• PCI 2.2 compliant, 32-bit 3.3V PCI interface with 5V tolerant inputs
• Supports up to 5 PCI masters

Yes, the northbridge controls PCI. In this case, you can have up to five PCI master devices on a 33MHz, 32-bit PCI bus, which isn't shabby.

• Dynamic power down of SDRAM (CKE)
• Independent clock stop controls for CPU / SDRAM, AGP, and PCI bus
• PCI and AGP bus clock run and clock generator control
• VTT suspend power plane preserves memory data
• Suspend-to-DRAM and self-refresh power down
• Low-leakage I/O pads
• ACPI 1.0 and PCI Bus Power Management 1.1 compliant

The PM133 chipset has the power, or more to the point, knows how not to use it. Low-power modes are par for the course these days.

Drivers for major operating systems and APIs: [Windows 9x, Windows NT 4.0, Windows 2000, Windows 3.x, OS/2 2.1/3.0 (Warp), Linux, Direct3D, DirectDraw ƒnand DirectShow, OpenGL ƒnICD for Windows 9x, NT, and 2000

The only x86 operating systems we don't know if the PM133 supports are the BSDs and Solaris, neither of which we expect the average PM133 owner will want to use.