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 back side of this card.

All four SIMM slots are filled on this PC, giving it a total of 32MB of RAM.  Since the Pentium is a 64-bit processor (64-bit data bus width) and each SIMM supplies only 32-bits, they 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."