CMC Magnetics: Announcement from Subsidiary Zhongjia International Investment Co., Ltd. Regarding Disposal of Securities

1. Securities Name: Silicon Integrated Systems common stock 2. Transaction Dates: 114/10/27 (October 27, 2025) ~ 115/4/17 (April 17, 2026) 3. Date of Board Approval: Not applicable 4. Other Approval Dates: Approval level: Chairman's approval April 17, 2026 5. Quantity, Unit Price, and Total Transaction Amount: Transaction quantity (in thousands of shares): 5,818.6 Unit price (NT$): 52.75 Total transaction amount (NT$): 306,933,961 6. Disposal Profit (or Loss) (Not applicable for acquisition of securities): Disposal profit: NT$3,326,251 7. Relationship with the Transacted Company: None 8. As of now, the accumulated quantity, amount, shareholding ratio, and restricted rights (e.g., pledge status) of this transaction's securities (including this transaction): Remaining holdings: 355,900 shares, Amount: NT$18,302,019 Shareholding ratio: 0.07%, Restricted rights: None 9. As of now, the ratio of investment in securities (including this transaction) listed in Article 3 of the "Regulations Governing the Acquisition and Disposal of Assets by Public Companies" to the company's latest financial report's total assets and equity attributable to owners of the parent, and the amount of working capital in the latest financial report: Ratio to total assets: 13.78% Ratio to equity attributable to owners of the parent: 19.30% Working capital amount: NT$8,285,327 thousand 10. Specific Purpose of Acquisition or Disposal: Investment portfolio adjustment 11. Opinions of Dissenting Directors in this Transaction: None 12. This transaction is a related party transaction: No 13. Counterparty and its relationship with the company: Not applicable 14. Date of Supervisory Committee Approval or Audit Committee Consent: Not applicable 15. Date of previous material information announcement for the same event: Not applicable 16. Other Matters to be Specified: On March 31, 2026, authorized traders were given permission to conduct securities transactions in the centralized trading market during the second quarter of 2026.