Cyberstorm PPC SCSI transfer rates ?

[patrik]

The only thing you should need to do is to set the transfer-mode to synchronous and 20MHz for the ID-number of your harddrive in scsi-part of the bootmenu-settings (entered by pressing esc at boot). For the other settings of the harddrive id, just set them to auto. If your cabling/termination/harddrive doesn't manage those speeds, the controller will sense that and run it slower.


/Patrik

[patrik]

The two flags which are contained in the RDB - the Synchron and Reselection flag, are only used if "Async/Synchron" (Auto) mode respective "Auto Reselection" is used.

If you, in the bootmenu set "Async" or "Synchron" respective "Reselection" or "No Reselection" the values for these flags set in the RDB will be ignored.

Also, say if you set 20MHz synchronous and the controller judges that your cabling/termination/harddrive combo isn't up to the task, it will revert to a lower speed, which can make it feel like the settings in the bootmenu doesn't make much difference.


/Patrik

[patrik]

@motorollin:

The CSPPC/CSMK3 doesn't have an onboard terminator, so his setup is as it should be.


/Patrik

[patrik]

@Mugo:

The speed-setting for the synchronous setting in the bootmenu is in MHz. As it is a wide scsi-interface (16-bit), 20MHz * (16bits/8) = 40MB/s.

The flags in the RDB are ignored if you set it to "Synch" or "Asynch" for the synchronous flag and "No Reselection" or "Reselection" for the reselection flag. They are only read from RDB if you set them to "Asynch/Sync" respective "Auto Reselection".

As the controller will sense if your cabling/termination/harddrive can manage the speeds you have set 100% reliable, it might be something isnt up to the task. I think it reverts back to asynchronous if that is the case, but I am not sure I remember right. Anyhow, try setting it to asynchronous and just a bit over 10MHz - say 11 or 12MHz and see if that increases the speed over previous attempts.

Measure the raw transfer-rate with ScsiSpeed from the DiskSpeed package, then filesystem won't interfer with the results.


/Patrik