CPU Utilization

By Loyd Case  |  Posted 2003-01-16 Print this article Print

Whats probably at issue here is the CPU utilization. Heres the relevant chart of CPU utilization. The USB drive posts a whopping 66.6% CPU utilization -- higher is definitely not better here, folks.
If you think about it, 480 megabits/sec -- the theoretical maximum for USB 2.0 -- is around 60 megabytes per second. Even if you postulate a 20% overhead for encoding, then you still should see around 48MB/sec, assuming no other activity on the USB port. However, the lack of DMA necessarily means the CPU gets heavily involved in data transfers -- which will translate to a lower maximum transfer rate.
Note that this CPU utilization is measured during a situation where the drive is blasting the maximum amount of data across the bus (high-speed sequential reads). In situations where you might be reading and writing from the drive in more random patterns, you probably wont notice such a severe CPU hit.

Loyd Case came to computing by way of physical chemistry. He began modestly on a DEC PDP-11 by learning the intricacies of the TROFF text formatter while working on his master's thesis. After a brief, painful stint as an analytical chemist, he took over a laboratory network at Lockheed in the early 80's and never looked back. His first 'real' computer was an HP 1000 RTE-6/VM system.

In 1988, he figured out that building his own PC was vastly more interesting than buying off-the-shelf systems ad he ditched his aging Compaq portable. The Sony 3.5-inch floppy drive from his first homebrew rig is still running today. Since then, he's done some programming, been a systems engineer for Hewlett-Packard, worked in technical marketing in the workstation biz, and even dabbled in 3-D modeling and Web design during the Web's early years.

Loyd was also bitten by the writing bug at a very early age, and even has dim memories of reading his creative efforts to his third grade class. Later, he wrote for various user group magazines, culminating in a near-career ending incident at his employer when a humor-impaired senior manager took exception at one of his more flippant efforts. In 1994, Loyd took on the task of writing the first roundup of PC graphics cards for Computer Gaming World -- the first ever written specifically for computer gamers. A year later, Mike Weksler, then tech editor at Computer Gaming World, twisted his arm and forced him to start writing CGW's tech column. The gaming world -- and Loyd -- has never quite recovered despite repeated efforts to find a normal job. Now he's busy with the whole fatherhood thing, working hard to turn his two daughters into avid gamers. When he doesn't have his head buried inside a PC, he dabbles in downhill skiing, military history and home theater.

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