Hi Russell, Would something like the following be a reasonable way of detecting a NatSemi PC16552 UART?: if type == 16650A then set LCR.DLAB to 1 if EFR bits 7-3 are 0 then set EFR to 0xff if EFR == 0x07 then set type to 16552 set EFR to 0 fi else restore EFR to previous value fi fi This needs to be inserted before the test for the StarTech ST16650. I've implemented by the attached patch against a 2.4.18 kernel. David