There are a number of CF cards that don't follow the ATA specs regarding RESET line behavior, more specifically, they totally ignore the RESET line....
There are two issues that may occur when using those CF cards in a net5501:
1) The "set flash=primary|secondary" setting is done by setting the CSEL (cable select) line to master or slave and then issuing a reset. The CF card are then supposed to reset and recognize the new CSEL setting.
CF cards that don't do that will just use the hardware default. In early net5501's that was slave, we changed that to master so at least non standard CF cards could be used in the most common way.
2) Some boards have a problem with a short glitch on the DASP line. That shouldn't normally matter as we do a RESET afterwards, but again some CF cards ignore the RESET line.... During initial power up, if the CF card is master it will then wait 32 seconds for the slave response and if that is not present then the BIOS will time out and not recognize the CF card. The CF card then shows up and works when doing a soft reset ("reboot" command in comBIOS).
For 2) we have changed the timeout in comBIOS vers 1.33c so the CF card can be used, although there will be a delay during cold resets.
We will also implement a hardware workaround for the glitch in future production series but the non standard CF cards will of course still only be master.
If a CF card cannot be set to slave then it will not follow the ATA standard and is not recommended to be used in Soekris boards.
We recommend using Sandisk CF cards as they seem to follow the specs and therefore work as expected.