Retidy, removing align=left from headings and empty paragraphs
This commit is contained in:
James Gregory
parent
7b08bb15c6
commit
a96a114403
362 changed files with 8472 additions and 5040 deletions
37
03-10.html
37
03-10.html
|
|
@ -1,5 +1,4 @@
|
|||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
|
||||
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||||
<!DOCTYPE html>
|
||||
|
||||
<html xmlns="http://www.w3.org/1999/xhtml">
|
||||
<head>
|
||||
|
|
@ -19,17 +18,21 @@
|
|||
<center>
|
||||
<table border="1">
|
||||
<tr>
|
||||
<td><a href="03-09.html">Previous</a></td>
|
||||
<td>
|
||||
<a href="03-09.html">Previous</a>
|
||||
</td>
|
||||
|
||||
<td><a href="index.html">Table of Contents</a></td>
|
||||
<td>
|
||||
<a href="index.html">Table of Contents</a>
|
||||
</td>
|
||||
|
||||
<td><a href="04-01.html">Next</a></td>
|
||||
<td>
|
||||
<a href="04-01.html">Next</a>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
|
||||
<p><br /></p>
|
||||
|
||||
<p>when declaring the timer routines <b>extern</b>, so that name-mangling doesn’t occur, and the linker can find the routines’ C-style names.)</p>
|
||||
|
||||
<p>That’s all it takes; after doing this, you’ll be able to use the Zen timer from C, as, for example, in:</p>
|
||||
|
|
@ -50,7 +53,7 @@ ZTimerReport();
|
|||
|
||||
<p>The full listings for the C-callable Zen timers are presented in Chapter K on the companion CD-ROM.</p>
|
||||
|
||||
<h4 align="left" id="Heading16">Watch Out for Optimizing Assemblers!</h4>
|
||||
<h4 id="Heading16">Watch Out for Optimizing Assemblers!</h4>
|
||||
|
||||
<p>One important safety tip when modifying the Zen timer for use with large code model C code: Watch out for optimizing assemblers! TASM actually replaces</p>
|
||||
<pre>
|
||||
|
|
@ -76,28 +79,32 @@ call near ptr ReferenceZTimerOn
|
|||
|
||||
<p>I’ve tested the changes shown in Figures 3.2 and 3.3 with TASM and Borland C<small>++</small> 4.0, and also with the latest MASM and Microsoft C/C<small>++</small> compiler.</p>
|
||||
|
||||
<h4 align="left" id="Heading17">Further Reading</h4>
|
||||
<h4 id="Heading17">Further Reading</h4>
|
||||
|
||||
<p>For those of you who wish to pursue the mechanics of code measurement further, one good article about measuring code performance with the 8253 timer is “Programming Insight: High-Performance Software Analysis on the IBM PC,” by Byron Sheppard, which appeared in the January, 1987 issue of <i>Byte</i>. For complete if somewhat cryptic information on the 8253 timer itself, I refer you to Intel’s <i>Microsystem Components Handbook</i>, which is also a useful reference for a number of other PC components, including the 8259 Programmable Interrupt Controller and the 8237 DMA Controller. For details about the way the 8253 is used in the PC, as well as a great deal of additional information about the PC’s hardware and BIOS resources, I suggest you consult IBM’s series of technical reference manuals for the PC, XT, AT, Model 30, and microchannel computers, such as the Models 50, 60, and 80.</p>
|
||||
|
||||
<p>For our purposes, however, it’s not critical that you understand exactly how the Zen timer works. All you really need to know is what the Zen timer can do and how to use it, and we’ve accomplished that in this chapter.</p>
|
||||
|
||||
<h4 align="left" id="Heading18">Armed with the Zen Timer, Onward and Upward</h4>
|
||||
<h4 id="Heading18">Armed with the Zen Timer, Onward and Upward</h4>
|
||||
|
||||
<p>The Zen timer is not perfect. For one thing, the finest resolution to which it can measure an interval is at best about 1µs, a period of time in which a 66 MHz Pentium computer can execute as many as 132 instructions (although an 8088-based PC would be hard-pressed to manage two instructions in a microsecond). Another problem is that the timing code itself interferes with the state of the prefetch queue and processor cache at the start of the code being timed, because the timing code is not necessarily fetched and does not necessarily access memory in exactly the same time sequence as the code immediately preceding the code under measurement normally does. This prefetch effect can introduce as much as 3 to 4 µ of inaccuracy. Similarly, the state of the prefetch queue at the end of the code being timed affects how long the code that stops the timer takes to execute. Consequently, the Zen timer tends to be more accurate for longer code sequences, since the relative magnitude of the inaccuracy introduced by the Zen timer becomes less over longer periods.</p>
|
||||
|
||||
<p>Imperfections notwithstanding, the Zen timer is a good tool for exploring C code and x86 family assembly language, and it’s a tool we’ll use frequently for the remainder of this book.</p>
|
||||
|
||||
<p><br /></p>
|
||||
|
||||
<center>
|
||||
<table border="1">
|
||||
<tr>
|
||||
<td><a href="03-09.html">Previous</a></td>
|
||||
<td>
|
||||
<a href="03-09.html">Previous</a>
|
||||
</td>
|
||||
|
||||
<td><a href="index.html">Table of Contents</a></td>
|
||||
<td>
|
||||
<a href="index.html">Table of Contents</a>
|
||||
</td>
|
||||
|
||||
<td><a href="04-01.html">Next</a></td>
|
||||
<td>
|
||||
<a href="04-01.html">Next</a>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
|
|
|
|||
Loading…
Reference in a new issue