Why AMD Stock Lit Up Today

What happened

Semiconductor giantAdvanced Micro Devices(NASDAQ:AMD)stock is up a solid 5.7% as of 2:05 p.m. ET Monday -- the first trading day after the Christmas break. Curiously, the reason that AMD stock is up today is the same thing that's been bugging semiconductor investors all year long: the global semiconductor shortage.

So what

By now this story should be familiar to you. All year long, companies that build things that need semiconductors to run them -- which, at this point in history, means everything from PCs to cellphones to cars to kids' toys -- have struggled to get enough semiconductors to manufacture all the products that their customers want to buy.

Evensemiconductor manufacturers are in something of a bind. On the one hand, constrained chip supplies mean semiconductor makers can charge more money for their chips -- but only if they have enough manufacturing capacity to make those chips in the first place. This is why the latest semiconductor news is such good news for AMD stock.

As Reuters reported on Thursday, just ahead of the Christmas break, AMD was able to amend and extend its contract manufacturing agreement withGlobalFoundries(NASDAQ:GFS). Instead of having GlobalFoundries send it just $1.6 billion worth of silicon wafers between 2022 and 2024, AMD will buy $2.1 billion in wafers from 2022 to 2025.

Now what

Of course, this could actually be a "good news, bad news" development for AMD when you think about it. On the one hand, AMD has extended its access to GlobalFoundries', er, foundries for an extra year. On the other hand, though, extending a three-year contract by one year is a 33.3% extension in time, while the number of chips AMD is buying over that longer timespan is just 31.2% more than it was scheduled to acquire over the original three-year timespan.

Net-net, that works out to slightly less access to GlobalFoundries' manufacturing capacity in the fourth year of the contract than in the original three years. And one also has to wonder if, given the rising prices of semiconductors globally, the extra $500 million AMD will be paying for the fourth year, will buy as large a volume of chips as the company was already contracted to acquire in the first three years of the contract -- a fact Reuters didn't elaborate on.

Until we learn more about this deal, the answer to that question will remain up in the air.