The SCSI firmware writes that no termination was found. The SCSI bus must have termination on both ends. So you need:

SCSI controller -> termination enable
First HD-MAE3091LP (middle of the cable) -> termination disable
Second HD-MAE3091LP (end of the cable) -> termination enable

You should also check the Adaptec-Setup (Ctrl-A). Usually this also works without terminator.

Can you find a 24pin connector CN2 on your drive? According to the manual shorting pins 23 and 24 will provide termination power.

Note that termination power is not termination. Termination is most likely done by installing two/three resistor networks or by using a separate terminator at the cable's end. Unless there's another jumper somewhere that clearly says "termination".

derSammler wrote:

The SCSI firmware writes that no termination was found. The SCSI bus must have termination on both ends. So you need: […]
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The SCSI firmware writes that no termination was found. The SCSI bus must have termination on both ends. So you need:

SCSI controller -> termination enable
First HD-MAE3091LP (middle of the cable) -> termination disable
Second HD-MAE3091LP (end of the cable) -> termination enable

Modifying the BIOS the result is wrong

Predator99 wrote:

You should also check the Adaptec-Setup (Ctrl-A). Usually this also works without terminator.

I have nothing clear to do in this menu 😵

Host adapter defaults

lazibayer wrote:

Can you find a 24pin connector CN2 on your drive? According to the manual shorting pins 23 and 24 will provide termination power.

Pins originally connected to both disks

Disk A

Disk B

The result is wrong

Are both drives connected on the same cable or two separate cables? Both drives are set to ID0 so they cannot coexist on the same cable.
Are you using terminator(s)?

Modifying the BIOS the result is wrong

Termination is still off in that screenshot.

I second the question: how exactly is everything connected? Can you make a photo?

lazibayer wrote:

Are both drives connected on the same cable or two separate cables? Both drives are set to ID0 so they cannot coexist on the same cable.
Are you using terminator(s)?

Both drives are connected on the same cable

All the pieces are in their original position, except the Bios (default)

I have no terminator, the HDs are connected as they were originally

derSammler wrote:

Modifying the BIOS the result is wrong

Termination is still off in that screenshot.

I second the question: how exactly is everything connected? Can you make a photo?

Looks like you have the drives connected to channel 1, which has termination disabled in the BIOS. Turn on termination there and see if you have better luck.

Also, remove the TERM PWR jumper from the drive in the middle of the chain and change one of the two drives to a different SCSI ID. (They cannot both be on the same ID. That's like having two IDE drives both jumpered to master, but worse. It shouldn't matter what ID you change to. Use the extra jumper you yoinked from the TERM PWR pins to do so.) You shouldn't need the START CMD or SINGLE/WIDE jumpers set either. They're the same model, they're both LVD/SE on what is, IIRC, an LVD bus, so you shouldn't need those.