Line drivers from the FDC chip. Go to page 13 in the schematics, look at the lower right side of the page; see the 7438's? Those might well be suspect. Those require pullups (terminators) on at least one connected drive. Beyond that they're configured as simple OC imverters, so you should be able to find a bad one without replacing it. Just use your logic probe.
Too bad that you don't have a working hard drive to boot from. The floppy lines can be twiddled using a simple debug script.
1st1 the driver for the clock don't seem to load, I'll see if I can find them on c:. but I also can't edit the config or auto exec entries
Then there is this error... is that a wrongly set bios jumper?
There is no driver for the clock that I know of; you have to be running AT&T or Xerox OEM'd MS-DOS 2.x or 3.x for the clock get/set to work. Also, the clock is limited to 3 bits per year; it was meant to cover the years 1984-1992, so putting in any date will work but on bootup the year will be constrained between '84-'92. The time will be correct, though.
Parity Error is a memory error. If you're only seeing it on DMA actions in the customer diags, it's either a real memory error (run the diags for testing memory to be sure), or something else is going on. Are you running AT&T or Xerox OEM 2.x or 3.x MS-DOS? Are your dip switches set for 48 TPI? Were you able to install the 1.43 ROM BIOS which contains compatibility fixes?
I got my AST diagnostic disk to check and read the floppy drives. Drive B is testing good, but drive A has issues.
I wonder if replacing the capacitors on the drive board will help making it run more reliable. I understand that if the motor doesn't spin with the right speed, it will not be able to read data correctly. I don't see any aluminum capacitors on the main board. I will also probably put the boards I remove in my ultrasonic cleaner.
The ATD is not an original memory card from Olivett. Maybe not necessary. What kind of memory chips it has - 4164 or 41256?
Can you check which memory chips are on the long Olivetti memory card? (should be 4164 or 41256), then we know how much memory your machine finally has.
Have also a look on the M24 mainboard. It has memory as well.
All my M24 have 640 kB onboard, that is 18x 4164 and 18x 41256. Its not 16 times, but 18 times, because M24 has memory parity generator and check. Parity error can be hint to defect memory chip.
Older M24 have only 256 kB onboard, that is just 18x 4164. But as far as I remember, it should be expandable onboard, by adding 18x 41256 plus resetting the memory dip switches.
You can also try, if your M24 starts without extra memory in ISA, then it should come up with 128 kB. And then you can do memory test, with only onboard and with the Olivetti memory card. I sugest you to use the M24 customer test utility (see 6300 shrine and the the M24 website previously linked) and Checkit 3.0 (but this does not fit on one 360 kB disk, maybe better try Checkit 2.0), they both have good and reliable memory test tool inside. Olivetti customer test also should run on machine with only 128 kB total memory. So you can see if the error comes from base 128 kB, or from additional memory on memory card.
For having realtime clock, you need to download the clockfix.zip from memtioned websites and follow the instructions to add it to config.sys. If you don't take care about current time on your machine, just forget, the machine also runs perfectly without current time/date.