Open Frame PC

Processor: Intel Pentium 90

Manufacturer: from Gateway 2000 P5-90

Year: Varied

Donor: Private, 2025

This exhibit is intended to expose the internals of a computer.  Visible are the microprocessor (under the heat sink and fan), the RAM, the cache memory, the Real Time Clock / NVRAM, the BIOS ROM, chipset, clock oscillator and other parts that make a computer tick.

This PC features a Pentium CPU running at 90 MHz.  Interestingly, this CPU has a silicon erratum (hardware bug).  This "FDIV bug" plagued the first Pentium chips due to an error by the manufacturer.  To see more about this, see the article Pentium Floating-Point FDIV Bug .

All four SIMM slots are filled on this PC, giving it a total of 32MB of RAM.  Since the Pentium has a 64-bit external data bus width and each SIMM supplies only 32-bits, the SIMMs must be installed in pairs.

The Real-Time Clock (RTC) has a small battery internal to the body of the computer that allows it to keep time when the PC itself is powered down.  The chip also uses this battery to maintain a small amount of memory (114 bytes), which the computer uses to remember its own configuration (BIOS settings).  Some machines (particularly earlier ones) have a separate NiCd battery on the motherboard.  These were notorious for leaking and destroying the circuit boards, so it is fortunate that this RTC is a "Dallas chip."