Add Run A Hardware Check as a mac til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_615 TILs and counting..._
+_616 TILs and counting..._
 
 ---
 
@@ -262,6 +262,7 @@ _615 TILs and counting..._
 - [List All The Say Voices](mac/list-all-the-say-voices.md)
 - [Require Additional JS Libraries In Postman](mac/require-additional-js-libraries-in-postman.md)
 - [Resizing Both Corners Of A Window](mac/resizing-both-corners-of-a-window.md)
+- [Run A Hardware Check](mac/run-a-hardware-check.md)
 
 ### MySQL
 

mac/run-a-hardware-check.md

@@ -0,0 +1,16 @@
+# Run A Hardware Check
+
+If your Mac is behaving in an odd way, there may be an issue with some piece
+of the hardware -- such as the RAM.
+
+You can perform a hardware check in order to chase down a diagnosis.
+
+- Shutdown your machine
+- Boot your machine
+- While it is booting, hold down the `d` key
+
+At this point, the machine should have booted into a special hardware check
+mode. Select your preferred language, the hardware check will be performed,
+and any issues will be reported.
+
+h/t Dillon Hafer