I was running Einstein@home and Milkyway@home tasks on my GPU successfully until some weeks ago, but now the downloaded tasks sit with a message about GPU missing. As you'll see from the log below, BOINC manager shows messages indicating that the applications use OpenCL but it's not supported.

Non-GPU tasks for other projects run OK.

I've looked through several threads with similar symptoms, and tried:

1) NVIDIA drivers downloaded from the NVIDIA website, with clean install and reboot each time: 388.13, 388.43, 391.01, 391.24, 391.35, (a few auto updates in between), and the latest 397.64; all -desktop-win10-64bit-international-whql.exe

2) Renamed c:\windows\system32\OpenCL.dll before clean install of 388.43 to make sure it was indeed replaced.

3) Uninstalled drivers using Device Manager, rebooted and reinstalled from downloaded file (forget which version now).

clinfo sits for a few moment, and returns an empty log. GPU-Z shows CUDA supported, OpenCL not supported.

I run BOINC manager as a standard user (not admin).

I've run out of trouble-shooting ideas.......

19/05/2018 11:16:21 PM | | Starting BOINC client version 7.8.3 for windows_x86_64
19/05/2018 11:16:21 PM | | log flags: file_xfer, sched_ops, task
19/05/2018 11:16:21 PM | | Libraries: libcurl/7.47.1 OpenSSL/1.0.2g zlib/1.2.8
19/05/2018 11:16:21 PM | | Data directory: F:\ProgramData\BOINC
19/05/2018 11:16:21 PM | | Running under account <redacted>
19/05/2018 11:16:22 PM | | CUDA: NVIDIA GPU 0: GeForce GTX 1070 (driver version 388.13, CUDA version 9.1, compute capability 6.1, 4096MB, 3558MB available, 6707 GFLOPS peak)
19/05/2018 11:16:22 PM | | App version needs OpenCL but GPU doesn't support it
19/05/2018 11:16:22 PM | Einstein@Home | Application uses missing NVIDIA GPU
19/05/2018 11:16:22 PM | | App version needs OpenCL but GPU doesn't support it
19/05/2018 11:16:22 PM | Milkyway@Home | Application uses missing NVIDIA GPU
19/05/2018 11:16:22 PM | | Host name: <redacted>
19/05/2018 11:16:22 PM | | Processor: 8 GenuineIntel Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz [Family 6 Model 158 Stepping 9]
19/05/2018 11:16:22 PM | | Processor features: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss htt tm pni ssse3 fma cx16 sse4_1 sse4_2 movebe popcnt aes f16c rdrandsyscall nx lm avx avx2 vmx smx tm2 pbe fsgsbase bmi1 hle smep bmi2
19/05/2018 11:16:22 PM | | OS: Microsoft Windows 10: Professional x64 Edition, (10.00.17134.00)
19/05/2018 11:16:22 PM | | Memory: 15.95 GB physical, 18.33 GB virtual
19/05/2018 11:16:22 PM | | Disk: 3.64 TB total, 3.00 TB free
19/05/2018 11:16:22 PM | | Local time is UTC +12 hours
19/05/2018 11:16:22 PM | | VirtualBox version: 5.1.26
19/05/2018 11:16:22 PM | | Config: don't compute while MovieStudioPlatinum140.exe is running
19/05/2018 11:16:22 PM | | Config: don't use GPUs while javaw.exe is running
19/05/2018 11:16:22 PM | | Config: don't use GPUs while MinecraftLauncher.exe is running
19/05/2018 11:16:22 PM | | Config: use all coprocessors
19/05/2018 11:16:22 PM | Einstein@Home | URL http://einstein.phys.uwm.edu/; Computer ID 12605275; resource share 100
19/05/2018 11:16:22 PM | Milkyway@Home | URL http://milkyway.cs.rpi.edu/milkyway/; Computer ID 752343; resource share 100
19/05/2018 11:16:22 PM | Rosetta@home | URL http://boinc.bakerlab.org/rosetta/; Computer ID 3290572; resource share 50
19/05/2018 11:16:22 PM | World Community Grid | URL http://www.worldcommunitygrid.org/; Computer ID 4176299; resource share 100
19/05/2018 11:16:22 PM | Rosetta@home | General prefs: from Rosetta@home (last modified 03-Feb-2018 14:30:16)
19/05/2018 11:16:22 PM | Rosetta@home | Computer location: home
19/05/2018 11:16:22 PM | | General prefs: using separate prefs for home
19/05/2018 11:16:22 PM | | Reading preferences override file
19/05/2018 11:16:22 PM | | Preferences:
19/05/2018 11:16:22 PM | | max memory usage when active: 9802.71 MB
19/05/2018 11:16:22 PM | | max memory usage when idle: 12253.38 MB
19/05/2018 11:16:23 PM | | max disk usage: 200.00 GB
19/05/2018 11:16:23 PM | | max CPUs used: 1
19/05/2018 11:16:23 PM | | suspend work if non-BOINC CPU load exceeds 55%
19/05/2018 11:16:23 PM | | (to change preferences, visit a project web site or select Preferences in the Manager)
19/05/2018 11:16:23 PM | Rosetta@home | Task M1BLS9_PF03087_0.7_domain1_bnd10_aivan_SAVE_ALL_OUT_03_09_569072_127_0 is 20.17 days overdue; you may not get credit for it. Consider aborting it.
19/05/2018 11:56:23 PM | Milkyway@Home | work fetch resumed by user
19/05/2018 11:56:24 PM | Milkyway@Home | Sending scheduler request: To fetch work.
19/05/2018 11:56:24 PM | Milkyway@Home | Requesting new tasks for NVIDIA GPU
19/05/2018 11:56:30 PM | Milkyway@Home | Scheduler request completed: got 0 new tasks
19/05/2018 11:57:46 PM | Rosetta@home | General prefs: from Rosetta@home (last modified 03-Feb-2018 14:30:16)
19/05/2018 11:57:46 PM | Rosetta@home | Computer location: home
19/05/2018 11:57:46 PM | | General prefs: using separate prefs for home
19/05/2018 11:57:46 PM | | Reading preferences override file
19/05/2018 11:57:46 PM | | Preferences:
19/05/2018 11:57:46 PM | | max memory usage when active: 9802.71 MB
19/05/2018 11:57:46 PM | | max memory usage when idle: 12253.38 MB
19/05/2018 11:57:46 PM | | max disk usage: 200.00 GB
19/05/2018 11:57:46 PM | | Number of usable CPUs has changed from 1 to 2.
19/05/2018 11:57:46 PM | | max CPUs used: 2
19/05/2018 11:57:46 PM | | suspend work if non-BOINC CPU load exceeds 55%
19/05/2018 11:57:46 PM | | (to change preferences, visit a project web site or select Preferences in the Manager)
19/05/2018 11:57:50 PM | World Community Grid | Sending scheduler request: To fetch work.
19/05/2018 11:57:50 PM | World Community Grid | Requesting new tasks for CPU
19/05/2018 11:57:53 PM | World Community Grid | Scheduler request completed: got 2 new tasks
19/05/2018 11:57:56 PM | World Community Grid | Started download of oet1.xZAGP-OM_rig.pdbqt
19/05/2018 11:57:56 PM | World Community Grid | Started download of fdfe28822b0d4d8bb16ce8e3fc1d103b.job
...
19/05/2018 11:58:04 PM | World Community Grid | Finished download of 1d2a99ff40a37a80334ee030e9240c4b.zip
19/05/2018 11:58:04 PM | World Community Grid | Finished download of 393c710b48e82c218b7b38a63efd4dcf.pdbqt
20/05/2018 12:02:59 AM | Milkyway@Home | Sending scheduler request: To fetch work.
20/05/2018 12:02:59 AM | Milkyway@Home | Requesting new tasks for NVIDIA GPU
20/05/2018 12:03:01 AM | Milkyway@Home | Scheduler request completed: got 0 new tasks

Thanks for any suggestions.

SOLVED, but in a way I didn't expect. I'll leave this post here so others know to try it.

I enabled the on-board Intel GPU, downloaded and installed the relevant driver from Microsoft (win64_24.20.100.6025.exe), and rebooted. Now OpenCL is supported on the NVIDIA card (log follows).

The log identifies both GPUs as index 0 - don't know whether this means anything. Task Manager shows them with indices 0 (Intel) and 1 (GTX 1070).

I'll post again if disabling the on-board GPU or installing the latest NVidia drivers break OpenCL again. What I suspect is that turning on the on-board GPU triggered an update of something, or there was a relevant update in the Windows drivers for the i7 chip...just a guess.

--

20/05/2018 12:34:36 AM | | Starting BOINC client version 7.8.3 for windows_x86_64
20/05/2018 12:34:36 AM | | log flags: file_xfer, sched_ops, task
20/05/2018 12:34:36 AM | | Libraries: libcurl/7.47.1 OpenSSL/1.0.2g zlib/1.2.8
20/05/2018 12:34:36 AM | | Data directory: F:\ProgramData\BOINC
20/05/2018 12:34:36 AM | | Running under account <redacted> (Admin)
20/05/2018 12:34:37 AM | | CUDA: NVIDIA GPU 0: GeForce GTX 1070 (driver version 388.13, CUDA version 9.1, compute capability 6.1, 4096MB, 3558MB available, 6707 GFLOPS peak)
20/05/2018 12:34:37 AM | | OpenCL: NVIDIA GPU 0: GeForce GTX 1070 (driver version 388.13, device version OpenCL 1.2 yay! CUDA, 8192MB, 3558MB available, 6707 GFLOPS peak)
20/05/2018 12:34:37 AM | | OpenCL: Intel GPU 0: Intel(R) HD Graphics 630 (driver version 24.20.100.6025, device version OpenCL 2.1 NEO, 6506MB, 6506MB available, 221 GFLOPS peak)
20/05/2018 12:34:37 AM | | OpenCL CPU: Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz (OpenCL driver vendor: Intel(R) Corporation, driver version 7.6.0.698, device version OpenCL 2.1 (Build 698))
20/05/2018 12:34:37 AM | | Host name: <redacted>
20/05/2018 12:34:37 AM | | Processor: 8 GenuineIntel Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz [Family 6 Model 158 Stepping 9]
20/05/2018 12:34:37 AM | | Processor features: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss htt tm pni ssse3 fma cx16 sse4_1 sse4_2 movebe popcnt aes f16c rdrandsyscall nx lm avx avx2 vmx smx tm2 pbe fsgsbase bmi1 hle smep bmi2
20/05/2018 12:34:37 AM | | OS: Microsoft Windows 10: Professional x64 Edition, (10.00.17134.00)
20/05/2018 12:34:37 AM | | Memory: 15.88 GB physical, 18.26 GB virtual
20/05/2018 12:34:37 AM | | Disk: 3.64 TB total, 3.00 TB free
20/05/2018 12:34:37 AM | | Local time is UTC +12 hours
20/05/2018 12:34:37 AM | | VirtualBox version: 5.1.26
20/05/2018 12:34:37 AM | | Config: use all coprocessors
20/05/2018 12:34:37 AM | Einstein@Home | URL http://einstein.phys.uwm.edu/; Computer ID 12605275; resource share 100
20/05/2018 12:34:37 AM | Milkyway@Home | URL http://milkyway.cs.rpi.edu/milkyway/; Computer ID 752343; resource share 100
20/05/2018 12:34:37 AM | Rosetta@home | URL http://boinc.bakerlab.org/rosetta/; Computer ID 3290572; resource share 50
20/05/2018 12:34:37 AM | World Community Grid | URL http://www.worldcommunitygrid.org/; Computer ID 4176299; resource share 100
20/05/2018 12:34:37 AM | Rosetta@home | General prefs: from Rosetta@home (last modified 03-Feb-2018 14:30:16)
20/05/2018 12:34:37 AM | Rosetta@home | Computer location: home
20/05/2018 12:34:37 AM | | General prefs: using separate prefs for home
20/05/2018 12:34:37 AM | | Reading preferences override file
20/05/2018 12:34:37 AM | | Preferences:
20/05/2018 12:34:37 AM | | max memory usage when active: 9759.51 MB
20/05/2018 12:34:37 AM | | max memory usage when idle: 12199.38 MB
20/05/2018 12:34:37 AM | | max disk usage: 200.00 GB
20/05/2018 12:34:37 AM | | max CPUs used: 2
20/05/2018 12:34:37 AM | | suspend work if non-BOINC CPU load exceeds 55%
...
20/05/2018 12:34:52 AM | Milkyway@Home | Sending scheduler request: To fetch work.
20/05/2018 12:34:52 AM | Milkyway@Home | Requesting new tasks for NVIDIA GPU and Intel GPU
20/05/2018 12:34:54 AM | Milkyway@Home | Scheduler request completed: got 1 new tasks
20/05/2018 12:34:56 AM | Milkyway@Home | Started download of parameters-21-4s-NoConstraintsWithDisk.txt

What you should also do is set Windows Update not to update your device drivers, as else, even when you install drivers from Nvidia.. if Windows deems these not new enough it'll immediately reinstall its own drivers, that lack the OpenCL component. OpenCL is a unified standard, but I wouldn't rely on the Intel OpenCL component to correctly drive the Nvidia GPU.

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3) Uninstalled drivers using Device Manager, rebooted and reinstalled from downloaded file (forget which version now).

Did you reboot the PC after that? If GPU-Z doesn't detect OpenCL then BOINC won't either.