2.5.2 General z14 RAS features The z14 server includes the following RAS features: IBM z14 servers continue to deliver robust server designs through exciting new technologies,  hardening both new and classic redundancy. For more information, see Chapter 9, “Reliability, ava ilability, and serviceability” on page 363. GLYPH<SM590000> The z14 server provides a true N+1 cooling function for the radiator-cooled (air-cooled)  model and a true N+1 (fully redundant) cooling function for the water-cooled model.  GLYPH<SM590000> The power supplies for the z14 server are also based on the N+1 design. The second  power supply can maintain operations and avoid an unplanned outage of the system. GLYPH<SM590000> The IBM Z processors feature improved chip packaging (encapsulated chip connectors)  and use SER hardened latches throughout the design.  GLYPH<SM590000> An N+2 point-of-load (POL) power conversion redundancy, which protects the processor  from the loss of voltage because of POL failures. GLYPH<SM590000> An N+2 redundancy on the environmental sensors (ambient temperature, relative  humidity, air density$^{2}$, and corrosion). GLYPH<SM590000> Enhanced bus structure that uses integrated time domain reflectometry (TDR) technology. GLYPH<SM590000> PCIe service enhancements: – Mandatory end-to-end cyclic redundancy check (ECRC)  – Customer operation code separate from maintenance code – Native PCIe firmware stack that is running on the integrated firmware processor (IFP)  to manage isolation and recovery 2 The air density sensor measures air pressure and is used to control blower speed. 66  IBM z14 (3906) Technical Guide