i486

2 Articles

A Previously Unknown Supplier For A Classic Chip

June 27, 2024 by 7 Comments

It’s common enough for integrated circuits to be available from a range of different suppliers, either as licensed clones, or as reverse-engineered proprietary silicon. In the case of a generic circuit such as a cheap op-amp it matters little whose logo adorns the plastic, but when the part in question is an application processor it assumes much more importance. In the era of the 486 and Pentium there were a host of well-known manufacturers producing those chips, so it’s a surprise decades later to find that there was another, previously unknown. That’s just what [Doc TB] has done though, finding a 486 microprocessor from Shenzhen State Micro. That’s not a brand we ever saw in our desktop computers back in the 1990s.

Analysis of a couple of these chips, a DX33 and a DX2-66, shows them to have very similar micro-architecture but surprisingly a lower power consumption suggesting a smaller fabrication process. There’s the fascinating possibility that these might have been manufactured to serve an ongoing demand for 486 processors in some as-yet-unknown Chinese industrial application, but before any retrocomputer enthusiasts get their hopes up, the chips can’t be found anywhere from Shenzhen State Micro’s successor company. So for now they’re a fascinating oddity for CPU collectors, but who knows, perhaps more information on these unusual chips will surface.

Meanwhile we’ve looked at the 486’s legacy in detail  before, even finding there could still just be 486-compatible SoCs out there.

It’s A 486 Computer, On A Breadboard

March 18, 2023 by 53 Comments

Ever since the 1970s, a frequent project has been to take a microprocessor and construct a computer system on a breadboard or stripboard. Usually these machines feature a familiar 8-bit processor such as a 6502 or a Z80 because of their breadboard-friendly DIP packages, but there is surprisingly little reason why some of the more recent silicon can’t be treated in the same way. [FoxTech] is leading the way on this, by making a breadboard computer using an 80486DX.

A 1990-era 32-bit desktop CPU seems unpromising territory for this application, but its architecture is surprisingly accessible. It needs a breakout board to gain access to its various lines, but beyond that it can be interfaced to in a very similar way to those earlier chips.

So far there are two videos in the series, which we’ve placed below the break. The first one introduces the project and shows the basic set-up. A 486 running NOPs may produce a pretty light show, but as he starts to show in the second video, it’s capable of more. The eventual aim is to have a simple but fully functional breadboard computer, so he’s starting with logic to decode the 32-bit bus on the 486 into the 8-bit bus he’s going to use.

It’s fascinating to learn about how the 32-bit 486 handles its interfacing and deals with four bytes at once, and we’re very much looking forward to seeing this project play out. The 486 may be on life support here in 2023, but that doesn’t mean it can’t still receive some love.

Continue reading “It’s A 486 Computer, On A Breadboard” →