At a time when mobile devices were becoming even more mainstream, lowering power consumption became a key objective. However, as the Android and iPhone market in 2007 shortly revealed, power consumption took a distant third in priority when it came to having a competitive product. Performance remained the number one improvement, allowing an ever increasing amount of desktop-level apps on a smartphone, as the Symbian era came to a close. A couple years ago, in adding to my research collection of processors that were unique or rare, I stumbled upon the ARM996HS.
It is a "clockless" processor in that it is not a synchronous process, but its 100MHz speed may refer to an average speed. Its benefit was offering 1/3rd power consumption of a similar processor, on just 90,000 logic cells. Other processors had been designed to accomplish this, albeit with far more circuitry- the 386SLC, which had around 800,000 transistors (compared to the original 386's 275,000, although comparing a 386 to an ARM was never really a fair comparison), and the AMD LX700, which was also a static 486 Geode processor produce by National Semiconductor (at the time). Edit: The 386SLC was not actually static, the 80386EX was. It is a static processor used in exotic environments like space. The IBM 386SLC did introduce power management features & 8KB of cache, however.) I am curious whether TI has a 486 "license," considering its patent expired more than 17 years ago.
It had appeared in the industry news at the time, but quietly disappeared. Reasons given range from performance to licensing (multiple companies helped develop it), to soft errors/bugs, and economic- smartphones might not have used it, and it wasn't worth the R&D costs if the market was moving towards higher performance chips.
"The ARM996HS current peaks are reduced by a factor 2.5 to 40 percent of the ARM968E-S, the data showed. The ARM996HS has a gate count of 89,000 compared with the 88,000 of the ARM968E-S. Both are based on the ARM9 processor and the ARMv5Te instruction set.
The ARM996HS performance varies between about 50 percent of a 100-MHz clocked ARM968E-S at 1.0 volts and a temperature of 125 degrees centigrade and about 75 percent of the performance at nominal voltage of 1.2 volts and 25 degrees centigrade."
It's also possible it became integrated into smartphones as a co-processor (e.g. Intel Management Engine), but not something the user would have access to.
I was able to find a few presentations that had been distributed at the time.
"Today, hundreds of millions of asynchronous circuits are produced every year,
and many of us may use it on a daily basis without being aware of it. As an example,
asynchronous circuits designed using Handshake Solutions' Timeless Design
Environment (TiDE) may be found in the vast majority of electronic (biometric) passports,
in in-vehicle networks like CAN and LIN, in MEMS-based sensors such as for measuring
tire pressure, in access-control systems, and in Near Field Communication devices such
as Nokia's 6131 NFC phone."
A couple papers were published on it:
Architectural Design Issues in a Clockless 32-Bit Processor Using an Asynchronous HDL
Myeong-Hoon Oh, Young Woo Kim, Sanghoon Kwak, Chi-Hoon Shin, Sung-Nam Kim
First published: 01 June 2013
https://doi.org/10.4218/etrij.13.0112.0598
https://onlinelibrary.wiley.com/doi/epdf/10.4218/etrij.13.0112.0598
Was it a practical processor? Maybe it just hadn't found its niche for the consumer-facing market.
Edit 2: In 2025, a Rochester Institute of Technology student designed a 4-staged asynchronous RISC processor for his Masters Thesis.
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