Right well I half figured it out , the single bit overrides the drive to be the only recognized drive on that header.
No idea what the factory bit means though.

Looks like the IDE master/slave selector to me. The Factory pins are probably for debugging.

Master/Slave/Cable select are jumpers in "Jumper Block", I think. This single jumper is designed for configuration where there is only one IDE/ATA device on the cable (that is, this CD ROM drive). Some HDDs had it too.

That's a quite inventive set of jumpers. Which brand/model drive is this?

Some IDE CD drives have jumpers to prevent the drive from operating in Ultra DMA modes to improve compatibility with older controllers.

I have a Liteon 32x, a NEC cd burner, and some others with those extra 3 jumps and look nearly identical in back, AFAIK you do not use those for standard PC setups.
Factory is for a final test/calibration of the drive and that Single drive is for a specific use, Apple possibly or upgrade flashing the rom in a multi CD setup to make sure that just one gets flashed) iirc
(been a long time since I even thought about those so am probably remembering wrong from decades ago..)
If you look at many early PC cd burners you will see a space for those same jumpers but they are not there because they were not for "end users" ;p
just rambling...

dionb wrote on 2022-09-21, 07:42:

That's a quite inventive set of jumpers. Which brand/model drive is this?

It's a NEC CDR 273

https://stason.org/TULARC/pc/optical-cd-drive … OM-CDR-273.html

Horun wrote on 2022-09-22, 03:27:

I have a Liteon 32x, a NEC cd burner, and some others with those extra 3 jumps and look nearly identical in back, AFAIK you do […]
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I have a Liteon 32x, a NEC cd burner, and some others with those extra 3 jumps and look nearly identical in back, AFAIK you do not use those for standard PC setups.
Factory is for a final test/calibration of the drive and that Single drive is for a specific use, Apple possibly or upgrade flashing the rom in a multi CD setup to make sure that just one gets flashed) iirc
(been a long time since I even thought about those so am probably remembering wrong from decades ago..)
If you look at many early PC cd burners you will see a space for those same jumpers but they are not there because they were not for "end users" ;p
just rambling...

That's really odd , you'd think they wouldn't leave that kind of stuff exposed for consumers or at least hide it somewhere inside the drive on the pcb.

You can see this on some old HDD´s too, it´s really for configuration, where only this device alone is connected on the cable:

Ydee wrote on 2022-09-24, 16:41:

You can see this on some old HDD´s too, it´s really for configuration, where only this device alone is connected on the cable:

Yeah the single thing makes sense , its more the factory setting that's a bit odd.