i got 8.4 CGPA in 10th, got 78% in 12th and UG score was 8.17 CGPA . Can i get a call from A,B,C IIM if i get a yood score in CAT

Hi
So IIMs tend to be transparent and release the criteria for selection.
But once the scores are out and shortlists are announced there will be disappointed faces in the crowd who themselves have felt that they checked every box yet didn't received the call.
The issue is the process is more complex with a multitude of variables involved and a lot depends on the overall profile of people who have appeared for the exam.
So it is basically a futile effort to ponder about your chances for a shortlist now. This fear of not getting shortlists because of poor academic  performance in the past will haunt you and will make you question whether to proceed further with your preparation or not. But for the time being please try to silence this mental chatter and instead focus on the exam.
P.S - Your acads are decent and a really good percentile will definitely get you a call from any one of the top 3. But if you feel really under confident try to do some really good certification courses like CFA, this will help your profile tremendously

There are 20 IIMs and each has its own selection process.Because CAT exam will be held at different slots, CAT scores will be normalised to ensure equivalence in the difficulty levels of the exams for both slots. IIM Kozikhode will normalise the CAT scores using percentile equivalence. Adjustment of location and scale differences of score distributions across different norms and then scores will be normalised. The 20 IIMS and all the Participating Institutions will announce their Cut offs. The cut off is prepared after checking various factors. MBA aspirants will have to apply separately to all the Colleges that accept CAT scores. While CAT score remains the main criteria for selection, IIMs also consider other factors like previous academic performance, work experience, gender and Academic diversity. CAT exam paper can be Categorised into 3 parts:

Quantitative Ability

Verbal Ability and Reading Comprehension

Data Interpretation and Logical Reasoning

We shall enlist the admission criteria of all the 3 IIMS here:

IIM AHMEDABAD:

QA     DLR      VARC     Overall

General:                               70       70         70           80

NC-OBC/Trans:                    65      65         65           75

SC:                                          60      60       60            70

ST:                                          50       50       50           60

PwD-UR,OBC,SC:                 60       60      60            70

PwD: ST:                               50       50        50           60

At different stages of Selection process, Application rating process is included. The complete list of rating at various levels can be looked at: https://www.iima.ac.in/web/pgp/apply/domestic/admission/selection-process

IIM BANGALORE:

QA   DLR   VARC   Overall

General:           80     80      85         90

NC-OBC:          70     70      75         80

SC:                    65     65      70       75

ST:                    60      60     60        70

PwD:                50       50    50        60

For all the Candidates shortlisted, the 10th and 12th board results are initially adjusted by dividing each such score by 90th percentile score of that board. And then an adjusted score is calculated for the Bachelors degree for each of the candidates based on the final scores obtained by the candidate are used for the Bachelors degree and professional degrees. For example,

CAT = 40

10th board = 20

12th board = 10

Bachelors = 20

Gender Diversity = 2

Work Experience = 8

The 40 points for CAT are derived from the performance in each of the three sections as follows:

Verbal & Reading Comprehension - 14 points

Data Interpretation & Logical Reasoning - 16 points Quantitative Aptitude - 10 points.

IIM CALCUTTA:

QA        DLR       VRC        Over All

OPEN:                75         80         80             85

NC-OBC:           65         65          70            75

EWS:                 65         65          70            75

SC:                    60        60           65            70

ST:                    55         55          55             65

PWD: 55 55 55 65

And the final selection is based on:

CAT 2019 Score 30

Personal Interview 48

Written Ability Test 10

Academic Diversity 04

Work Experience 08

Total 100

Going by all these selection criteria if you score 99% in CAT 2019, you can get a call from these 3 IIMs. And the final selection depemds on your WAT and PI round performances.Your chances at IIM Ahmedabad are more because of their changed policy. Now IIM A has reduced its WAT cut offs to 65% from 70%.