Because consoles are closed box affairs they don't get held back by outdated PC standards if they are willing to spend the money and implement their own/different one.
A SSD on the end of a fast bus to the southbridge would be pretty fast and it could replace some of the ram expenses as needed data could be quickly accessed from the drive.
Optical Drive - 150ms seek (PS3) 100ms Xbox360 IIRC.
HDD - 10ms seek (Smaller laptop HDD spin slower than desktop)
Flash - 0.1ms seek.
Ram - xxx Nano seconds lol (something like 120 IIRC???!?!?)
Seek times go 100x slower on HDD vs flash and 10-15x slower on optical than HDD.
This means they could use the SSD as like a level 2 ram for persistant data and store the meaty stuff on the HDD/Optical media and the latency intolerant/frequently accessed data on the ram.
Tease.
