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The late 1970s and early 1980s saw the rise of both 8-bit home computers and Programmable Logic Devices (PLDs). This convergence led to interesting applications of early PLD technology in 8-bit computer design. This article explores the various subtypes of PLDs that were relevant during the 8-bit computer era, comparing their characteristics and their use in these pioneering machines.

== Simple Programmable Logic Device (SPLD) ==

* GALs were often used in aftermarket upgrades or modifications to existing 8-bit computer designs.

* They allowed hobbyists and small companies to create custom expansions more easily.

== Programmable Logic Array (PLA) ==

* While less common, PLAs were sometimes used in more complex 8-bit computer designs for tasks like instruction decoding.

* Example: The Commodore 64 used a PLA for part of its chip select and memory mapping logic, demonstrating the device's ability to handle complex logic in a single chip.

== Uncommitted Logic Array (ULA) ==

ULAs allowed 8-bit computer manufacturers to create custom chips that integrated multiple functions, reducing chip count and overall system cost. This was crucial in producing affordable home computers.

== Gate Arrays ==

* They allowed for more complex custom chips than ULAs, potentially integrating even more functions into a single device.

* Example: Some later ZX Spectrum models used Gate Arrays instead of ULAs, allowing for cost reduction and integration of additional features.

== Comparison Table ==

| Typical Use || Glue logic, address decoding || Upgrades, modifications || Complex logic functions || Multi-function custom chip || Advanced custom logic

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== Impact on Computer Design ==

Aftermarket Modifications: Devices like GALs enabled enthusiasts to create custom modifications and upgrades for existing 8-bit computers.

== Summary ==