Bitcoin miners under mixed spotlight as JPM changes ratings

** Shares of bitcoin miners MARA Holdings MARA.O, IREN Ltd IREN.O and Riot Platforms RIOT.O up between ~1% and ~3% in premarket trading

** J.P.Morgan upgrades MARA to "overweight" from "neutral"; raises PT to $22 from $19

** JPM says MARA's approach focused on investing in mining machines rather than owning much of its infrastructure, leading to higher variable costs like electricity and hosting fees

** Downgrades IREN and RIOT to "neutral" from "overweight"; raises IREN PT to $16 from $12, and RIOT to $15 from $14

** Brokerage believes further upside for IREN and Riot will likely depend on either a rise in bitcoin prices or securing high-performance computing (HPC) deals, though the timing of such deals remains uncertain

** "We favor the pure-play operators within our coverage universe, as they offer the best relative value (HPC names feel a little stretched, particularly in light of long and unpredictable sales cycles), and are best positioned to benefit from a rising bitcoin price" — brokerage

** Up to last day's close, MARA, IREN and RIOT were up ~3%, ~80% and ~42% YTD, respectively