Shares in Irish-based technology company Parthus Technologies fell almost 16 per cent by midday.
The fall came after London broker UBS Warburg reduced its price target on the microchip designer to reflect a "worst case scenario" for earnings, dealers said.
The broker cut its price target to 25p from 45p and repeated a "reduce" stance in a research note distributed to clients over the weekend.
It said semiconductor companies continue to suffer from falling volumes and prices - and in turn therefore continue to assess their R&D budget allocation.
UBS Warburg's note follows Parthus holding an analyst meeting in London and "teach-ins" on its focus technologies including GPS, wireless technologies, power management and application processing. No trading update was given, so the broker made no change to estimates.
Further weight on Parthus came this morning from another broker, Teather & Greenwood (T&G), which commented in its monthly Technolo-Gbulletin that its forecasts for the semiconductor design group "could prove to be optimistic".
In an article highlighting companies with what it sees as stretched valuations, T&G said competition is likely to be tough in Parthus's core markets, which include next-generation mobile handsets and the Bluetooth wireless communications standard.
AFP