So I’m trying to create a race of alien that lives for 600 years but I need them to have the memory space for all that time. The human brain can hold approximately 300 years worth of memory and that is fine since humans don’t live over 100 very often. These aliens would have memory space for 600 years-1000 years and they wouldn’t have difficulty remembering things that happened 200 years ago. I figured I would also have time move faster to them to make sure they don’t go insane but just like I am 28 and remember something I did when I was 24; I want them to be 650 and remember something when they were 435. What would have to be different about their brains. They would be basically humanoid.
After reading the article I realize a large misconception you have. Instead of 300 years of memories it is 300 years of television shows. And that's a big difference. Humans don't remember everything they experience, more like 15-22% of events that have happened recently. Not the entire experience, but that it happened. But we'll ignore that. If you remember 22% of everything you ever do (which is incredibly unlikely) you will still be able to store around 1350 years in the human brain.
Data compression. Adjust compression ratios, compression/decompression speeds and data loss as needed.
There are a few riffs on this that come to mind.
Maybe these aliens have tiny brains and superb data compression/decompression, which is fine until they take some brain damage, at which point the poorly compressed, raw storage human brain is better. Or vice versa.
Maybe compression/decompression is actually what goes on in our brains when we're searching for old memories. And so aliens with superb compression ratios but slow decompression are a bit like old people; able to remember details from years ago, but not the best with where they left their spaceship keys.
Or their algorithm is lossy in a very specific way, leading to some common psychological blind spot or social weakness.