The Red Dead Redemption PS4 port has been analyzed, and the results show very minimal upgrades on PS4 and PS5.
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Red Dead Redemption v1.03 + PS5 Backport by CyB1K, 60FPS, PS4 9.00 or Lower, PS5 4.03
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Red Dead Redemption PS4 Port Limited to 30 FPS on PS4 & PS5, Has Limited Visual Upgrades - PlayStation LifeStyle
Red Dead Redemption looks extra sharp on PS5 but runs like PS3 version
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