Desktop computers and notebooks with AMD chips accounted for 49.8 percent of PCs sold in domestic stores for the month, compared with Intel's 48.5 percent of the market, according to the Current Analysis report.
"AMD did the unthinkable by surpassing Intel in October. Continuing to hold this lead in the holiday season would be a colossal win for the company," Matt Sargent, Current Analysis research director, said in a statement.
Last month, AMD's slice of the U.S. retail store pie reached 67.7 percent for desktops, up from 52 percent in September. And its share of the notebook market in that category rose to 31.5 percent in October from 26.2 percent in September.
Although AMD's overall share of the U.S. retail store market surpassed Intel based on units sold, it failed to generate more revenue than the industry giant. Intel chips, which have a higher average selling price, accounted for 57.6 percent of the U.S. retail market in October based on revenue, while AMD lagged at 40.1 percent.
Intel also is still the market leader when factoring in overall PC sales in the U.S., including machines purchased through direct sellers. That top position is bolstered by Intel's exclusive relationship with direct seller Dell, a top supplier of PCs.
Nonetheless, the lead in retail space will help advance AMD toward its long-term goal of. AMD currently has approximately 17 percent market share.
Intel's retail slip comes as it copes with other headaches, involving antitrust agencies in foreign countries.
Intel agreed in March to, which called on Intel to halt the practice of requiring PC makers to limit the use of competitors' chips in order to receive monetary rebates.
In June, the Korea Fair Trade Commission requested documents relating to the marketing and rebate programs of an Intel foreign subsidiary. And in July, the European Commissionas part of an antitrust investigation.