Pro computers do not require memory modules with heatsinks. Hard drives The Mac Pro had room for four internal 3.5" SATA-300 hard drives in four internal "bays". The hard drives were mounted on individual trays (also known as "sleds") by captive screws. A set of four drive trays was supplied with each machine. Adding hard drives to the system did not require cables to be attached as the drive was connected to the system simply by being inserted into the corresponding drive slot. A case lock on the back of the system locked the disks trays into their positions. The Mac Pro also supported Serial ATA solid-state drives (SSD) in the 4 hard drive bays via an SSD-to-hard drive sled adapter (mid-2010 models and later), and by third-party solutions for earlier models (e.g., by an adapter/bracket which plugged into an unused PCIe slot). Various 2.5-inch SSD drive capacities and configurations were available as options. The Mac Pro was also available with an optional hardware RAID card. With the addition of a SAS controller card or SAS RAID controller card, SAS drives could be directly connected to the system's SATA ports. Two optical drive bays were provided, each with a corresponding SATA port and an Ultra ATA/100 port. The Mac Pro had one PATA port and could support two PATA devices in the optical drive bays. It had a total of six SATA ports – four were connected to the system's drive bays, and two were not connected. The extra SATA ports could be put into service through the use of after-market extender cables to connect internal optical drives, or to provide eSATA ports with the use of an eSATA bulkhead connector. However, the two extra SATA ports were unsupported and disabled under Boot Camp. Expansion cards The 2008 model had two PCI Express (PCIe) 2.0 expansion slots and two PCI Express 1.1 slots, providing them with up to 300 W of power in total. The first slot was double wide and intended to hold the main video card, arranged with an empty area the width of a normal card beside it to leave room for the large coolers modern cards often use. In most machines, one slot would be blocked by the cooler. Instead of the tiny screws typically used to fasten the cards to the case, in the Mac Pro a single "bar" held the cards in place, which