1) What CPU?
2) USB 3 or 2 on the external drive.
What others have discussed is true but running an older Celeron and an old spinning external drive on USB 2 is going to be a totally different experience then an 6th gen i5 and a newer 7200RPM external on USB3
-Dave
+1
When you use NVMe 4.0+ internal drives, the CPU becomes the 'bottleneck', especially towards the more recent blocks.
I recently downloaded the whole blockchain using a notebook (T480, i5 1.8GHz, 2TB NVMe 4.0, 64GB) and it took ~25 hours
to download the whole thing.
I saw CPU usage over 90% towards the end of the download, around the 2023 data.
Memory, network, and disk usage never went over 15%.
A kick-ass desktop with something like i9-13900K and NVMe 5.0 would probably take half a day to download the whole thing.