How do I make an HDD as fast as an SSD?

I have a really slow iMac that I bought 2 years ago. I've been so annoyed about how I have to wait for the rainbow circle to stop loading. I did some research and found out it's about the hard drive. My iMac had an HDD drive. I didn't want to buy an SSD so I thought why not do something to make the HDD as fast as an SSD.

Can you please help me on making an HDD as fast as an SSD?

Here are my imac specs

I'm afraid that's impossible. Your hard drive is essentially not much different from an old record turntable: it has spinning disks and a 'head' that writes or reads the magnetic stripe at a point on the wheel.

There are many different mechanical parts that all contribute limitations to the maximum possible speed.

Furthermore: it's a sealed unit, made in a factory. If there was some easy 'tweak' to make it as fast as an SSD, the manufacturers would have done it.

• SSD are designed like a car. HDD are trucks.
• You can’t make a truck operate like a car unless you buy a car and call it a truck.
• Diesel fuels most trucks and some cars (computer “fuel” is SATA interface and command set).
• Most cars run gas (NVMe).

You want a light car running on gas to get the best acceleration. Boot to the fastest SSD connected via NVMe controller for max performance and speed, there is no shortcut, especially with a truck response and SATA driving.

Some HDD add a layer of SSD and try to cache data similar to how Apple does Fusion drives (think nitrous oxide), but this doesn’t get you NVMe.

In the end, connect an SSD via thunderbolt if you need equivalent speeds to having an internal SSD on an iMac. Your iMac is capable of tens of thousands of io per second if you bring fast storage to it, internally or externally so your wish can be granted, just not with HDD.

Shop for NVMe over Thunderbolt is my advice.

• https://www.macworld.com/article/3276325/nvme-over-thunderbolt-killer-external-storage-with-caveats.html

If you want to make a hard drive run as fast as an SSD, install lots of RAM, and put the system to sleep rather than shutting it down when you're finished. If you've got enough RAM (in my experience, 64 GB is enough for a typical desktop), after a day or two of use, the parts of the disk that you normally use will be cached in memory, so the disk won't actually be accessed.

Note that it's considerably cheaper to get an SSD than it is to install enough RAM for this to work.