u/Electrical_Door_87

Watched it today. Absolute cinema.

Hello! While gathering ICs for my ACS-M project, I got my hands on one of these - the x89s. But what is it and why you most likely have never heard of that?

In a nutshell - 8089 is an I/O coprocessor which was rolled out as a part of MCS-86 family of chips. It's capable as heck, functioning like a CPU of its own, featuring a 16-bit multiplexed bus, request handling and requiring it's own support chips - the same ones 8086 would use.

What is it capable of? The grand idea behind it was to decrease the load on CPU by allowing the i8089 to manage RAM->I/O relationship, DMA, copy-paste stuff from RAM and back, interact with controllers using its wide bus and be the perfect I/O handler that would work asynchronnous and autonomously.

What went wrong? Well, nothing. It had its use, although not as much as one could expect. While Intel praised it in its datasheets and suggestions for a system design, the 8089 was rarely used, with the most prominent example being the Apricot PC. The problem - IBM chose to utilize i8237 DMA controller, much cheaper and "dumber" alternative, which couldn't do many thing i89 could. The i89 was then forgotten, with latter I/O coprocessors not receiving x89 name (unlike x87 for math coprocessors).

Why would I use it? It's really nice way to make a multiprocessor system, as i89 can function as a master, have advantages over i8237 and provides more benefits towards the increase in free system resources.

So, that's all for now.

Hello, this is a first post about a project that boiled in my head for months, as now it came to something exact. This is ACS-M, Alpha Computer System, the project with the goal to create one of the most powerful 8086-based systems. It's not intended to be IBM-compatible by default, but I'll think about it. Now here is the main prototype "schematics" of the project layout. It'll feature two i8086 CPUs (both in MASTER, with higher priority of solo-86 block), one i8089 (very powerful and usable I/O IC), 8087 and additional subsystems in future. It'll take me some time to start buildng it from the scratch.

So, if you have some questions, or some information that may be useful for it in the future, please share! I want to discuss the possibility of building something like this at all.