CMC Magnetics (TPE:2323) disposed of 499,000 shares of Asustek Computer (TPE:2357) for a total of NT$318.8 million, according to a Taiwan Exchange filing on Monday.
Each company's shares dropped about 3% recently on Tuesday.
The shares were sold at an average price of NT$638.88 each, between July 16 and July 21.
The sale, which resulted in a loss of NT$8.7 million, was conducted for portfolio management purposes, it said.