As per the sthalapuranam vaisampayana was narrating bhagavatham to Janamejayan, and was referring to Lord Krishna's visit to Hasthinapuram as Pandava's Dhoota(Ambassador). Desiring to have the Vishwaroopa darsana they performed Ashwamedhayagam at Kanchi.
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I had been to this temple and was really amazed to see the Moolavar. The moolavar here (krishna's viswa roopam) is in a sitting position is as tall as the Vishnu in a standing posture in the Ulagalanda Perumal koil (my guess wud be around 15 to 17 ft tall). The idol is also very intricately carved to even reflect the body hairs and the nails which looks so natural.
this temple is family owned and not by HR & CE and as such receives very less patronage.