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文章阅读:[转载] Wonderful World of Linux 2.4 (part IV)
[版面: Linux 操作系统] [作者:ayanami] , 2000年11月26日17:54:52
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发信人: ayanami (发情的蚊子~甲亢中), 信区: Linux
标  题: [转载] Wonderful World of Linux 2.4 (part IV)
发信站: The unknown SPACE (Sun Nov 26 17:54:52 2000), 转信

【 以下文字转载自 ITnews 讨论区 】
【 原文由 ayanami 所发表 】
System Buses - ISA, PCI, USB, MCA, etc.

Processors are just one small part of the nifty world that
exists inside your computer. Equally important is the
computer's bus architecture, the component(s) of the system
that is often responsible for internal and external devices.
Some bus architectures, such as the original ISA, are more
irresponsible towards their hardware than anything else--
they don't provide any resource management
functionality,just a place to put in cards. Others, such as
PCI, support much more advanced levels of configuration and
allow for devices to be relocated in memory and other
things. As of Linux 2.2, all major buses used on Intel
hardware are supported including (E)ISA, VLB, PCI, and the
newest addition(an older bus only popular on IBM hardware),
MCA. Linux 2.4 expands on this support by including direct
support for ISA Plug-and-Play devices (a scheme to make ISA
devices almost as intelligent as PCI ones) and I2O devices.
But perhaps most importantly, Linux 2.4 is the first version
of the Linux kernel to provide a robust system for resource
management. During the development of Linux 2.4, it became
apparent that such a system would be a requirement if Linux
were to ever completely support USB, PC cards, or any number
of other modern hardware advances and take its rightful
place as a "modern"operating system.

ISAPnP has long been a major issue for Linux users. Although
support for ISA hardware has dwindled in favor of more
robust PCI hardware, many budget devices are still sold that
use ISAPnP. Previously, Linux users could get ISAPnP
hardware working by using often frustrating pnp utilities
that could require hours of tweaking to get quite right.
Some distributions attempted to automate this process, but
none met with any great level of success. As the Linux 2.4
development progressed, it became apparent that it would be
easy and beneficial to integrate ISAPnP support into the
resource manager.(Although as of this writing, not all
drivers have been recoded to take advantage of its
features.) Sadly however, Linux 2.4's support for ISAPnP at
the kernel level comes at a time when actual PnP hardware is
relatively uncommon Had this functionality been available
earlier, more users could have benefited.

In contrast, Linux is right on the bleeding edge with its
support for I2O devices, a new more "intelligent" superset
of PCI. Relatively revolutionary in its day, PCI was a great
improvement as it provided for centralized management of
devices' memory ranges, registers, etc. I2O devices go the
next level by providing an API at the device level that will
allow OS independent drivers to be provided for devices. The
underlying OS then need only understand the "generic" I2O
APIs to use the device instead of the hardware-specific
ones. As this technology is relatively new, not many devices
have been manufactured to take advantage of this yet, but
Linux will be ready if and when they show up in the
marketplace.

Much of the major work with devices recently has not been
with the internal busses, but rather with external ones such
as the PC Card bus, and the various serial busses. The most
common variety of external device is the PC Card (formerly
known as a PCMCIA card). Linux 2.4 includes,at long last,
support for these devices in a stock kernel. (Previously, it
was possible to download a driver from an external source;
nearly every distribution actually chose to do this.) Of
course, an external daemon and other components will still
be required to make the most out of these devices.

Perhaps the most exciting news on this front is the
Universal Serial Bus (USB), an external bus that is coming
into prominence for devices such as keyboards, mice, sound
systems, scanners, and printers. USB is a popular option on
many new pieces of hardware,   including non-Intel hardware.
Linux's support for these devices is still in early stages
but a large percentage of common USB   hardware (including
keyboards, mice, speakers,etc.) is already supported in the
kernel.

And even more recently, Firewire (IEE1394) support has been
added into the Linux kernel. Firewire is a popular option
for many high-bandwidth devices. Not many drivers (or
devices) exist for this hardware architecture yet, but this
support is likely to improve over time, as the architecture
matures.


--
Linux is only free when your time has no value
                                - JWZ

※ 来源:.The unknown SPACE bbs.mit.edu.[FROM: 167.95.252.64.s]
--
※ 转载:.The unknown SPACE bbs.mit.edu.[FROM: 64.252.95.167]

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