Humans are really slow on information input/output either talking or reading, averaging at about 4 words per second (20bps), comparing to say an average computer network at 1Gbps (50M times slower).
There were lots of miracles at Mt Sinai pertaining to the process of receiving the 10 commandments, as all commandments told in one breath, people seeing the voices and more. However, the recitation of the 10 commandments was done in the old style - G-d reading them out-loud.
I would expect one simple miracle - passing more information in the same amount of time. Probably the whole Torah (300Kb) or all of the Talmud (pp17-18) (around 2M words). As we still don't know what "the whole Torah" means, we can't estimate what Moses studied in the 40 days at the summit, but probably hi did use some "speedreading" technique.
Why didn't G-d use such a simple a miracle - speeding up the process of Matan Torah to allow all the participants to receive the "full course" of the Torah at the same occasion?