http://www.alphalinux.org/wiki/index.php?title=Byte/Word_Extension&feed=atom&action=historyByte/Word Extension - Revision history2024-03-29T05:42:28ZRevision history for this page on the wikiMediaWiki 1.31.7http://www.alphalinux.org/wiki/index.php?title=Byte/Word_Extension&diff=81&oldid=prevGareth: Imported from http://web.archive.org/web/20110529084508/http://www.alphalinux.org/wiki/index.php?title=Byte/Word_Extension&action=edit2019-08-29T18:11:42Z<p>Imported from http://web.archive.org/web/20110529084508/http://www.alphalinux.org/wiki/index.php?title=Byte/Word_Extension&action=edit</p>
<p><b>New page</b></p><div>The Byte/Word eXtensions were first introduced in the [[Processors#EV56|EV56]] and has been available in all subsequent models. The instructions were provided to reduce the number of instructions for operations such as loading and storing bytes or words to and from memory and sign-extending of byte and word values.<br />
According to the Alpha Architecture Handbook <ref>{{cite web|url=http://h18002.www1.hp.com/cpq-alphaserver/technology/literature/alphaahb.pdf|title=Alpha Architecture Handbook|year=1998|month=October|format=PDF|publisher=Compaq Computer Corporation|pages=103}}</ref> it is recommended to use these instructions on platforms where they are present instead of the sequences of extract, mask and insert instructions that would otherwise be needed.<br />
<br />
== Added Instructions ==<br />
<br />
{| class="wikitable" style="font-size:97%;"<br />
! Mnemonic<br />
! Description<br />
|-<br />
! LDBU<br />
| Load byte unaligned<br />
|-<br />
! LDWU<br />
| Load word unaligned<br />
|-<br />
! SEXTB<br />
| Sign-extend byte<br />
|-<br />
! SEXTW<br />
| Sign-extend word<br />
|-<br />
! STB<br />
| Store byte<br />
|-<br />
! STW<br />
| Store word<br />
|}<br />
<br />
== Determining Presence ==<br />
<br />
To determine the presence of BWX, use the [[amask]] instruction.<br />
<br />
== References ==<br />
<references/><br />
<br />
[[Category:Programming]]</div>Gareth