I have upgraded CPU's in two of my computers and these are now identified with new computer ID's, obviously. The computer with ID 990896 is a HP ProDesk 400 G4 and the computer with ID 1040565 is a Dell OptiPlex 7060 micro. Replaced i5-8500T with i7-8700T in both. Tried to merge and no problem with the HP, but was refused with the Dell. Got this explanation:

"Host 1040565 has an incompatible CPU: (GenuineIntel Intel(R) Core(TM) i7-8700T CPU @ 2.40GHz [Family 6 Model 158 Stepping 10], GenuineIntel Intel(R) Core(TM) i5-8500T CPU @ 2.10GHz [Family 6 Model 158 Stepping 10])"

Still, it is the very same computer though and the CPU's of concern are indeed compatible ... (Compare the Family, Model and Stepping codes.) An incompatible CPU would be any one from the 6th and 7th generation or any from 8th and 9th generation with a TDP higher than 35W.
(Gen. 6 and 7 CPU's are using the 1151/H4r1 socket, while gen. 8 and 9 are using the 1151-1/H4r2. Both socket versions have the same mechanical spec's, but different electrical spec's. Mixing will fry the CPU and/or the motherboard. If unlucky, there might be problems with the memory modules too.)

This is the very same classic issue the Microsoft included in Windows long time ago, when upgrading the CPU. Why? Because they calculated the serial number based on what CPU and motherboard that was used, together with the product key. Eventually, after a number of computer owners complained about suddenly having a invalid license, Microsoft was forced to exclude the CPU in the calculation.

Checked the rest of my computers and found that the same issue apply to computer ID's: 994786 & 951917, 896361 & 990997 and 1038906 & 990631.
Technically, changing/upgrading OS should not matter either, so there are more examples ...

---

[ Ultra 9 285K + i9-14900K + i7-11700K + i9-10900K + E5-2697v4 + E5-2680v4 + E5-2630Lv4 + various Core gen. 3-8 | RTX A5000 + RTX A4000 + RTX A2000 | Lubuntu 22.04 + 24.04 ]

Now something happened, as when trying to merge, both mentioned computers are considered as one. Wrong.

---

[ Ultra 9 285K + i9-14900K + i7-11700K + i9-10900K + E5-2697v4 + E5-2680v4 + E5-2630Lv4 + various Core gen. 3-8 | RTX A5000 + RTX A4000 + RTX A2000 | Lubuntu 22.04 + 24.04 ]

"Incompatible" from BOINC's point of view isn't the same as from motherboard's point of view, it simply means, that it's not the same (BOINC doesn't care about what CPUs your motherboard supports, it doesn't know actually anything about it). Even when going from for example Windows 7 to Windows 10 on the same hardware BOINC will tell you, that the OS is "incompatible", although it obviously is compatible and runs on it. But it's a different OS.

In the future simply keep your BOINC data dir, than you can replace whatever parts you want or change the OS to whatever you want (in this case perhaps reset every project to delete applications first, in particular when moving from Windows to Linux or so) and BOINC won't care about it, even if you change the hardware completely and upgrade the OS.

---

If so, then this issue wouldn't exist, but it does ... Are you working at Microsoft? That would explain your answer ... Incompatible means that it doesn't work. Changing the meaning of words is a bad strategy.

When changing the OS and/or the CPU (memory, disks ...), technically it is still the same computer. Valid when I professionally started with computer hardware back in 1986 and still is today. Changing to a completely different motherboard, but keeping the rest, then it is a different computer.

I have been saving the BOINC data directory almost since I started with it back in Jan 2004, when I have done any changes to the hardware, like disks or major OS upgrades. Works with Windows 7, Lubuntu 18.04/20.04/22.04, but not with 24.04. In the latest version, all the data is wiped clean, regardless if it is put there before installing BOINC or after. In most of my computers since 10-11 years ago, I keep BOINC data on a separate disk and in Lubuntu, I map the disk into the regular location (/var/lib/boinc-client/). When I was still using Windows, I changed the path in the configuration file of concern. (Learned this the hard way due to all regular Windows crashes ...) If a crash occur, most often due to bad updates, it is a quick procedure with Lubuntu to reinstall everything from scratch and be up and running within 5-10 minutes, depending on the hardware.

---

[ Ultra 9 285K + i9-14900K + i7-11700K + i9-10900K + E5-2697v4 + E5-2680v4 + E5-2630Lv4 + various Core gen. 3-8 | RTX A5000 + RTX A4000 + RTX A2000 | Lubuntu 22.04 + 24.04 ]

Are you working at Microsoft? That would explain your answer ... Incompatible means that it doesn't work.

This has nothing to do with Windows or Microsoft, the BOINC devs decided to call it that way and they decided, what's the same computer and what's not.

I have been saving the BOINC data directory almost since I started with it back in Jan 2004, when I have done any changes to the hardware, like disks or major OS upgrades. Works with Windows 7, Lubuntu 18.04/20.04/22.04, but not with 24.04. In the latest version, all the data is wiped clean, regardless if it is put there before installing BOINC or after.

That's more than weird, but in this case you better ask in BOINC forums, you will more likely get an answer there than here.

---

Relating to Microsoft was due to how you responded and you have definitely not provided an answer. At best, guesses. That's weird, if anything ...

This is not BOINC related, as this only occur with Milkyway@home. Not at the other projects I'm involved in ... (Astroids@home, PrimeGrid, Einstein@home)

---

[ Ultra 9 285K + i9-14900K + i7-11700K + i9-10900K + E5-2697v4 + E5-2680v4 + E5-2630Lv4 + various Core gen. 3-8 | RTX A5000 + RTX A4000 + RTX A2000 | Lubuntu 22.04 + 24.04 ]