BEIJING/SINGAPORE, April 23 (Reuters) - Chinese universities and research institutes recently obtained high-end Nvidia (NVDA.O), opens new tab artificial intelligence chips through resellers, despite the U.S. widening a ban last year on the sale of such technology to China.A Reuters review of hundreds of tender documents shows 10 Chinese entities acquired advanced Nvidia chips embedded in server products made by Super Micro Computer Inc. (SMCI.O), opens new tab, Dell Technologies Inc. (DELL.N), ...