Intel Pentium

The Intel Pentium is the successor to the i486. It was released in 1993 and brought significant improvements with its P5 architecture such that it was twice as fast as a 486 at a given frequency like the 486 was in comparison to the 386. Pentium refers to the number 5 like in "pentagon" as it would have been i586 if they kept the same naming scheme as the i386 and i486. The first Pentiums were made with a 800 nm process and incorporated 3.1 millions transistors.

There are several versions of P5 based Pentiums:

The original Pentium was released with the Socket 4 and first available as 60 and 67 MHz parts. Parts up to 200 MHz were released later, on Socket 5 and 7.
The Pentium OverDrive, released in 1995 at 63 and 83 MHz, allowed to upgrade some Socket 2 or 3 i486s without changing the motherboard. Later Pentium OverDrive also appeared and allowed to upgrade older Pentiums, up to 167 MHz.
The Pentium MMX was released in 1997 and added the MMX instruction set to accelerate multimedia operations.
There are also various Pentiums for Mobile and Embedded Platforms. One can notably cite the Tillamook code named ones, which had parts up to 300 MHz. There is a Socket 7 267 MHz version that can easily be overclocked to 400 MHz, but it does not work on most Desktop motherboard.

Early Pentiums were affected by the famous FDIV Bug, and returned an incorrect result for some divisions. Intel initially did not take the problem seriously as the errors would indeed be negligible for most people, but due to the issue quickly becoming well known and causing negative press for them, Intel recalled these processors and replaced them on request.

The Pentium Pro, despite using the name Pentium, was based on a different architecture (P6) and released in 1995, before the Pentium MMX. The Pentium II suceeds the Pentium Pro as a P6 based processor and also adds the MMX instruction set.

Intel ABOXPCPU5V60 Box — A Sealed Box containing a Pentium 60 MHz for Socket 4 (PCPU5V60). Extremely Rare Box. Back.

A Sealed Box from the recall program, containing a FDIV Bug free replacement for an affected Socket 4 Pentium 67 MHz. Back.

Intel CBOX8050166SX950 Box — A Sealed Box containing a Pentium 60 MHz for Socket 4 (PCPU5V60). Extremely Rare Box. Back.

A Sealed Box from the recall program, containing a FDIV Bug free replacement for an affected Socket 4 Pentium 67 MHz. Back.

Intel A80501-60 SX753 — A 60 MHz Pentium for Socket 4 without Golden Heatsink, affected by the FDIV Bug (SX753). Bottom. Malaysia, 1993 Week 41.

A 60 MHz Pentium for Socket 4 with Golden Heatsink, affected by the FDIV Bug (SX835). Bottom. Malaysia, 1993 Week 51.

A 90 MHz Pentium for Socket 5 with Golden Heatsink, affected by the FDIV Bug (SX879). Bottom. Malaysia, 1993 Week 41.

A 100 MHz Pentium for Socket 5 without Golden Heatsink, unaffected by the FDIV Bug (SX963). Bottom. Malaysia, 1995 Week 12.

A 83 MHz Pentium OverDrive for upgrading Socket 2 and 3 i486s (SU014). Without Fan, Bottom. 1995 Week 46.

A Pentium MMX Mechanical Sample (not intended for sale) Socket 7. Usual Pentium MMX look like it, though Ceramic versions also exist. We tried to run it and it works normally! Bottom.

A 133 MHz Mobile Pentium, to be soldered on a Laptop Motherboard for example. Bottom, With Original Carrier. 1997 Week 47.

Intel A80501-60 SX835 — A 60 MHz Pentium for Socket 4 without Golden Heatsink, affected by the FDIV Bug (SX753). Bottom. Malaysia, 1993 Week 41.

A 60 MHz Pentium for Socket 4 with Golden Heatsink, affected by the FDIV Bug (SX835). Bottom. Malaysia, 1993 Week 51.

A 90 MHz Pentium for Socket 5 with Golden Heatsink, affected by the FDIV Bug (SX879). Bottom. Malaysia, 1993 Week 41.

A 100 MHz Pentium for Socket 5 without Golden Heatsink, unaffected by the FDIV Bug (SX963). Bottom. Malaysia, 1995 Week 12.

A 83 MHz Pentium OverDrive for upgrading Socket 2 and 3 i486s (SU014). Without Fan, Bottom. 1995 Week 46.

A Pentium MMX Mechanical Sample (not intended for sale) Socket 7. Usual Pentium MMX look like it, though Ceramic versions also exist. We tried to run it and it works normally! Bottom.

A 133 MHz Mobile Pentium, to be soldered on a Laptop Motherboard for example. Bottom, With Original Carrier. 1997 Week 47.

Intel Pentium Keychain — A Keychain with a Pentium 80501 Die.

Two Pentium 80502 Dice.

A 8" Silicon Wafer of Intel 80502 (80P54C) Chips. More Views: 2, 3a, 3b, 3c, 3e, 3f, 3g, 3h, 3i.

A Blank Pentium A80502.

Operating System Support

A Pentium will by itself not prevent any x86 Windows until 7 from running. Windows Me, 2000 and XP officially require a Pentium, though the first two can actually work on a 486 while the requirement is absolute for XP, that can however run on a 486 platform with a Pentium OverDrive. Windows Vista and 7 officially require a 800 and 1 GHz CPU, but can actually work on the original Pentium regardless of the frequency.
- Vista and 7 however require the motherboard to have some ACPI compliance, and such Sockets 4 and 5 boards might not exist. A non compliant motherboard will cause a Blue Screen at the start of the installation or during boot with the "The BIOS in this system is not fully ACPI compliant" message and 0x000000A5 code). We are not aware of any way to bypass the ACPI requirement.
- There should be 384 MiB of RAM to be able to install them, though it is possible to subtract some RAM once installed.
- Aero requires a Pentium MMX, otherwise the Desktop Window Manager will crash. However, many unclear factors might also make DWM crash even with a Pentium MMX, we actually thought for years that it was not possible to have Aero on Pentium MMX until it surprisingly worked when we tried again!
  - Interestingly, with an unsupported CPU, the taskbar actually appears like Aero were working fine for a few instants with a black background, before DWM crashes and the wallpaper is loaded.
  - It is possible that the crash is due to the GPU driver rather than the Aero implementation itself, which might actually by itself work with a non MMX Pentium. We could make Aero work with a GeForce 6200 but not a Radeon 9500, which will only work with a later processor.
- The Windows Experience Index assessment will stop quickly after it started, claiming to be unable to complete, this time also with a Pentium MMX.
- The FDIV Bug cannot be observed with the Windows Vista or 7's built-in Calculator as it does not use the FPU, but a failing operation can be entered in PowerShell and will provide the incorrect result.
- Some later Windows 7 updates will break support since they require SSE2.
Windows 8 and later are no gos as it is not even possible to install them on Pentium IIIs.
The original P5 is still supported by the Linux Kernel, though Linux Distributions may already have dropped support long ago.

Debian dropped support for i586 in 2016 with its Version 9.

The FDIV Bug on Windows 7 with the well known 4195835/3145727 operation. The built-in calculator is not affected and returns the correct result, while the calculation on PowerShell used the FPU and is incorrect. An affected Socket 5 100 MHz SX960 was used - CPU-Z Validation.

Aero can work on Pentium MMX, here with a GeForce 6200. A Tillamook 267 SL2Z4 running at 385 MHz was used - CPU-Z Validation.

The experiments were conducted on a Gigabyte GA-5AX. The AGP Aperture Size should be reduced to 16 MB to avoid Windows running for some reason in 16 colors mode and failing to load the graphics drivers.

Aero on Pentium MMX! — The FDIV Bug on Windows 7 with the well known 4195835/3145727 operation. The built-in calculator is not affected and returns the correct result, while the calculation on PowerShell used the FPU and is incorrect. An affected Socket 5 100 MHz SX960 was used - CPU-Z Validation.

Aero can work on Pentium MMX, here with a GeForce 6200. A Tillamook 267 SL2Z4 running at 385 MHz was used - CPU-Z Validation.

The experiments were conducted on a Gigabyte GA-5AX. The AGP Aperture Size should be reduced to 16 MB to avoid Windows running for some reason in 16 colors mode and failing to load the graphics drivers.

Trivia

The computer in which the FDIV Bug was discovered was going to be trashed at some point in early 2000, but someone retrieved it before it happened and posted about it in 2011. We are curious to know where the machine is nowadays...
Thomas Nicely was studying problems related to Prime Constellations when he found the Bug. Riecoin, a project that Stelo.xyz supports, also uses them for its PoW.