What
@FunkDoc1112 said is accurate.There were a few articles/videos/podcasts about the album for the 20th and 25th anniversary, and Hav talked a little bit more about the beats, and said that Tip helped out on a few more than just what was credited in the liner notes.
Semi-related side note: Hell on Earth is the only Mobb album fully produced by Havoc, and that ‘96 - ‘98 era is my favorite era of Hav beats. He said that was the worst time of his personal life and it really came through in how dark the beats were.
And this from 2011:
The Making of Mobb Deep's 'The Infamous'
Track by track breakdown.
Survival of the Fittest:
“Then Tip gets a hold of it. Tip leaves the loop just like it is—the same way that Havoc caught it—but then just infiltrates it entirely on the drum situation. It intensifies the entire record. If you ever hear the original, it’s ill, it’s gloomy, it’s street, but it’s nowhere as huge as Tip made it when he just changed up the drums. He just implemented that over the loop that Hav had and then just added so much on top of it.”
Eye for an Eye:
"He had an entirely different rhyme when it had the Al Green loop on it. I think Tip might have touched it a little bit, but for the most part Hav kinda did a wonderful job on that one in terms of just chopping up the loop [so we didn’t have to clear the sample].”
Up North Trip:
“Q-Tip enhanced the drums on that lovely. If you listen to ‘Up North Trip’ you’ll hear the snare kind of bouncing a little bit. Cracking a little more [than normal]. Tip gave it a real nice crack compared to what it originally was. He just beefed the drums up on that one.
“Tip also worked with me closely on recommending certain engineers that were great for mixes. Hav and P would always do their own drops and Hav would always—and I would always encourage him—be the producer and do the final check on his own shyt.
“The way that Tip contributed to the project was so cool because he wasn’t in there trying to say, ‘Yo, I’m the mixer for this, I’m taking credit for this.’ He was doing great in his career and he had mad love for us.
"He was just in it to help out and make sure it comes out right. Obviously, he got a nice deal. But it was really just trying to see Hav come up and really steer this ship with this group of emcees that he’s got.”
Trife Life:
“That was a record that was done towards the end. Havoc sounded like he was coming into his own [as a producer]. But Q-Tip came in there and mixed it better. I remember us going in and trying to make it a little bit bigger on the drums side and it not really quite coming out the way we wanted it to. Hav scraped it, made it something else, and then Tip embellished it a little bit.”
And actually, reading this over again, Tip helped out with Start of Your Ending, too.
. One of the greatest beats ever!
The way he was able to take light hearted samples like MJ and Jackson 5 and make them sound so demonic and twisted was 
