CBUS2 chipset

CBUS2 referred here is a core logic chipset used in the Sable/Lynx/Gamma systems (AlphaServers 2×00 and 2x00A). It is derived from CBUS used in the Cobra systems. In Tru64 code is it is referred as CBUS2; in Linux kernel code it is called T2.

The chipset consists of the top-level bus called CBUS, which is the main interconnect between the CPUs and the IO subsystem. CBUS has 8 nodes, from which 7 are pluggable and the 8th node is T2. T2 is the CBUS-to-PCI bridge.

Key features:

• The chipset is introduced in 1994
• Systems:
  • Sable family
    • AlphaServer 2000 EV4 – Demi-Sable
    • AlphaServer 2000 EV45 – Demi-Sable45
    • AlphaServer 2000 EV5x – Demi-Gamma-Sable
    • AlphaServer 2100 EV4 – Sable
    • AlphaServer 2100 EV45 – Sable45
    • AlphaServer 2100 EV5x – Gamma-Sable
  • Lynx family
    • AlphaServer 2000A EV45 – Demi-Lynx
    • AlphaServer 2000A EV5x – Demi-Gamma-Lynx
    • AlphaServer 2100A EV45 – Lynx
    • AlphaServer 2100A EV5x – Gamma-Lynx
• The number of CPUs: 1-4, EV4, EV45, EV5 or EV56
• Maximal memory: 2GB for 1-3 CPUs, 1GB for 4 CPUs.
• Supported OpenVMS: 6.1 and later
• Supported DEC OSF/1, Digital UNIX, Tru64: 2.0B or 3.0(??) and later

Names used by the operating systems:

• OpenVMS uses internal name CBUS. The CPU ROUTINES for Sable are 0902 and 0905 depending on the CPU. The CPU ROUTINES for Lynx are 1802 and 1805.
• Tru64 uses internal name CBUS2.
• Linux uses internal name T2.