Jack Ganssle recently asked me about 4-bit microcontrollers. He noted that there are no obvious 4-bit microcontrollers listed in the Embedded Processing Directory – but that is partly because there are so few of them that I “upgraded” them to the 8-bit listing a few years back. In all the years I have been doing the directory, this is the first time someone has asked about the 4-bitters.
I suspect the timing of Jack’s inquiry is related to his recent article “8 bits is dead” where he points out that the predicted death of 8-bit microcontrollers continues to be false – in fact, he predicts “that the golden age of 8 bits has not yet arisen. As prices head to zero, volumes will soar putting today’s numbers to shame.” I agree with him, the small end of the processing spectrum is loaded with potential and excitement, so much so that I started a series on extreme processing thresholds a few months ago to help define where the current state of the art for processing options is so that it is easier to identify when and how it shifts.
The timing of this inquiry also coincides with Axel Streicher’s article asking “Who said 16-bit is dead?” Axel makes a similar observation about 16-bit processors. I would have liked to have seen him point out that 16-bit architectures is also a sweet spot for DSC (digital signal controllers), especially because Freescale was one of the first companies to adopt the DSC naming. A DSC is a hybrid that combines architectural features of a microcontroller and a digital signal processor in a single execution engine.
A comment on Jack’s article suggested that this topic is the result of someone needing a topic for a deadline, but I beg to differ. There are changes in the processing market that constantly raise the question of whether 8- and 16-bitters will finally become extinct. The big change this year was the introduction of the Cortex-M0 – and this provided the impetus for me to revisit this same topic, albeit from a slightly different perspective, earlier this year when I asked “How low can 32 bits processors go?” I offer that a key advantage that smaller processors have over 32-bit processors is that they reach lower cost and energy thresholds several years before 32-bit processors can get there, so the exciting new stuff will be done on the smaller processors long before they are put on a 32-bit processor.
In contrast, the humble 4-bit gets even less to no attention than the 8- and 16-bitters – but the 4-bit microcontroller is not dead either. Epson just posted a new data sheet for a 4-bit microcontroller a few weeks ago (I am working to get them added to the Embedded Processing Directory now). The Epson 4-bitters are legacy devices that are used in time pieces. EM Microelectronics’ EM6607 is a 4-bit microcontroller; I currently have a call to them to clarify its status and find out what types of applications it is used in.You can still find information about Atmel’s MARC4 which the company manages out of their German offices and is not currently investing any new money into.
So to answer Jack’s question – no, 4-bit processors are not dead yet, and they might not die anytime soon. Are any of you using 4-bit processors in any shape or form? Would you consider using them? What types of processing characteristics define a 4-bitter’s sweet spot? Do you know of any other companies offering 4-bit processors or IP?