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| Newsletter |
| Slow Operation of PC Cards in Windows NT4 |
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The Elcard
PCIBridge driver has built in detection logic that detects a poorly written IRQ handler for a PC-Card that would
normally crash the PC. When a "Dirty IRQ Handler" is detected, the IRQ is disabled and handled by polling on a timer
tick, so transfer performance may be poor, however the PC does not crash as it would with out the Elcard PCIBridge
driver. The Microsoft Windows NT4 ATA driver (ATDISK.SYS) is one such "Dirty IRQ Handler" driver, and for this reason the Elcard PCIBridge driver is set up in Windows NT4 to enable polled mode for best transfer performance without crashing the PC. Sometimes, the PC Card hardware associated with a correctly written "Clean IRQ Handler ;-)" driver may defeat the "Dirty IRQ Handler" detection logic and it may go to polled mode. In this case, try this registry setting. If your PC Card's performance is even worse, then revert back to the old setting with this registry setting; your card has a "Dirty IRQ Handler" and the only solution is to contact your PC Card vendor for a driver update for their PC Card. NOTE: The above settings can be made in Windows 2000 and Windows NT4 operating systems. Do not use them in Windows9x or WindowsMe. Further information for developers:It is recommended that device driver writers should write their IRQ handlers for their PC Cards using Microsoft's current recommended guidelines in the Windows NT/2000 DDK for PCI devices that are capable of sharing an IRQ. See the Microsoft Windows NT/2000 DDK for more information. |