| Unknown World of Windows®CE |
(April, 1999) |
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Differences between Windows®CE and WindowsNT®/Windows®95/Windows®98
The concept behind Microsoft's WindowsNT®/Windows®95/Windows®98 was to create OSs that would be independent of hardware (i.e. the personal computer and the CPU). On the contrary, Windows®CE is, for the most part, completely dependent on the surrounding hardware.
While the kernel size of a WindowsNT® is about 20MB, a Windows®CE kernel is anywhere from 256KB to about 2MB. The idea that a real time OSs' BIOS environment needs to be set up according to the surrounding hardware's specifications has been around for some time, and this is a primary idea behind Windows®CE.
The industry's expectation is that Windows®CE, with its 256KB kernel size, Windows-like operating environment and high degree of hardware dependence, can lead to the realization of a "hard disk-less" environment, thereby solving a number of problems caused by hard disk crashes.
Windows®CE's WBT and ETK
With a WBT (Windows-Based Terminal), WindowsNT® is used as the server OS and a client, with hardware that has Windows®CE installed, is connected to the server via a LAN. This allows the WindowsNT®'s Windows tasks and the client's Windows®CE to be connected via a data communication network. As a result, one of the NT server "windows" can be opened to the Windows®CE hardware. To simply display data on the client or use a hardware manufacturer's existing I/O, WBT is easy to use, however, if you wish to utilize communication features such as key operations and PLC protocols, you will need to build and test a special OS environment, which requires special techniques.
In addition, since the client is linked with one Windows task on the NT server, the number of clients whose Windows tasks can be opened depends on the NT server's hardware performance. Therefore, it is natural that as the number of open Windows tasks increases, the more server performance will degrade. Prior to using a WBT, please check that minimum system performance levels will not be compromised, and be aware that performance-related problems may occur.
The ETK (Extended Tool Kit) is used to embed Windows®CE into hardware.he Japanese document environment has been available since last March and is still being improved slowly. Wheneverhardware specifications are changed, however, system rebuilding is required. Digital is currently holding discussions with Microsoft Japan and other related companies to provide an easy-to-use environment to our users.
Real Time Performance
Microsoft has performed real time performance tests using a fully equipped personal computer with Windows®CE Version 2.11 and a Pentium® II 100MHz processor.
The results were as follows:
ISR time: Average of 10msec, worst case: 25msec
IST time: Average of 25msec, worst case: 50msec
These values, however, include the checking of a fully equipped PC's BIOS for HDD, mouse, etc. operations. Time losses caused by this OS checking are also included in these values. What about performance if we do not check these items? We can expect, in that case, that task change time would be greatly reduced.
Currently, Microsoft is reviewing this point. VenturCom Inc.'s DCX can provide a Windows®CE environment with a task change time of 10msec or less.
DCX facilitates the task and driver creation architecture in Microsoft's ETK environment. Also, DCX functions as an OPC server, and OMAC is using it to test the SoftPLC currently being developed by OMAC related PLC manufactures. |
Masashi Murakami, Sub-chief of the Product Planning Department |
For the detailed information about Windows CE, please see the following Microsoft web page.
http://www.microsoft.com/windowsce/default.asp |
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