Two Thunderbolt 2 ports (up to 20 Gbps).

512GB PCIe-based flash storage Configurable to 1TB flash storage.

256GB PCIe-based onboard flash storage (base model).

Configurable to 2.9GHz dual-core Intel Core i5 (Turbo Boost up to 3.3GHz) with 3MB shared 元 cache or 3.1GHz dual-core Intel Core i7 (Turbo Boost up to 3.4GHz) with 4MB shared 元 cache.

2.7GHz 2.7GHz dual-core Intel Core i5 processor (Turbo Boost up to 3.1GHz) with 3MB shared 元 cache.

Configurable to 1.3GHz dual-core Intel Core M processor (Turbo Boost up to 2.9GHz) with 4MB shared 元 cache.

1.2GHz dual-core Intel Core M processor (Turbo Boost up to 2.6GHz) with 4MB shared 元 cache.

Configurable to 1.3GHz dual-core Intel Core M processor (Turbo Boost up to 2.9GHz) with 4MB shared 元 cache (base model).

1.1GHz dual-core Intel Core M processor (Turbo Boost up to 2.4GHz) with 4MB shared 元 cache (base model).

Native resolution: 2560 by 1600 pixels (Retina).

Native resolution: 2304 by 1440 pixels (Retina).

Retina display: 13.3-inch (diagonal) LED-backlit display with IPS technology 2560-by-1600 resolution at 227 pixels per inch with support for millions of colors

Retina display: 12-inch (diagonal) LED-backlit display with IPS technology 2304-by-1440 resolution at 226 pixels per inch with support for millions of colors

8gb vs 16gb ram macbook pro retina