BUZZ-Arm marches on after stellar debut, Needham warns of challenges

** UK chip designer Arm Holdings ARM.O jumps 8.2% to $68.75 in early premarket trading, after soaring ~25% in its debut on Thurs

** Arm closed at $63.59 on Thurs, giving it valuation of $65 bln as it returned to public markets following a seven-year absence

** Needham starts coverage on Arm - whose chip designs power every smartphone in the world - with 'Hold' rating, flags a 'post-smartphone era'

** "Just like Intel finds it difficult to replicate its success outside of PCs... Arm will face challenges outside of smartphones at a time when high-performance computing is replacing smartphones"

** Brokerage says viable alternatives to Arm exist, with Intel and AMD dominating on CPU side, and Nvidia on the GPU side

** Macquarie says Arm's fundamental performance key to future price action; "coming into the listing, tone on revenue growth and earnings sounded lukewarm... any hiccups in the medium term could draw some punishment from the market"

** New Street Research started coverage on ARM with "buy"; TP - $59

(Reporting by Susan Mathew in Bengaluru;)

((susan.mathew@thomsonreuters.com;))