i was searching for a product called 1SC by Firmtek - and there is none..
i suppose you mean the Firmtek Seritek 1SC1?
https://eshop.macsales.com/item/Firmtek/SATA1SC1/im pretty sure if you contact firmtek they will tell u that the products are not meant to be used as you are using them, using multiple adapters like that is not always compatible.. the firmware programming in the devices do a fair bit of logic on boot, and im pretty sure u are trying an incompatible combination of devices here.
the 1SC1 is not meant to be used in tandem with another Firmtek sata adapter to pci.. you are coming at this all wrong..
ie: if u were to use the 1SC1 product properly this would be to connect a SATA drive to an IDE bus.
lets just look carefully at the description?
The SeriTek/1SC1 is a Parallel ATA (PATA) to Serial ATA (SATA) converter.
It allows you to utilize new SATA interface technologies with your current PATA drives.
For IDE or ATA 40 Pin Hard Drives to SATA (Serial ATA).
Use drives from your G4 inside your G5 (not for the Mac Pro)!
this product was brought to market to be used to connect a PATA drive inside a G5 which has a BUILT IN SATA controller im pretty sure its NOT meant to be used with the 1v4... the problem being that the firmwares logic does certain investigation of your setup.. and your sending the logic into an endless loop or fucking it up in some way ie: the openfirmware paths are not resolving properly..
just please buy a new SATA Drive and save your hair.
now that im thinking about this i remember trying such a combination in a good number of different macs that i have and i always had major problems trying to use two adapters in combination like that..
some of them "worked" but it was buggy as hell and some just refused to work.. (i was testing with a Sonnet Tempo sata card which is a clone of the Firmtek 1S2)
botom line.. for all reading this.. dont mix + match any type of storage tech Adapter in combination with another adapter. this is a mac.. its not lego.. u cant mix + match components every which way just because the connectors fit doesnt mean its going to work.. use the products as simply as possible.. as they were intended to be used so that they work properly...