AMD FX-8100 socket: AM3+

What the FX-8100 is

AMD FX-8100 is an eight core Zambezi processor that AMD released in October 2011 for system builders, with boxed parts dated October 30. It uses the Bulldozer core design on a 32 nm process, running at 2.8 GHz base with Turbo Core to 3.7 GHz. The chip holds four Bulldozer modules with eight threads, 8 MB of L2 with 2 MB per module, and 8 MB of shared L3. Power is 95 W. Availability centered on integrators and OEMs with limited retail against the 8120 and 8150, so retailer confirmation matters for used buys. The box carries part number FD8100WMW8KGU. The Orochi die holds about 1.6 billion transistors on 319 mm², with 16 KB of L1 data per core plus 64 KB of L1 instructions per module. The unlocked multiplier spans 4x to 18.5x on a 200 MHz reference clock.

Eight threads at modest clocks cover threaded home work inside a 95 W budget. Turbo Core 2.0 lifts half loaded work to 3.7 GHz while full loads sit at 3.1 GHz. The 600 MHz turbo span covers both all core throughput and single thread bursts. The unlocked multiplier allows tuning on 990FX boards.

Towers pair it with 970 or 990FX boards, 8 GB of DDR3 and a discrete card. The 3.7 GHz maximum turbo leads the 95 W eight core range for single thread bursts. Fixed 2.8 GHz base clocks with turbo headroom suit multitasking without tuning. The How to find your CPU socket type guide shows how to confirm the socket.

Socket and motherboard compatibility

The FX-8100 drops into AM3+ on 9 series boards. The 942-pin socket accepts 940-pin AM3+ chips and 938-pin AM3 chips. AM3+ chips never fit AM3 boards. On AM3+ boards only DDR3 works, since no AM3+ board wires DDR2 slots. Check the maker CPU list for the exact board BIOS.

Power at 95 W suits standard tower boards. The 970 chipset covers single card builds while 990FX suits two card rigs. Southbridge chips SB950 or SB920 handle SATA and USB, with AMD OverDrive tuning software. The Socket vs chipset: what decides whether a CPU works guide covers AMD pairing rules.

Memory, PCIe and cooling

Memory support is DDR3 up to 1866 MT/s, two channels, up to four DIMMs. Two matched modules feed eight threads. Boards with four DIMM slots reach 16 GB with matched kits for eight threads. HyperTransport 3.0 links tie the CPU to the chipset at up to 5200 MT/s.

PCI Express slots come from the 9 series chipset with PCIe 2.0. A mainstream card of the era pairs without waste.

Cooling follows the 95 W rating with a stock heatsink or tower cooler.

Upgrade paths

On Socket AM3+ the FX-8100 can move to faster eight core Zambezi or Vishera parts on the same board. Memory, storage and the graphics card carry over. A faster eight core step is the FX-8120 class on the same socket. Vishera eight core parts add efficiency on the same DDR3 DIMMs where the BIOS lists them.

A platform move to DDR4 sockets needs a new board and RAM. The AM3+ tower keeps value for tuned duty where the unlocked multiplier still gives room past stock.