particular 80386 unit is faulty. If the self-test is not requested, the contents of EAX after RESET is undefined.
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<p>DX holds a component identifier and revision number after RESET as <a href="#fig10-1">Figure 10-1</a> illustrates. DH contains 3, which indicates an 80386 component. DL contains a unique identifier of the revision level.
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<p>Control register zero (CR0) contains the values shown in <a href="#fig10-2">Figure 10-2</a> . The ET bit of CR0 is set if an 80387 is present in the configuration (according to the state of the ERROR# pin after RESET). If ET is reset, the configuration either contains an 80287 or does not contain a coprocessor. A software test is required to distinguish between these latter two possibilities.
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<p>The remaining registers and flags are set as follows:
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<pre>
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EFLAGS =00000002H
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IP =0000FFF0H
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CS selector =000H
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DS selector =0000H
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ES selector =0000H
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SS selector =0000H
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FS selector =0000H
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GS selector =0000H
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IDTR:
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base =0
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limit =03FFH
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</pre>
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All registers not mentioned above are undefined.
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<p>These settings imply that the processor begins in real-address mode with interrupts disabled.
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<p><a name="fig10-1"><img align="center" src="FIG10-1.GIF" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/FIG10-1.GIF" border="0">
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<hr>
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<a name="fig10-2"><img align="center" src="FIG10-2.GIF" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/FIG10-2.GIF" border="0">
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<p>
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<hr>
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<p><b>up:</b> <a href="C10.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C10.HTM">Chapter 10 -- Initialization</a><br>
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<b>prev:</b> <a href="C10.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C10.HTM">Chapter 10 -- Initialization</a><br>
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<b>next:</b> <a href="S10_02.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/S10_02.HTM">10.2 Software Initialization for Real-Address Mode</a>
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</body>
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