You can always tell someone has a balanced and thought out take when their comment begins with what is essentially "you are wrong and I am right and there is no nuance or anything that I'm leaving out". (FYI obvious sarcasm).
Most people don't use RAM as their game cache and for very good reasons:
1) It's infeasible for anyone with large game libraries. It requires a shed load of expensive memory when you are talking about caching 8TB+ of games. People report 3-10% of a game's total size is cached. That's 400 GB of RAM at a conservative 5% per game. That is beyond the max RAM capacity of most consumer systems, let alone the abysmal timings and latency that would have. Heck even if it was possible you'd be dropping a cool 1.3K on that much memory, which defeats the purpose for the OP in the first place. If OP has that kind of money they could simply buy an 800GB optane which is actually a cache drive with 5x the sequential speeds and gets pretty darn close latency wise that isn't volitile and doesn't come with the drawbacks of a RAM Cache. Better yet, just get regular SSDs. The benefit of Optane is very minmal for games (I would know, I've compared my 800GB P5800X to my PCIe 5.0 T700 4TB).
2) Power loss or crashes result in data loss as the RAM Cache is volatile and only saved at certain times. Any memory errors will also cause corruption.
3) A RAM cache competes for memory bandwidth. Any performance demonstrated in benchmarks will be lower in gaming scenarios, as your RAM cache now has to compete with the game for bandwidth.
4) There is no practical benefit. People are not going to notice the difference between a game on RAM cache and a game on a decent SSD. Heck, there's hardly any benefit to anything faster than PCIe 3.0 in general.
In addition to the above, a RAM cache has great latency figures but poor sequential figures:
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In fact that sequential performance is piss poor and that will impact gaming performance. People who have tested a RAM Cache on a game reported no benefit so perhaps the two balance each other out.
The performance characteristics make sense though, DDR is optimized for random performance and latency. It's GDDR that's optimized for throughput.
RAM Caches aren't really suited nor beneficial to games in the vast majority of cases as the points above clearly illustrate. What works for you doesn't immediately work for others.
PrimoCache isn't primarily about RAM caching. That's certainly something you can do but not what most people use it for. The reason you don't see people with RAM Caches is because:
1) There is little to no benefit over SSDs.
2) RAM is expensive and it may not even be feasible depending on the size of your game library.
3) Larger amounts of RAM trade-off frequency and latency. Getting a hard to quantify benefit for very real disadvantage is not very appealing.
4) RAM Cache competes for memory bandwidth.
PrimoCache is far more commonly used to create an SSD cache for hard drives because that benefit is noticeable, easy to setup, and cheap. A 1TB SSD can be had for $70 - $80 and with that capacity you can cache a massive amount of data.
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