| The new world of Windows®CE |
(November.1999) |
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Windows®CE and WindowsNT®/Windows®95/Windows®98 Differences
WindowsNT®/Windows®95/Windows®98 were each developed essentially as a hardware independent PC and CPU OS.
Windows®CE, on the other hand, is an OS that depends heavily on hardware support.
The size of a WindowsNT® kernel is approximately 20MB, whereas a Windows®CE kernel is from 256KB to 2MB. Generally, the BIOS environment of a real-time OS must be configured according to hardware specifications and Windows®CE is no exception.
One reason behind the popularity of Windows®CE is its ability to operate in hardware systems with no hard disk, thereby avoiding problems such as hard disk crashes.
WBT for Windows®CE
WBT(Windows Based Terminal)refers to a new client-server environment where a WindowsNT® server with a hard disk is accessed by Windows®CE client terminals over a LAN.
WBT allows each Windows®CE terminal to open a window for itself on the NT server.
If the task is just displaying a client or zone, or accessing an OS-supported I/O device, all processing is straightforward. However, for key operations or communication involving PLC protocols, the OS environment would need to be customized and require extensive testing and expertise to set up. Also, during operation, since each Windows task on the NT server is linked with one client, the number of clients that can simultaneously access the serverdepends completely on the hardware performance of the NT server.
Real Time Capabilities
The following tests were conducted by Microsoft, run-ning Windows®CE V2.11 with a 100MHz Pentium II. The results were as follows.
ISR(Interrupt Service Routine)
Time: average 10 sec, worst-case 25 sec
IST(Interrupt Service Thread)
Time: average 25 sec, worst-case 50 sec
These times, however, include the overhead required to handle disk and mouse related operations.
How fast would these times be without the HDD, mouse and FDD operation overhead?
We could expect a lot less time to be lost switching between tasks.
In fact, a product named DCX, produced by VenturCom Incorporated, uses task switching to provide a Windows®CE environment that operates at 10 sec or faster. A product such as DCX makes it easier to build task structures and drivers in Microsoft ETK environments. |
Masashi Murakami, Director, New Business Planning Division |
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