I have a Windows 10 machine with two video cards: an older GTX 660Ti and a new GTX 1080. When I connect to GPUGRID, the GTX 1080 runs tasks fine, but the GTX 660Ti generates immediate "Computation error" messages for every job with this same detail in the task list:

# GPU [GeForce GTX 660 Ti] Platform [Windows] Rev [3212] VERSION [80]
# SWAN Device 1 :
# Name : GeForce GTX 660 Ti
# ECC : Disabled
# Global mem : 2048MB
# Capability : 3.0
# PCI ID : 0000:03:00.0
# Device clock : 1045MHz
# Memory clock : 3004MHz
# Memory width : 192bit
# Driver version : r370_00 : 37306
#SWAN: FATAL: cannot find image for module [.nonbonded.cu.] for device version 300

But, the GTX 660Ti is in the valid cards list. One more thing: When I view my computers on the GPUGRID computer list, it shows:

[2] NVIDIA GeForce GTX 1080 (4095MB) driver: 373.6

instead of 1 GTX 1080 and 1 GTX 660Ti. PrimeGrid, Collatz Conjecture, and Folding@Home all work fine using both GPUs; it's only GPUGRID.

Any ideas? Thanks!

You cant mix this two generations in one pc. Pascal app doesn't work on 660.

Thanks for the info. Are all GPUGRID tasks Pascal tasks? Can I specify different types of tasks for different processors? What should I do to prevent my computer from wasting resources on GPUGRID's servers, causing my client to download tasks that will fail in a few seconds? Or should I just disconnect from GPUGRID?

Not sure what to do now.

Thanks for the info. Are all GPUGRID tasks Pascal tasks?

No. There's no such distinction. But if you have at least one Pascal card in a system, that system will use the new app, and that will make all tasks fail on the pre-Pascal cards. See this post (and thread).

Can I specify different types of tasks for different processors?

You can't.

What should I do to prevent my computer from wasting resources on GPUGRID's servers, causing my client to download tasks that will fail in a few seconds?

You have 2 options:
1. remove the older card
2. disable the older card in BOINC manager (in cc_config.xml)
copy the following to your clipboard:

notepad c:\ProgramData\BOINC\cc_config.xml

Press Windows key + R, then paste and press enter.
If you see an empty file, copy and paste the following text:

<cc_config>
  <options>
    <exclude_gpu>
      <url>www.gpugrid.net</url>
      <device_num>1</device_num>
      <type>NVIDIA</type>
      <app>acemdlong</app>
      <app>acemdshort</app>
    </exclude_gpu>
  </options>
</cc_config>

If your cc_config.xml already has an <options> section then you should insert the section between the <eclude_gpu> and the </eclude_gpu> tags (including both) right after the <options> tag.
Click file -> save and click [save].
If your BOINC manager is running, you should click Options -> read config files.
EDIT: Perhaps you should restart BOINC manager (stop the scientific applications upon exiting). The <type> and the <app> sections could be omitted, the value in the <device_num> section should be adapted to the given system.

Or should I just disconnect from GPUGRID?

It's not necessary.

Not sure what to do now.

I would disable the older card.

Thanks very much for taking the time to provide a detailed and helpful reply. I will do what you recommended.

It's too bad that this project's own documentation, located at:

https://www.gpugrid.net/forum_thread.php?id=2507

explicitly states that the GTX 660Ti is still supported when it apparently is not.

It would be fantastic if the programmers at GPUGRID would add code to the project so that it would send some kind of helpful and actionable message to the user when this happens, rather than simply display a cryptic and unhelpful "Computation error" message. It seems like that message appears (and perplexes people) often.

Again, I do appreciate the helpful replies that were kindly provided to my original question.

Thanks very much for taking the time to provide a detailed and helpful reply. I will do what you recommended.

You're welcome. See my EDIT for additional info.

It's too bad that this project's own documentation, located at:

https://www.gpugrid.net/forum_thread.php?id=2507

explicitly states that the GTX 660Ti is still supported when it apparently is not.

This GPU is supported only by the older app, the thing that is not supported is mixing Pascal GPUs with older GPUs in the same system.

It would be fantastic if the programmers at GPUGRID would add code to the project so that it would send some kind of helpful and actionable message to the user when this happens, rather than simply display a cryptic and unhelpful "Computation error" message. It seems like that message appears (and perplexes people) often.

Yep.