Nvidia gains 20% weighting and attracts billions in investor demand, while Apple experiences a decline in major tech fund.

The chip giant will be forced to acquire more than $10 billion worth of shares by a major tech fund due to its blistering rally.

The index that follows will soon rebalance, based on an adjusted market cap value from Friday's close. According to Matthew Bartolini, head of SPDR Americas Research, the new calculations show Nvidia as the top stock in the index, followed by Apple.

If there were no caps on the index, all three stocks would have a weight above 20%. However, diversification rules limit the cumulative weight of stocks with at least a 5% share of the fund. As a result, Microsoft and Nvidia will likely have a weight of around 21%, while Apple will be down to about 4.5%, Bartolini said.

The index rules that previously kept Nvidia's weight artificially low have been changed, and as of June 14, Microsoft and Apple both held about 22% in the fund, while Nvidia held 6%.

The race to finish in the top two was decided on the final day. According to FactSet's market cap data as of Monday, all three companies have a market cap of over $3.2 trillion and are within $50 million of each other. However, this data differs slightly from the calculations used in the index.

The XLK fund has over $71 billion in assets under management, so a 15% change in the fund would result in more than $10 billion. SPDR does not disclose specific trading strategies related to rebalancing.

The Technology Select Sector Index from S&P Dow Jones Indices is used to determine the market cap of the fund, which follows this index. The rebalance will officially occur at the end of this week.