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As the PC-clone industry continued to build momentum in the mid- to late-1980s, several problems with the bus began to be apparent. First, because the "AT slot" (as it was known at the time) was not managed by any central standards group, there was nothing to prevent a manufacturer from "pushing" the standard. One of the most common issues was that as PC clones became more common, PC manufacturers began increasing the processor speed to maintain a competitive advantage. Unfortunately, because the ISA bus was originally locked to the processor clock, this meant that some 286 machines had ISA buses that ran at 10, 12, or even 16 MHz. In fact, the first systems to clock the ISA bus at 8 MHz were the turbo [[Intel 8088]] clones that clocked the processors at 8 MHz. This caused many issues with incompatibility, where a true IBM-compatible third-party card (designed for an 8 MHz or 4.77 MHz bus) might not work reliably or at all in a higher-clocked system. Most PC makers eventually decoupled the bus clock from the system clock, but there was still no standards body to "police" the industry.
As companies like [[Dell]] modified the AT bus design,<ref name="lewis19880424">{{cite news | url=https://www.nytimes.com/1988/04/24/business/the-executive-computer-introducing-the-first-ps-2-clones.html | title=Introducing the First PS/2 Clones | work=The New York Times | date=1988-04-24 | access-date=6 January 2015 | author=Lewis, Peter H.}}</ref> the architecture was so well entrenched that no single clone manufacturer had the leverage to create a standardized alternative, and there was no compelling reason for them to cooperate on a new standard. Because of this, when the first [[Intel 80386|386]]-based system (the [[Compaq Deskpro 386]])
Meanwhile, IBM began to worry that it was losing control of the industry it had created. In 1987, IBM released the [[IBM Personal System/2|PS/2]] line of computers, which included the [[Micro Channel architecture|MCA]] bus. MCA included numerous enhancements over the 16-bit AT bus, including [[bus mastering]], [[Burst mode (computing)|burst mode]], software-configurable resources, and 32-bit capabilities. However, in an effort to reassert its dominant role, IBM patented the bus and placed stringent licensing and royalty policies on its use. A few manufacturers did produce licensed MCA machines (most notably, [[NCR Corporation|NCR]]), but overall the industry balked at IBM's restrictions.
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