There are purposes for it, but with the power it would use for basic tasks, I think it is better recycled.

Total e-waste and a power draw (almost constant 95W). Even a Raspberry Pi 4 Model B can beat it to oblivion:

https://browser.geekbench.com/v6/cpu/compare/6390478?baseline=5583060

Take the intestines out and make a flower box.

A space heater.

You can buy a significantly more powerful and power efficient device for less than $100. It’s not really useful for anything besides nostalgia imo.

I wouldn’t run it as a router due to its high power consumption, but it would be a fine computer for retro gaming for games up until ~2005 if you add a graphics card.

Pentium D processors are pretty power hungry, so factor that into your thoughts. Also make sure you put a modern OS on it that is getting security updates. It probably has Win XP or Vista installed which isn’t safe to connect to any network.

It should work fine as a router as long as you don’t enable any of the packet inspection features. For basic routing and firewalling for a home network it should be plenty powerful. I would personally put a small SATA SSD in it as the main drive and ditch the 90GB HDD.

As an additional idea, if you put a larger SATA drive or two into it you could make it a NAS.

Keep the case and put a modern PC inside to make it a sleeper PC. Drill speed holes in the side for extra airflow that your computer will desperately need.

E-waste

• https://www.intel.com/content/www/us/en/products/sku/27512/intel-pentium-d-processor-820-2m-cache-2-80-ghz-800-mhz-fsb/specifications.html
• https://browser.geekbench.com/processors/intel-pentium-d-820-915-920
• https://www.cpu-world.com/benchmarks/Intel/Pentium_D_820.html
• https://en.wikipedia.org/wiki/Pentium_D
• https://pcper.com/2005/06/intel-pentium-d-820-2-8-ghz-dual-core-review/16/

If you switch the HDD for a pair of SDD (one storage, one swap), it would be somewhat useable. Better to increase the amount of RAM if possible. If I remember correctly, 2-4 GB of RAM was not uncommon at this time period. Although NixOS or a really light Debian install might be able to stay within that amount of RAM. So yea, I think it’s feasible.

Good Idea? Perhaps not so much. That proc has a TDP of 95W. Haven’t found anything on it’s idle power draw, but I’d guess that that system would have a fairly heavy power draw. The slow speed of the processor and low amount of RAM would probably limit the amount of traffic you could put through it. Additionally, the age of the components would probably cause reliability issues.

Generally I like to tell folks to use what they have. Repurposing old hardware is better for the environment and usually the wallet, but this system would probably would not be my first, second or even third choice for any workload. I haven’t found a benchmark comparing the two, but I think a Pi3 would probably run dead even with this system at a far lower power draw. Although the Pi3’s ethernet does run on it’s USB bus (I think), along with it’s storage, so that would slow it down for this workload. If you wanted to run traffic faster, I would probably look into the used micro PC market at the $75-$150 USD price point. This system is old enough to vote. Something merely 10 years old would be considerably faster.

Birds’ nest.