Which US Manned Spacecraft had the First Onboard Computer?

Commander Jim McDivitt and Ed White took the first computer into space aboard Gemini 4 on June 3, 1965. According to James Schefter's book, The Race:

"Their ship was the first to have an onboard computer, a small unit by IBM built into the instrument panel. There had been worries about how it would work in space, even whether it would turn on."

But it did work, for three days in a row, and the IBM executives, emboldened by the success and nervous about press scrutiny, took a full-page ad in the Wall Street Journal to tell the world about their technological triumph.

On the next day the computer refused to fire up. Schefter mentions that:

"John Young was the Capcom that shift, and the IBM brass winced when they heard his suggestion to McDivitt and White: 'Why don't you just kick it?'"