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The information on this
page
has been provided with kind
permission
of On-Time.
Please
check the pages
at www.on.time.com for updated information.
Benefits of Running without Windows
The most important advantages of not using Windows are:
- Low resource requirements. RTTarget-32's boot code needs only
about 6k of memory. Programs not using the run-time system can run
in as little as 16k total memory. If the run-time system is used,
about 64k is required for the heap and run-time system code.
- Low interrupt latencies. Using RTTarget-32, the interrupt
latency can be as low as about 5 microseconds on a 16Mhz-386SX or
EX. Under Windows, the same CPU can yield several milliseconds
interrupt latency.
- Interrupt handlers in application code. RTTarget-32 allows the
application to install interrupt handlers. This greatly simplifies
the interaction with interrupt-generating hardware and is much
faster than Windows device drivers.
- Hardware access. RTTarget-32 allows the application to directly
access hardware through I/O ports. No overhead is incurred by
emulation or complicated device drivers. Windows does not permit
applications to access ports directly.
- Physical memory access. RTTarget-32 initializes the CPU such
that physical addresses are equal to virtual addresses used by the
application, even if paging is used. This facilitates direct
hardware access through memory mapped devices and the use of DMA.
Windows does not allow access to physical addresses.
- Access to privileged instructions. RTTarget-32 can run
applications at privilege level 3 or 0. Windows supports only
privilege level 3 for applications.
- Speed. Windows needs a substantial amount of CPU time for system
management. With RTTarget-32, this time is freed and made available
to your application. Thus, most applications will run faster under
RTTarget-32 than under Windows. In addition, RTTarget-32's
deterministic behavior makes it suitable for real-time systems.
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