Technology-wise, no. You are only giving up small efficiency gains in power usage and perhaps calculations per clock cycle. But knowing that it's a 400 MHz ch

Technology-wise, no. You are only giving up small efficiency gains in power usage and perhaps calculations per clock cycle. But knowing that it's a 400 MHz chip you probably weren't expecting the power of a modern desktop. But in terms of actual part numbers, yes. If you throw an old IC on your board because you could get it cheaper than a more modern part, you are risking the manufacturer EOL (end-of-life) that part sooner than you'd want. The manufacturer may have a replacement that is instruction set compatible on the software side and pin compatible on the hardware side, but you are running a very real risk of having to redesign your boards and recode a bunch of software when you can't get that chip any more. But some parts have been around forever and will continue to be around forever. So the designer has to consider for themselves if the old part is popular enough to continue being manufactured. I would have no problem dropping a 555 timer in a circuit, even though it's been around for decades. But I might want to ask the manufacturer about their lifecycle plans for a CPU, considering how fast things change in the industry.