Editing Bus (computing) (section)

===Second generation===
{{Unreferenced section|date=June 2023}}
Second-generation bus systems like [[NuBus]] addressed some of these problems. They typically separated the computer into two [[address space]]s, the CPU and memory on one side, and the various peripheral devices on the other. A ''bus controller'' accepted data from the CPU side to be moved to the peripherals side, thus shifting the communications protocol burden from the CPU itself. This allowed the CPU and memory side to evolve separately from the peripheral bus. Devices on the bus could talk to each other with no CPU intervention. This led to much better performance but also required the cards to be much more complex. These buses also often addressed speed issues by being bigger in terms of the size of the data path, moving from 8-bit [[parallel bus]]es in the first generation, to 16 or 32-bit in the second, as well as adding software setup (later standardized as [[Plug-n-play]]) to supplant or replace the jumpers.

However, these newer systems shared one quality with their earlier cousins, in that everyone on the bus had to talk at the same speed. While the CPU was now isolated and could increase speed, CPUs and memory continued to increase in speed much faster than the buses they talked to. The result was that the bus speeds were now much slower than what a modern system needed, and the machines were left starved for data. A particularly common example of this problem was that [[video card]]s quickly outran even the newer bus systems like [[PCI Local Bus|PCI]], and computers began to include [[Accelerated Graphics Port|AGP]] just to drive the video card. By 2004 AGP was outgrown again by high-end video cards and other peripherals and has been replaced by the new [[PCI Express]] bus.

An increasing number of external devices started employing their own bus systems as well. When disk drives were first introduced, they would be added to the machine with a card plugged into the bus, which is why computers have so many slots on the bus. But through the 1980s and 1990s, new systems like [[SCSI]] and [[Integrated Drive Electronics|IDE]] were introduced to serve this need, leaving most slots in modern systems empty. Today there are likely to be about five different buses in the typical machine, supporting various devices.{{Citation needed|date=October 2020|reason=Experience with contemporary PC architectures seems to focus on unification of different interconnect technologies (ex.: USB-3, DisplayPort, and Thunderbolt ports all carry (or can negotiate to carry) PCIe packets.}}