[jerryr]

That sounds very similar to my experience with toy development. For a toy that played a bunch of pre-recorded sounds, we used a 4-bit Winbond MCU (their MCU division is now Nuvoton) that had a tiny bit of RAM and a ton of mask ROM. Firmware development was done in assembly and targeted a huge (physically large) emulator for test/debug. When we were satisfied with the firmware, we'd send it off to our CM, who would then order the parts with our FW in ROM. They'd get back bare die parts, which were wire bonded to the PCB and then epoxied over (that miserable "glop top" packaging, which is the bane of many teardowns). Development was a bit painful, but high volume production was extremely cheap.

Edit: Oops. I conflated projects. The toy project actually used a SunPlus MCU, not a Winbond MCU. It was an 8-bit RISC CPU running at 5MHz with 128 bytes RAM and 256KB mask ROM. The ROM held both the program and audio samples. I don't recall what encoding was used for the audio.

[nickpsecurity]

Well, I'm curious which project used a 4-bitter. Jack Gansle and Robert Cravatta did a survey a while back:

http://www.embeddedinsights.com/channels/2010/12/10/consider...

http://www.ganssle.com/rants/is4bitsdead.htm

The two examples were timepiece designs and Gilette Fusion ProGlide. On top of getting yours, I'm curious if any of these cheap MCU's in the article could today have met whatever your requirements were for a 4-bitter?

[jerryr]

It was also for a low-cost audio application, but it wasn't a toy. This was back in 2001 or so. The MCUs in this article all only have ~1KB ROM, which wouldn't have been enough for our audio samples. We needed >256KB. The "4-bitness" was just incidentally what Winbond offered with a large ROM at the time. However, the SunPlus that we later used in the toy also offered a large ROM with an 8-bit CPU for a similar cost. So, while I can't authoritatively say that 4-bit is dead, it does seem like there are a lot of alternatives in similar price ranges now.