时间：2021-06-14 00:59:50 来源：网络整理编辑：VISATON
A potential drawback to using a protected RTOS in embedded applications is that tasks in the address spaces of protected processes incur more overhead than their unprotected brethren. The reason is that unprotected tasks (tasks running in the kernel's address space) have unlimited access to the entire system and avoid both address-space-switching overhead and translation lookaside buffer (TLB) miss uncertainty. Moreover, unprotected tasks can make direct subroutine calls to kernel routines that avoid the usual parameter checking. By contrast, tasks in protected address spaces must use a special trap or system call instruction to access the kernel, which is frequently slower than a direct call.
Even so, there is nothing to preclude the use of protected RTOSes in high-performance applications, particularly if the RTOS supports both protected and unprotected tasks. With such an RTOS designers can architect the bulk of their system using protected address spaces, while reserving unprotected tasks for the most speed-critical functions. To maximize design flexibility, the RTOS should provide a common API that makes it easy to switch between protected and unprotected mode. For example, during the development phase designers may want to use protected address spaces exclusively in order to simplify debug and testing. Later, designers may want to convert some of the tasks in protected address spaces into unprotected tasks in order to maximize performance in the production system.
One way that a protected RTOS with a non-reentrant kernel can enhance real-time response is to add preemption points to system calls that have long or unbounded response times. These points give the kernel an opportunity to temporarily suspend execution of a particular system call when other, higher-priority events or tasks are pending.
To ensure fast interrupt response, the RTOS should never mask or block interrupts. This allows the highest-priority interrupt to be serviced as quickly as the processor hardware permits. Most RTOSes mask interrupts in order to access critical data structures. This imposes an interrupt latency overhead that the user can't predict or control. To further enhance interrupt response, the RTOS should avoid multicycle instructions such as divides and string operations, which can prevent interrupts from being recognized for the duration of that instruction.
An RTOS' security and protection features provide significant benefits. These security and protection features incur some overhead, but a properly designed RTOS, together with proper design practices, can readily negate this overhead.
Colorado MicroDisplay Inc. (CMD) has received $5 million in funding from Intel Corp. and investment firm 3i U.S. to help it finance ongoing manufacturing, marketing, and product development.
The latest infusion brings to $29 million the total investment capital raised by the Boulder, Colo., company, including equity positions taken by Argo Global Capital, Aweida Ventures Management, Robert Epstein (a co-founder of Sybase), Hambrecht & Quist, In Focus Corp., Sequel Venture Partners, Texas Instruments, and Vulcan Ventures.
CMD did not break out the latest investments, but said the funds from 3i and Intel will allow it to move from R&D to a revenue-generating manufacturing phase that will include production and marketing of a new digital chipset for high-resolution miniature displays.
Current working group representation includes Altera and Synchronicity.
Miller said Rapid has also been working with industry alliances to support their respective projects, and has launched a series of breakfast meetings to bring in industry speakers to discuss IP-related issues. Rapid also is looking to recruit members to chart activities and projects, work on critical IP issues, and represent the IP community, he added.
Intersil Corp. and Fairchild Semiconductor International have agreed to co-develop power-IC technology for next-generation notebook PCs and portable computers.
The strategic initiative will afford both companies' customers a second source for power management circuits for low-voltage, portable computing applications.
This technology partnership makes the most of Intersil's and Fairchild's design and development expertise in power management,” said George Gidzinski, vice president and general manager of Intersil's Analog & Mixed-Signal ICs division The combination of our design and manufacturing resources and expertise through this joint venture will give customers greater access to power ICs for the fast-growing portable-PC market.”
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