After I wrote that the Hot Topics didn't require a subscription, it occurred to me that I should talk a bit about what areas of the site are restricted to subscribers and what is free.
We are a publication that is subscription based and there are various ways to get a subscription and this gain access to the restricted parts of CR. The two most common methods are that your institution (school or company) subscribes and you get access via IP validation. The second is that you have a personal membership to the ACM and a personal subscription to their portal. That will also get you access to most areas of CR.
The restriction on CR lies at the "bottom" or content level. You can navigate around the site, perform search and browse functions and get results that contain a snippet of the review (what we call the "partial review"). It's when you try to access the full review that you will be checked for a subscription. So most of the review content is restricted to subscribers.
But not all of it. As I have said, the hot topics essays are open to everyone and the reviews that are linked to from the sidebar of the essays are also free. When we post the essays we remove the restrictions from those reviews.
Other free reviews are the highlighted reviews - a new highlighted review (picked by the category editors) is posted each week and those are also available for everyone to read.