* Nikkei rises 0.7 pct, Topix up 0.4 pct * SoftBank, Toshiba, Sharp jump By Tomo Uetake TOKYO, July 18 (Reuters) - Japan's Nikkei share average rose to an eight-week high on Thursday morning after Federal Reserve Chairman Ben Bernanke said the timing of when the U.S. central bank would begin winding down its stimulus was flexible. In mid-morning trade, the benchmark Nikkei rose 0.7 percent to 14,712.12, a level not seen since May 24, while the broader Topix added 0.4 percent to 1,218.46. Bernanke's comments helped Wall Street make modest gains and slightly weakened the yen. The Japanese currency was last quoted at 99.76 yen to the dollar on the EBS platform after coming close to 99.00 on Wednesday. "Neither U.S. stocks nor currency markets reacted to Bernanke's testimony significantly, which is supporting the Tokyo market today," said Mitsushige Akino, chief fund manager at Ichiyoshi Asset Management. "There are many investors who want to sell stocks. But with the Upper House election looming this weekend, they will wait and see, betting on the possibility of a post-election rally." Akino expects that the Nikkei will struggle to post big gains this week. Index heavyweight SoftBank Corp jumped 6.3 percent after Alibaba Group, a Chinese e-commerce giant in which it has a stake of about 30 percent, nearly tripled its net income in the first three months of the year. A fund manager based in Tokyo said short-covering was supporting the gains. SoftBank's stock price slumped after Standard & Poor's cut its debt rating two notches to "junk" earlier this month. It was the most-traded stock on the main board by turnover. Other notable gainers included Toshiba Corp, which rose 2.9 percent after the Nikkei business daily said Toshiba and Elpida Memory Inc plan to invest in capacity expansion as demand for smartphone chips rises rapidly. Sharp Corp advanced 2.5 percent after the Asahi Shimbun newspaper said the company is expected to post a smaller operating loss than initially expected for the April-June quarter, helped by rising sales of solar cells and a weaker yen. The benchmark Nikkei has fallen 7.7 percent from this year's peak of 15,942.60, but is still up 41.5 percent this year.