When I split my workouts, I try to classify the exercises so that I don't over-do any one thing in the same session. For instance, doing both overhead and bench press is an enormous amount of pressing work and should probably be separated.
- Strength, gymnastics, power, endurance, whatever. These don't apply since you're doing essentially all strength movements.
- Pushes versus pulls. (Squats can be considered a type of "push" or their own third category).
- Without getting into bodybuilding-style specificity, upper versus lower body work can be divided.
- Planes of motion, such as horizontal pushes (bench, push-ups), overhead pushes (overhead press, handstands), downward pushes (dips), or multi-plane pushes (like Hindu push-ups).
- Primary and supplementary exercises. Heavy, low-rep exercises that use large amounts of muscle are different than unweighted, higher-rep exercises that may use smaller muscles. For instance, high-rep unweighted dips are more supplementary than heavy triples of overhead press.
Ways to Separate Similar Exercises
With your split, I see problems with the Pendlay rows and the pull-ups being together, as well as the two presses I mentioned before. Since you have chin-ups, pull-ups and Pendlay rows, I'd say you need to either lose one of the exercises, add a C workout, or alternate within the A or B workout, like this:
B: Pendlay rows
If you start overworking a movement type, doing volume work instead of heavy regular sets can also be helpful. For instance, many intermediate weekly templates recommend a 70% or 80% squat day in the middle of two heavy squat days. This allows you to still work the movement and drive adaptation without hosing your recovery.
I'd also split the two biggest exercises, the squats and deadlifts. I would organize your exercises like so, using standard nomenclature that leaves out any warm-up sets (which could be more than 2):
- barbell squats 3x5
- dumbbell over-head press 3×5
- chin-ups, 3 sets to max (adding weight if necessary)
- dips, 3 sets to max
- barbell deadlifts 1×5
- dumbbell bench 3x5
- pull-ups, 3 sets to max (adding weight if necessary)
- weighted sit-ups (machine)
This schedule separates the two big heavy lower-body-dominant exercises (squats and deadlifts) as well as the two dumbbell presses. You're still doing two pressing movements (dips and overhead press) on the same day, which is not ideal but should be fine. (Dips could be considered accessory work in contrast to the heavy overhead presses.) In this schedule, you're doing one Big Heavy exercise, one Heavy Press, one Upper-Body Pull, and one Supplemental exercise (dips and sit-ups). Note that I dropped the Pendlay rows, since you're already doing pull-ups out the wazoo.
Practical Programming by Rippetoe and Kilgore has an intermediate split program, and discusses the relevant principles in detail. I'd buy a copy if I were you.