IBM was one of the many companies that acted as a second source for Intel. These chips are identical to Intel 80286s.
Unlike the other second sources, IBM was allowed to continue producing 386 and 486 chips under license. The IBM chips are internally identical to the Intel parts, but are frequently found in an unusual aluminium body PGA packaging (often soldered to a circuit board).
IBM's agreement with Intel not only allowed them to act as a second source, but also to make modifications to the CPU cores so long as they were sold as part of a complete system. This resulted in the 386SLC, which was essentially a 386SX with 8kb internal cache and i486 instructions. It was initially used in low power applications (like IBM laptops), but found its way into desktop systems as well. Despite being handicapped with a 16-bit external bus, the performance was generally excellent. These chips were only available in pqfp. None of the chips in this family used integrated FPUs.
486DLC2 (Blue Lightning)/486SLC2
More or less the same story as the 386SLC, but with 16kb internal cache and-clock doubling. IBM now produced a 386DX bus compatible 32-bit version as well (486DLC2). The DLC performed about as well as a full blown Intel 486, except in floating point operations, which is why it was referred to internally as "Blue Lightning". These chips were also successful in both portable and desktop applications. They have nothing to do with the Cyrix chips that bear the same model names as they are based on Intel cores.
486DLC3 (Blue Lightning)/486SLC3
These chips were the first x86 designs to make use of clock tripling. Otherwise they are identical to the SLC2/DLC2. It was around the time these chips appeared that IBM started selling them in standard AT motherboards and even supplying them to 3rd party manufacturers of upgrade modules. While good performers, they only became available to PC enthusiasts as the 486 was becoming obsolete (1994-1995). However, at the time they were an excellent bargain and could breathe new life into older systems when used as upgrade chips.
Identical to Intel 486DX (33MHz) and DX2 (50,66MHz) respectively
486DX2 Blue Lightning
After IBM's contract with Intel ended, IBM started acting as a second source for Cyrix. This was the first chip produced under the agreement. Although IBM reused the "Blue Lightning" brand on these chips, they are actually just standard Cyrix DX2s. Available in 50, 66 and 80MHz parts.
Identical to Cyrix DX4s with better quality control. Available in 75 and 100MHz parts.
Identical to Cyrix 5x86 but with better quality control and lower voltage ratings (3.3V vs 3.6V for Cyrix parts). They are easily identifiable by their blue heatsinks. Unlike the Cyrix and It'sST variants, it is not believed IBM ever produced any 5x86 chips with 4X multiplier support.
Identical to Cyrix parts but with IBM branding. The relationship between Intel and Cyrix broke down mid 1997 when Cyrix was purchased by National Semiconductor. Despite this IBM continued as a fabrication facility for Cyrix chips until the end of 1998. IBM did not produce any of the Cyrix chips using the MII branding.