<div id="RTEContent"><pre><tt><tt>>I sort of threw into "I/O" just about everything else other than the<br>>aspects I mentioned: disk access, various actual I/O ports, memory<br>>access. But I meant primarily disk (mass storage subsystem) <br>>performance -- given that gamers _are_ smart enough to ensure adequate amounts of<br>>fast RAM on a fast memory bus.<br><br>The computer industry has been going the way of the <br>automotive industry - do things "good enough", but "cheap".<br>Hardly anyone uses SCSI anymore, many people think SATA is<br>just as fast, because of certain specs the vendors flaunt<br>to encourage such mis-perception. However, what they fail<br>to mention is that SCSI devices have a SCSI controller, and<br>that a SCSI controller is a separate slave microprocessor<br>that handles the bulk of data I/O. When the CPU/operating<br>system wants data from a SCSI device, the SCSI controller<br>is given some basic instructions: 1. where to find the data I
want. <br>2. a location to put that data.<br>The SCSI controller goes about doing its work and transfers<br>the data directly to memory, using a DMA channel to do so.<br>When the data transfer is complete, the SCSI controller<br>signals the CPU that "hey, I'm done, the data you wanted<br>is now where you wanted it." What does this mean to system<br>performance? It means the CPU is free for other activity<br>during a large portion of the data transfer. Under IDE,<br>the CPU is occupied for the entire period of data transfer.<br>While this is a slightly simplified description, it does<br>describe the architecture and salient differences.<br>For most people's computer usage, this performance gain<br>is not enough to justify spending more for SCSI, so people<br>settle for "good enough."<br><br>By the way, SCSI is still expensive. So, how much are you<br>willing to pay for a "smoking" system? Depends on your<br>requirements and the economic costs vs. benefits.<br><br>-
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