Catalina slow/unstable on a macbook pro 8,1

HI merrittr,

Your MacBook Pro isn't compatible with macOS Catalina, as noted here: macOS Catalina is compatible with these computers. To best resolve this, install the latest macOS version that is compatible with your Mac, which appears to be High Sierra: macOS High Sierra - Technical Specifications.

If needed, this article will help with reinstalling MacOS: How to reinstall macOS.

Although reinstalling macOS doesn't typically remove data from your Mac, to be safe, it would be best to create a backup: Back up your Mac.

Regards.

If you are experiencing slow performance or instability on your MacBook Pro 8,1 running Catalina, there are a few potential causes and solutions:

1. Insufficient RAM: Make sure that your MacBook Pro has enough RAM to run Catalina smoothly. If you are running low on RAM, consider upgrading to more RAM or closing unnecessary applications to free up memory.
2. Hard drive space: Make sure that your hard drive has enough free space to run Catalina. If your hard drive is full, consider deleting unnecessary files or upgrading to a larger hard drive.
3. Outdated software: Make sure that all of the software on your MacBook Pro is up to date. Outdated software can cause compatibility issues and slow performance.
4. Outdated hardware: Make sure that your MacBook Pro 8,1 is compatible with Catalina. If it's not, you might consider upgrading to a newer device or reinstalling an older version of the OS that is compatible with your device.
5. Malware or viruses: Make sure that your MacBook Pro is free of malware or viruses. If you suspect that your device is infected, run a full scan with a reputable anti-virus software.
6. Check for any updates for your device.
7. Try resetting the NVRAM or PRAM on your MacBook Pro.
8. Try booting your MacBook Pro in Safe mode to check if the problem is caused by any third-party software.

If you have tried all of these suggestions and the problem persists, it may be worth consulting with a professional or contacting the support team of Apple for further assistance.

[Link Edited by Moderator]

Most likely the laptop has a worn out or failing hard drive. Upgrading to an SSD will help to increase performance assuming everything else is Ok with the laptop.