VIA C3 Processor 866T socket: Socket 370

What the C3 Processor 866T is

The VIA C3 Processor 866T is an 866 MHz single-core desktop processor from September 2001. It runs one Centaur Ezra-T core at 866 MHz with no turbo, so 1 core gives 1 thread. Cache is 64 KB of L2 with 128 KB of L1 on a 130 nm process. Power is rated near 9.2 W in a Socket 370 ceramic PGA package on a 133 MHz front side bus with a 6.5x multiplier at 1.35 V.

Ezra-T keeps the Ezra cache layout while moving to copper interconnects, which is why the 866T at 866 MHz runs steady in warm cases where older 150 nm Samuel 2 parts throttle. VIA placed the 866T in September 2001 with the 800A and 900 MHz Ezra parts. The chip supports MMX, 3DNow and LongHaul power saving.

Sub-gigahertz clocks with a tiny cache and a 9 W envelope suit always-on Socket 370 boxes with SDRAM and no fan. The 1.35 V core sips power at idle with LongHaul enabled. That is why the 866T shipped in kiosk and terminal boards with integrated video.

Socket and motherboard compatibility

The 866T fits Socket 370 low-power desktops with Ezra-T support. It needs a 370-pin board with a 133 MHz bus and a BIOS that lists VIA C3 Ezra-T strings. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Kiosk and terminal boards are the natural match. Boards listing C3 866T accept the chip with a 9 W cooler. Boards that list only Intel Celeron strings may skip the VIA CPUID, so the support list revision matters.

Memory, PCIe and cooling

Memory is PC100 and PC133 SDRAM through the board chipset, matched to the board DIMM sockets. The CPU has no memory controller, so the chipset sets the type and speed. Terminal boards commonly run a single PC133 module for the 133 MHz bus.

A 133 MHz front side bus ties the CPU to the chipset, while AGP and PCI hang off the chipset. No PCIe lanes originate on the die. Cooling uses the Socket 370 lug clip with a cooler rated for 9 W. Low-profile blocks fit 1U and terminal cases with side airflow.

Upgrade paths

On the same socket, a move to a C3 Processor 1.0 such as VIA C3 Processor 1.0 keeps the board and memory when the support list names it. The 1.0 adds 134 MHz at a similar 10 W envelope, so the cooler carries over. A C3 800A such as VIA C3 800A drops 66 MHz at slightly lower power.

A move to Nehemiah C3 parts adds SSE and stronger floating point with a BIOS update. The Socket 370 page lists the Tualatin to Nehemiah range for planning.