KOSPI and KOSDAQ Rally on VI Triggers and Sector Boosts

The KOSPI climbed 0.78% to 6,307.59 while the KOSDAQ surged 6.27% to 848.89, reflecting a broadly bullish session. Market momentum was driven by volatility‑interruption mechanisms and positive news for optical‑communication, semiconductor and infrastructure stocks.

TAIHAN Fiberoptics Co.,LTD (010170) +18.67%

TAIHAN Fiberoptics surged 18.67% after the market’s Volatility Interruption (VI) mechanism was triggered early in trading, lifting both major indices. The rally was amplified by China’s ban on importing optical‑communication components, which boosted domestic optical‑communication stocks, including Daehan Optical Communications. Despite a reported net sell‑off by foreign investors on August 6, the VI‑driven buying pressure outweighed the sell pressure, propelling the share to its current level. [1][6][4]

Jeju Semiconductor Corp. (080220) +21.49%

Jeju Semiconductor jumped 21.49% as its price recovered to the 80,000‑won mark in the early session, triggering the Volatility Interruption (VI) system that curbed excessive price swings. The VI activation, reported on August 10, indicated strong buying pressure and helped sustain the rally. The sharp rise reflected robust investor appetite, and the broader upward momentum across KOSDAQ stocks kept sentiment buoyant throughout the day. Market participants see the recovery as a confirmation of the semiconductor sector’s resilience. [7][8]

AUK (017900) +14.72%

AUK surged 14.72% as improved market sentiment and tighter supply‑demand dynamics drove buying pressure, pushing the share into the high‑teens intraday. The rally was further fueled by U.S. regulatory moves announced on August 10 to restrict Chinese-made optical transceivers, which heightened expectations for domestic optical‑electronics firms. The buying intensity was sufficient to trigger the VI mechanism twice in the morning, temporarily halting price volatility. These factors combined to lift AUK sharply, despite its modest ROE of 2.5%. [14][13][10]

GS Engineering & Construction Corp (006360) +8.37%

GS Engineering & Construction rose 8.37% after KB Securities issued a bullish report on August 10, setting a target price of 43,000 won and aligning the stock with its current construction‑sector investment strategy. The analyst’s endorsement spurred buying, and the share climbed 8.53% intraday as reported by TopStar News. The positive coverage appears to have resonated with investors seeking exposure to Korean infrastructure projects, supporting the upward move. [16][15]

SANIL ELECTRIC (062040) +15.19%

Sanil Electric jumped 15.19% on strong Q2 fundamentals and growth outlook. The company posted record sales, the highest ever for the quarter, and secured additional data‑center transformer orders, driving investor optimism about AI and data‑center demand. IBK Investment Securities raised its target price to 220,000 won, citing the robust sales and expanding order book. Media reports on August 10 highlighted the “historical‑level sales” and “five‑quarter streak of record results,” while a August 9 note emphasized the upside from the data‑center transformer pipeline. These developments lifted the stock sharply. [17][18][19][20][21][22]

Sources

1. [속보] 대한광통신 VI 발동, 주가 장초반부터 급등...양대지수도 '맑음' — CBC뉴스 · 2026-08-10
2. 대한광통신 주가, 급등세... 왜? — 금강일보 · 2026-08-06
3. 대한광통신 주가, 8월 7일 장중 11,410원 3.07% 상승 — 톱스타뉴스 · 2026-08-07
4. 06일, 외국인 코스닥에서 레인보우로보틱스(+1.14%), 대한광통신(-8.29%) 등 순매도 — 한국경제 · 2026-08-06
5. 대한광통신 투자분석 2026. 08. 06 — 주달 · 2026-08-06
6. 中 부품 수입 금지...대한광통신·빛과전자 등 광통신株↑ — gukjenews.com · 2026-08-10
7. 제주반도체 주가 주초장 급등 8만원선 회복…VI 발동되기도 — CBC뉴스 · 2026-08-10
8. 제주반도체 주가 상승 중 — 아시아뉴스통신 · 2026-08-10
9. 광전자 주가, 8월 7일 장중 7,950원 17.08% 상승 — 톱스타뉴스 · 2026-08-07
10. 광전자 주가 급등흐름…오전 VI 2회 발동되기도 — CBC뉴스 · 2026-08-07
11. 광전자 주가, 8월 10일 장중 9,220원 18.05% 상승 — 톱스타뉴스 · 2026-08-10
12. [서울데이터랩]코스피 거래상위 종목 혼조…혜인 26% 급등, 한화솔루션·광전자 강세 — twig24.com · 2026-08-07
13. 대한광통신·광전자 등 급등…美 중국산 광트랜시버 규제 추진 — 이코노뉴스 · 2026-08-10
14. [특징주] 광전자, 장중 18%대 급등…수급 개선에 투자심리 '활활' : 한국증시 — 재경일보 · 2026-08-10
15. GS건설 주가, 8월 10일 장중 34,350원 8.53% 상승 — 톱스타뉴스 · 2026-08-10
16. [리포트 브리핑]GS건설, '현 시점 건설업종 투자전략의 교집합' 목표가 43,000원 - KB증권 — 뉴스핌 · 2026-08-10
17. [특징주] 산일전기, 역대급 매출에 데이터센터 수주 기대감…10%대 강세 — 에너지경제신문 · 2026-08-10
18. [ET특징주] 산일전기, 2분기 역대 최대매출 · 데이터센터 수주 기대감… 주가 16% 상승 — 전자신문 · 2026-08-10
19. IBK證 산일전기, 데이터센터향 특수변압기 수주 확대…목표주가 22%↑ — 아주경제 · 2026-08-09
20. AI·데이터센터 훈풍 탄 산일전기, 5개 분기 연속 ‘역대 최대 실적’ — v.daum.net · 2026-08-10
21. 산일전기, 16% 급등…2분기 호실적에 투심↑ - 머니투데이 — 머니투데이 · 2026-08-10
22. IBK투자증권 "산일전기, 실적·수주 모두 견조…목표가 22만원으로 상향" — 파이낸셜포스트 · 2026-08-10

This is market commentary, not investment advice.