Passive Release

Common Options : Enabled, Disabled

Quick Review

This BIOS feature controls the passive release feature of the CPU to PCI Write Buffer. Therefore, if the write buffer is disabled, this BIOS feature will not have any effect. However, the reverse is not true. The CPU to PCI Write Buffer feature will still work even if Passive Release is disabled.

When Passive Release is enabled, the write buffer will independently write the data to the PCI bus at the first available opportunity. It can do so even when the processor is busy doing something else.

When Passive Release is disabled, the write buffer will wait till the processor reasserts (retries) the write request. Only then will it write to the PCI bus. This still improves performance because the processor does not need to resend the data. However, the write buffer still loses some of its effectiveness because it has to wait for the CPU to retry the transaction.

For best performance, it is highly recommended that you enable Passive Release. This will dramatically reduce the effect of slow ISA devices hogging the PCI bus. However, some ISA cards may not work well with Passive Release. In such cases, disable Passive Release or better yet, throw the card away and get a PCI version instead!

If you don't use any ISA device, this feature should still be enabled because it allows the write buffer to offload its data to the PCI bus without waiting for the processor to retry the transaction. This improves the performance of the processor and PCI bus.

Please note again that this BIOS feature will have no effect if you disable the CPU to PCI Write Buffer.

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