statement of purpose:

Please describe your aptitude and motivation for graduate study in your area of specialization, including your preparation for this field of study, your academic plans or research interests in your chosen area of study, and your future career goals. Please be specific about why UC Berkeley would be a good intellectual fit for you.

personal history statement: 

Please describe how your personal background and experiences inform your decision to pursue a graduate degree. In this section, you may also include any relevant information on how you have overcome barriers to access higher education, evidence of how you have come to understand the barriers faced by others, evidence of your academic service to advance equitable access to higher education for women, racial minorities, and individuals from other groups that have been historically underrepresented in higher education, evidence of your research focusing on underserved populations or related issues of inequality, or evidence of your leadership among such groups.

The Personal History Statement is required for all applicants. Please note that the Personal History Statement should not duplicate the Statement of Purpose.

This is a little confusing. So if I want to write about when and how I first knew that I wanted to study architecture, should I write it in the statement of purpose or in the personal history statement? 

if it's the motivation of my study, and at the same time it is the background and experiences that that motivated me for graduate study, which on should I write it in? 

Thanks.

Yan