For a while, it seemed as if US chip giant Nvidia (NASDAQ: NVDA) was dominating much investor discussion. But lately, Nvidia stock has not received quite the level of attention it was previously.

But it is up 28% in less than a month and is now close to its all-time high. It is also the world’s most valuable listed company, by market capitalisation.

What is going on – and might now be the time to buy some Nvidia stock for my portfolio, in the hope that the latest surge is only the start of a long-term price increase?

Massive value creation without earnings news

That 28% gain means that Nvidia has added over $1trn (yes trillion, not billion or million!) of market capitalisation in under a month.

But here is the thing – it has not issued any financial results during the past month that could help explain such a booming stock price.

There has been other news, however, that could potentially impact the long-term financial performance of the business.

For example, over the past few weeks, Nvidia has announced a strategic partnership with Marvell Technology, and launched Ising, a daftly named family of open source quantum AI models. Such initiatives could help the company increase its revenues over time: the Ising on the cake?

Still, Nvidia stock was hardly cheap a month ago – and I do not think recent product and service announcements can merit another trillion dollars plus of market cap. The tech giant now sells for 43 times earnings.

Watching history in the making

In fairness, Nvidia is an unusual company.

Very few firms see their stock price grow 1,291% in five years. Nvidia has.

Seeing the already valuable business surge so dramatically, becoming the most valuable listed company in history, we are witnessing stock market history.

But could it be that that momentum – and ongoing US market bullishness despite mounting geopolitical and economic uncertainty – help explain Nvidia stock’s recent surge more than business fundamentals?

I’d love to invest – but not now

It may be.

Indeed, Nvidia is not the only US chip firm that has been riding high lately: Intel stock yesterday (27 April) hit an all-time high, having more than quadrupled over the past year.

On the other hand, as companies continue to spend lavishly scaling up their AI capabilities, Nvidia looks set to keep growing.

Consider its most recently quarterly performance as an example. Revenue was an all-time record, growing 68% compared to the same quarter a year before. It was already $39bn then (also a record at that point).

Growing revenue 68% is typically an impressive feat – but especially when the baseline is already so high.

With AI demand holding up for now, Nvidia’s proprietary technology and large installed client base could help it keep increasing revenues and earnings. If that happens, Nvidia stock could grow even from here.

But the current valuation leaves little room for underpeformance by the business. Economic weakness could force firms to cut back on their current high levels of AI spending.

There is also a risk that a rival could dramatically undercut Nvidia on price for a product that offers many of the same benefits.

I prefer more margin of safety. So although I like the Nvidia business, I am not prepared to invest at the current stock price.