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CONFIG_SCSI_NCR53C8XX_SYNC: synchronous transfers frequency in MHz

General informations

The Linux kernel configuration item CONFIG_SCSI_NCR53C8XX_SYNC has multiple definitions:

synchronous transfers frequency in MHz found in drivers/scsi/Kconfig

The configuration item CONFIG_SCSI_NCR53C8XX_SYNC:

Help text

The SCSI Parallel Interface-2 Standard defines 5 classes of transfer rates: FAST-5, FAST-10, FAST-20, FAST-40 and FAST-80. The numbers are respectively the maximum data transfer rates in mega-transfers per second for each class. For example, a FAST-20 Wide 16 device is able to transfer data at 20 million 16 bit packets per second for a total rate of 40 MB/s.

You may specify 0 if you want to only use asynchronous data transfers. This is the safest and slowest option. Otherwise, specify a value between 5 and 80, depending on the capability of your SCSI controller. The higher the number, the faster the data transfer. Note that 80 should normally be ok since the driver decreases the value automatically according to the controller's capabilities.

Your answer to this question is ignored for controllers with NVRAM, since the driver will get this information from the user set-up. It also can be overridden using a boot setup option, as follows (example): 'ncr53c8xx=sync:12' will allow the driver to negotiate for FAST-20 synchronous data transfer (20 mega-transfers per second).

The normal answer therefore is not to go with the default but to select the maximum value 80 allowing the driver to use the maximum value supported by each controller. If this causes problems with your SCSI devices, you should come back and decrease the value.

There is no safe option other than using good cabling, right terminations and SCSI conformant devices.

synchronous transfers frequency in MHz found in drivers/scsi/Kconfig

The configuration item CONFIG_SCSI_NCR53C8XX_SYNC:

Help text

The SCSI Parallel Interface-2 Standard defines 5 classes of transfer rates: FAST-5, FAST-10, FAST-20, FAST-40 and FAST-80. The numbers are respectively the maximum data transfer rates in mega-transfers per second for each class. For example, a FAST-20 Wide 16 device is able to transfer data at 20 million 16 bit packets per second for a total rate of 40 MB/s.

You may specify 0 if you want to only use asynchronous data transfers. This is the safest and slowest option. Otherwise, specify a value between 5 and 80, depending on the capability of your SCSI controller. The higher the number, the faster the data transfer. Note that 80 should normally be ok since the driver decreases the value automatically according to the controller's capabilities.

Your answer to this question is ignored for controllers with NVRAM, since the driver will get this information from the user set-up. It also can be overridden using a boot setup option, as follows (example): 'ncr53c8xx=sync:12' will allow the driver to negotiate for FAST-20 synchronous data transfer (20 mega-transfers per second).

The normal answer therefore is not to go with the default but to select the maximum value 80 allowing the driver to use the maximum value supported by each controller. If this causes problems with your SCSI devices, you should come back and decrease the value.

There is no safe option other than using good cabling, right terminations and SCSI conformant devices.

Hardware

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