"Only so much" means that there is a limit. The sentence, "There's only so much that hardware manufactures can do." means that there is a limit to what hardware manufacturers can do. "There's only so much a person can take," implies that there is a limit to how much abuse, nonsense, etc. a person will allow before he/she loses his/her patience. The sentence "There is only so much you can remember" indicates that after being presented with a certain amount of information, a person is likely to forget any additional information presented over that limit.

Manufacturers can do some hardware, but they can't do more than a set amount. Manufacturers are limited in the amount of hardware they can do.

*manufacturers