Looking for a DSP chip capable of delivering over 100MIPS equivalent computing power but consumes less than 1mA current...are there any likely candidtes

Hard to say without more information, but I'll guess you probably won't find one.

1mA @ 1.3V (for example) is only 1.3mW! Again for example, TI's C5000 series 16-bit DSP's vary between 0.15mW/mHz and 0.54mW/mHz. If you run one at 100 mHz you can expect somewhere around 15mW to 54mW consumption. Yet again for example, 54mW @ 1.3V = 41.5mA ... Far, far over your stated maximum.  (I used 1.3V because that's the required core voltage for the C5000's @ 100 mHz)

Going about it another way, a 180mHz Cortex M4 (NXP) with DSP and NEON floating point support runs around 80mA @ 3.3V running full-tilt. Not much use to you there either, sorry.

Apollo 2 from Ambiq micro claims current drain of about 10 micro A/ MHz but it’s not clear if this is just when reading from memory or going full tilt...max clock speed is 48MHz so still a bit short

Is the DSP going to be running all time or can it be sleeping for peroids ?

Thanks for the response. It will be running continuously most the time

I believe the closest you will come is something from the Ezairo series from ON Semi.  http://www.onsemi.com/PowerSolutions/content.do?id... The question for their apps people will be the max voltage it will run at, in order to get the speed up.  It has multiple cores and processing accelerators on it to get your MIPs up.

Thanks. This looks like a good option.