144 0001163368 XXXXXXXX LIVE 0000709283 RS - QUANTUM CORP /DE/ 001-13449 224 AIRPORT PARKWAY SUITE 550 SAN JOSE CA 95110 408-944 4000 PACIFIC INVESTMENT MANAGEMENT CO LLC Shareholder Common Stock Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza New York NY 10004

962127 11728328.13 6526782 04/15/2025 NASDAQ Common Stock 01/03/2025 Cashless exercise of warrants Issuer N 449710 01/03/2025 Cashless exercise of warrants, which were acquired and fully paid for on or before August 13, 2024. Common Stock 04/22/2022 Rights Offering Issuer N 512417 04/22/2022 Cash Y 289,620 of the shares of Common Stock are being sold by OC II FIE V LP ("OC II") and 672,507 shares of Common Stock are being sold by OC III LVS XL LP ("OC III"). Pacific Investment Management Company LLC ("PIMCO") exercises sole voting and investment power over the securities directly held by OC II and OC III and is filing this Form 144 on their behalf. 04/15/2025 /s/ Alyssa Creighton