After the launch of the 8086 and 8088 in respectively 1976 and 1978, Intel ended the XT era with the introduction of the 80286 CPU. The AT era had begun in 1982.

The 80286, or in short 286, had a 16 bit design and could address the enormous amount of 16 Megabytes of RAM. Unfortunately with that feature the processor was not backwards compatible with older processors and software that was written for these older CPU's. Because that backward compatibility was very important for the commercial success of the 286, Intel came up with a trick : Real-mode and Protected-mode. When a PC with a 286 booted, it booted in the Real-mode just like every XT would. In that mode the 286 could only address 1 Megabyte of RAM.
The software could then switch the processor in Protected-mode, the 286 could now address the full 16 Megabytes of RAM. Once the processor was switched to Protected-mode it could only switch back to real-mode by resetting the CPU, i.e. rebooting the PC. Looking back at that time and thinking of all those who had a 286, the software they ran, I think you could say that for the most people it was just a really fast XT.

When Intel launched the 286 it ran at a speed of 6 MHz, the speed was gradually increased to 8MHz, 10MHz, 12MHZ, 16MHZ, 20MHz and eventually 25MHz. Intel was still creating the micro processor market and availability would help doing just that. With enough processor available prices would drop and everyone could afford a PC. So Intel sold licenses to third party manufacturers like AMD, Siemens and HARRIS. They were allowed to clone the design and produce their own 286's.

Intel also developed a math coprocessor for the 286, the 287. Just like the 8087 the 287 accelerated floating point operations. Some special 286 CPU's were manufactured that had the possibility to mount the 287 on top. The 287-XL Floating Point Unit was the most advanced version of a 287. It used much less power than the original FPU and could also be used in combination with an 386SX. The 287-XLT was designed especially for use in notebooks.

The 286 appeared in CPGA, PLCC and CLCC packaging. Worth mentioning is that many 286 motherboards used a SIPP interface for the RAM instead of SIMM.

In 1985 Intel introduced the 386 at a speed of 16MHz and in those days the 286 was available at a speed of 25MHz. If you wanted performance you would be better off with an 286 at 25MHz, as it was faster than an 386 at 16MHz. You not only would have had a faster CPU but also to save yourself a lot of money as the 386 was very expensive in the beginning.