It’s like this. I keep hearing about how the latest P4 chip has 90 trillion trillion transistors on it or whatever. Now, If I bought one of these chips and used it in my computer for ten years of gaming, would it still have EXACTLY the same number of transistors as it did in the box? Surely some would burn out? And just how necessary are all of the transistors? If one of them happened to fry, would the chip still work as well as it did before , or would it stop working?
The number and purpose of the transistors stays the same.
If one died it could wreck the whole thing or it could not matter at all. It depends. Some stuff on chips is used just for testing the chips. If transistors there died you probably wont notice. On the other hand most of the stuff on the chips needs to be there and working or you will have problems. You could have a problems only with minor exception cases or it could be really dead.
It’s one of the primary motivations for using solid state electronics (e.g… transistors in CPUs) that they don’t ‘burn out’ with use. The LED (common in most traffic signals, and starting to see use in headlights & flashlights) is another example of a semiconductor device that doesn’t ‘burn out’ - the other components like switch contacts will probably wear out before the diodes do.
Not that they can’t be permanently damaged, though with something like a computer chip it’s as likely to be the connections (wires) that are destroyed as the transistors themselves.
I’m probably wrong, but I think the main factors in degradation over their lifetimes are high-energy radiation and diffusion of the materials they’re made of.
Semiconductor devices do “burn out.” Many are non-operational due to process induced defects. An old analogy states:
“If you expand a silicon chip to the size of Manhattan,
one pothole stops all traffic.”
For this reason, Gordon Moore (an Intel founder) invented the concept called “redundant memory.” Semiconductor memory devices have some of the most dense arrays of transistors in any integrated circuit. DRAM memory designs attempt to avoid this through the use of capacitor cell structures. SRAM and RAM memory all rely upon transistor cell designs. In extremely large memory devices, it is literally guaranteed that a few rows or columns of the memory plane will not work.
Redundant memory designs provide spare rows and columns of memory whose addresses can be encoded post-fabrication so as to replace defective regions in the main memory field. While this must be done immediately subsequent to packaging and electrical test it does represent one example of chips losing transistors as they go along.
Another example that addresses your question more directly is the concept known as “wafer scale integration.” Typically, after fabrication a wafer is then sawn into individual chips known as “dice.” These go through package assembly and electrical test before being sold. Computers are built from assorted RAM and PROM memory devices, CPUs (Central Processing Units), ALUs (Arithmetic Logic Units), and other packaged circuits. Wafer scale integration is an entirely different approach to computer fabrication.
A wafer scale computer would consist of an entire intact wafer. The wafer would contain specific groupings of devices. A CPU chip would be bracketed by bulk memory chips on two or three sides and interface connections on another. Scattered across the wafer’s surface would be all of the devices necessary to assemble a complete computer. The assembly process would begin by identifying a functional processor. Using external stimulation, the processor would be instructed to identify adjacent memory chips needed to support it. Once verified as operational, these memory devices would be recruited and electrically connected to the processor using fusible links. Subsequent testing and qualification would permit a functional computer to be constructed by interconnecting numerous separate devices located on the same wafer. Typical designs envisioned the self-structuring process as a serpentine connection path snaking its way across the wafer’s face.
Where this relates to the OP’s initial question is in the principal of self repair. A wafer scale computer would be able to conduct self repair by sensing when a specific device had failed and then locating a suitable nearby replacement candidate. Onboard algorithms would instruct the processor to seek out and link up to a new functional chip while destroying any electrical connections to the old (and now defunct) device. In this way, wafer scale integration seeks to provide computers with “self-healing” technology. Gene Amdahl of Amdahl Computers established Trillium Corporation in an attempt to realize this concept.
Current device fabrication technology does not permit CPUs and RAM devices to be constructed using the exact same sequence of layer thickness and materials. Operating speeds and power dissipation cannot be generalized in such a fashion. The very low yields for wafer scale integration could not possibly compete with extremely cost efficient single device packaging currently on the market. While MCMs (Multi-Component Modules) do approach some of the high density and speeds envisioned for wafer scale integration, such a monolithic design concept awaits more advanced technologies like nanoassembly before they will be realized.