Intel Pentium III 866

The Intel Pentium III 866 is a single-core, single-thread desktop processor from Intel with a base clock of 866.00 MHz and no boost clock. It uses the P6 architecture, carries the codename Coppermine T, and is fabricated on Intel's 180 nm process with 44 million transistors on an 80 mm² die. Cache is an 8 KB L1 and a 256 KB L2, with no L3. The chip fits Intel Socket 370 and is rated at a 38W TDP. Released in May 2001, it is now end-of-life. In the database it sits at the 50th percentile of all CPUs, though its average benchmark score is 0 and its benchmark list is empty.

How It Compares

The nearestRivals array in the FACT PACK is empty. There are no rival CPUs named, no rival scores, and no deltaPct percentages to place against the Pentium III 866. A per-rival comparison would require data the pack does not contain. The empty array also means there is no deltaPct field to express a margin in either direction; the percentile is an absolute rank within the full CPU list, and it is the only comparable value in the record.

Interpreting the empty rivals list: when a database entry lacks competitor rows, the safest comparison is to the full CPU distribution rather than to any individual product. The 50th percentile in the FACT PACK is exactly such a distribution-level comparison, and it is a more conservative statement than any head-to-head delta would be.

The only positional signal is percentileVsAllCpus, set to 50. That is the median of the database's CPU sample: as many processors are recorded above it as below it. The comparative position is "middle of the field" rather than top or bottom. This is a real but modest statement; the processor is neither an outlier at the top nor a laggard at the bottom.

The avgBenchmarkScore of 0 and the empty benchmarks array reinforce the caveat. A 50th percentile with no underlying logged runs is an ordinal placement, not a measured performance level. The data does not permit a stronger claim.

Power and Thermals

The Pentium III 866 is rated at a 38W TDP. That figure defines the cooling class: a simple air cooler will suffice. Nothing in the pack suggests anything beyond mainstream cooling for this socket — no oversized heatsink, no liquid loop, no special mounting is indicated by a 38W envelope.

The 180 nm process, 44 million transistors, and 80 mm² die point in the same direction. The heat-producing area is compact, and the total dissipation is modest. With only 38W to move, a conventional Socket 370 cooler and a standard board can handle the load. The 180 nm process is a wide-node design; the 44 million transistors in 80 mm² give a measure of the integration scale. A 38W rating on that scale indicates a chip built for low power rather than high clock extremes.

The FACT PACK does not record temperatures, fan speeds, or cooler sizes. The thermal analysis is limited to the TDP, the process node, the transistor count, and the die size. All of these describe a light thermal load that should not challenge a typical desktop chassis.

Single-Thread vs Multi-Thread Behavior

The topology is 1 core and 1 thread. The chip cannot run more than one thread at any instant. The base clock of 866.00 MHz, with no boost clock listed, is the frequency that thread uses — there is no turbo state to lift performance for a short burst.

For single-threaded workloads, the 866.00 MHz clock is the first determinant, and the cache layout is the second. The 8 KB L1 and 256 KB L2 form the entire cache hierarchy, since no L3 is listed. The two cache levels are far apart in size, which suggests the 256 KB L2 carries the heavy lifting for working sets. A program that keeps its active data inside the 256 KB L2 has room to work; a program that overflows that 256 KB region must go to system memory. The pack gives no memory bus or memory bandwidth, so the cost of a cache miss cannot be measured from this data.

For multi-threaded workloads, the limit is the single thread. The operating system can interleave multiple processes onto that one thread, but there is no parallel execution and no second thread to absorb work. Software written to scale across cores would see exactly one logical processor.

The split tells a builder one thing: this CPU belongs on tasks where per-thread speed and cache fit matter, not on tasks that depend on thread count. The data shows no multi-thread advantage because there is no thread to spare.

FAQ

Q: What socket does the Intel Pentium III 866 use?

A: Intel Socket 370. The motherboard must provide that socket to accept the chip.

Q: How many cores and threads does it have?

A: 1 core and 1 thread, at a base clock of 866.00 MHz with no boost clock.

Q: What cache does it carry?

A: An 8 KB L1 cache, a 256 KB L2 cache, and no L3 cache.

Q: Does it have integrated graphics?

A: Integrated graphics is listed as "On certain motherboards (Chipset feature)". Graphics availability depends on the motherboard chipset, not on the CPU itself.

Q: Is the multiplier unlocked?

A: No. The multiplierUnlocked field is false, so the processor does not offer a configurable multiplier.

Q: What is the production status?

A: End-of-life. The release date is May 2001.

Benchmark Performance

The performance data is sparse. The benchmarks array is empty, the average benchmark score is 0, and the nearestRivals array is empty. There are no raw scores to compare and no deltaPct values from which to calculate percentage differences. A percentage comparison would require a rival score, and none is present. Because no measured score exists, the database cannot validate the 50th percentile against a real workload; the rank and the zero average are the entire numeric record.

The only performance-rank field is percentileVsAllCpus, with a value of 50. That is the median position in the database. It means the aggregate rank is exactly halfway: as much of the sample sits above it as below it. The average score of 0 does not change that rank, but it does mean the percentile stands alone as the only numeric benchmark summary.

What the benchmark section can affirm is the configuration behind that percentile: a 1-core, 1-thread CPU at 866.00 MHz, with an 8 KB L1 cache, a 256 KB L2 cache, no L3 cache, and a 38W TDP. Those parameters define the chip's performance class better than the empty score fields do. The 50th percentile places the part in the middle of the tracker; the 0 average leaves the performance magnitude undefined.

Platform and Compatibility

The processor uses the Intel Socket 370 interface. The market segment is Desktop and the production status is end-of-life, so the platform is no longer in active production.

Memory support is not specified. The fields for memorySupport, memoryBus, and memoryBandwidth are all null in the FACT PACK, so no RAM standard, memory bus, or bandwidth can be reported. The only memory-related fact is eccMemory: false, meaning ECC memory is not supported.

The pack has no PCIe information. There is no PCIe version, lane count, or slot topology, so the expansion capabilities of the platform cannot be analyzed from the available data. A builder would need to consult motherboard documentation for those details.

Integrated graphics exist only "On certain motherboards (Chipset feature)". Display output is a board-level decision; the CPU itself provides no graphics core.

Upgrade path: because the socket is Intel Socket 370, any compatible drop-in processor must use that same socket. The FACT PACK does not name other Socket 370 CPUs and lists no compatibility matrix. The locked multiplier (multiplierUnlocked: false) is the only frequency-related access point mentioned, and it rules out multiplier-based overclocking. The physical data — 180 nm process, 44 million transistors, an 80 mm² die — completes the platform picture. For a builder, the takeaway is that the socket fixes the board choice, the chipset decides graphics, and the CPU is at the end of its production life.