Intel Pentium II 266 Retail Box
The Pentium II was released May 7th 1997. It was an updated version of the immediate forerunning CPU, the Pentium Pro.
Forerunner – the Pentium Pro
The Pentium Pro was the first of the ‘x86’ CPUs, being optimised for running ‘proper’ 32bit operating systems. At the time that meant Microsoft Windows NT – standing for ‘New Technology’. NT was originally going to be the O/S that replaced all others. The idea was to wrap the user interface and execution engine around different back ends that would work arcoss a large variety of competing CPUs, such as the DEC Alpha RISC CPU, the MIPS Rxxxx series, the IBM POWER series, and of course the ARM Risc range. The Pentium Pro was pure 32bit, with an on-substrate full speed 256Kb,512Kb or 1Mb cache. The cache was of particular importance, since it wasn’t possible to make a whole CPU and the cache on one piece of silicon.
The above is a Pentium Pro missing the rear cover. Note that the cache on the right as a seperate piece of siicon.
Even though the chip and the cache were separate, they were close enough to each other electrically to allow the cache to work at the same speed as the chip for the first time; between 166 and 200Mhz in this case. The previous Pentium design had cache hosted on the motherboard, running at 50-66Mhz.
Having cache running this fast was obviously extremely helpful; however as it was, it was impossible for Intel to test the chip or the cache separately before they were integrated together into the chip itself. A flaw in either side meant scrapping the whole chip. This made the Pentium Pro very expensive to manufacture.
In the market place, the Pentium Pro tested out as working very well with pure 32bit code in Windows NT etc, however it did not perform anywhere near as well executing 16-bit code as was still quite prevalent in the Windows 95 and 98 range of operating systems. In fact, the earlier Pentium design was clock for clock better at 16bit, even though the cache was so much slower. The market was spilt, with Win 95/98 working in the ‘home’ market, for gamers and smaller businesses and Win NT being the de-facto operating system for networks and businesses. The Pentium Pro found in niche in the new and growing market of specialised server computers.
The Pentium II
The Pentium II was a fusion of x86 Pentium Pro technology and the best from the old Pentium range, namely MMX instructions and improved 16-bit code execution. It was made available as a side-mounting cartridge system rather than a more traditional chip with pins as had been the case with all older CPUs to that date.
The cartridge system aka ‘slot 1’ was put in place solely to solve the cache fabrication issues of the Pentium Pro. The cartridge consisted of a card, with the CPU and separate cache chips all mounted in once place. The cache chips were fabricated separately by a 3rd party, and ran at 1/2 the core clock speed. This solved the fabrication issues of the Pentium Pro.
