VIA C3 800A socket: Socket 370

What the C3 800A is

The VIA C3 800A is an 800 MHz single-core desktop processor from September 2001. It runs one Centaur Ezra core at 800 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 with 16 million transistors. Power is rated at 8 W in a Socket 370 ceramic PGA package on a 133 MHz front side bus with a 6x multiplier at 1.35 V.

Ezra shrinks the earlier Samuel 2 base to 130 nm at the same 64 KB L2, which is why the 800A at 800 MHz runs cooler than 800 MHz Samuel 2 parts at 150 nm despite matching clocks. VIA placed the 800A in September 2001 with other Ezra parts such as the 866 MHz C3 866. The chip supports MMX, 3DNow and LongHaul power saving, with no SSE in this stepping.

Low clocks with a small cache and an 8 W envelope suit fanless value boards with SDRAM and integrated graphics. The 1.35 V core keeps heat down in tight cases with little airflow. That is why the 800A shipped in quiet office boxes with chipset video.

Socket and motherboard compatibility

The 800A fits Socket 370 value desktops with Ezra support. It needs a 370-pin board with a 133 MHz bus and a BIOS that lists VIA C3 Ezra parts. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Value SDRAM towers with VIA Apollo chipset paths are the natural match. Boards listing C3 800A accept the chip with a small 8 W cooler. Intel-only Socket 370 boards with no VIA microcode may refuse to boot, so the support list decides.

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. Value Apollo boards commonly carry two SDRAM sockets for 133 MT/s operation.

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 8 W. The 49.53 mm by 49.53 mm package needs light, even clip pressure.

Upgrade paths

On the same socket, a move to a C3 866T such as VIA C3 Processor 866T keeps the board and memory when the support list names it. The 866T adds 66 MHz at a similar power envelope, so the existing cooler stays ample. A Celeron 1000A such as Intel Celeron 1000A moves to Intel Tualatin cores with higher power and different microcode needs.

A move to Socket A or Socket 478 needs a new board and new memory rules. The Socket 370 page lists the Tualatin to Nehemiah range for planning. Note: the queue row for this part lists Nehemiah with 11 W from January 2003; this page uses the verified Ezra values of 800 MHz at 8 W from September 2001.