This is turning out to be the year of the upgrade for many computer gamers, thanks to the arrival of blockbuster game titles such as Doom 3 and Half-Life 2, on its way to retail shelves after a year's worth of delays.

Doom 3, released this month, has ushered in a new level of realism for computer gaming graphics, incorporating elaborate, quick-moving monsters, ominous shadows, and clouds of smoke and red fog designed to immerse gamers in a shoot-'em-up fest.

But gamers playing with yesteryear's computer might not be able to see all the fine details its creators worked in, because smoke and light effects consume a lot of computing power. Play the $55 Doom 3 on a cheap-o computer and you'll either have to do without its best graphic effects or watch the game turn into a jerky slide show whenever a gaggle of fireball-throwing demons shows up.

It has been years since a new game caused systems to creak and strain so much; Id Software Inc., the company behind Doom, has a long history of nudging gamers into either upgrading or buying new systems altogether.

"We don't mind pushing people a little bit to upgrade," Todd Hollenshead, Id's chief executive, wrote in an e-mail. "If you've got the content or the 'killer app,' then you're in the best position to push the envelope."

Makers of high-end machines catering to hard-core gamers say sales increased between 10 and 20 percent in the days before and after Doom 3's release.

"It's just been awesome," said Rahul Sood, founder and president of Voodoo PC, a small computer company based in Canada.

Though the average price for a new PC has dipped below $1,000, the system Miami-based computer maker Alienware Corp. suggests for Doom 3 players starts at $2,997.

Some gamers who don't want to spend that kind of money instead splurge for a new graphics card, the component that converts computer-generated images into pictures to be displayed on a monitor. High-end cards from companies such as the Canadian ATI Technologies Inc. can process more than 8 billion picture elements a second as they attempt to make the lighting effects in games like Doom 3 look as real as possible -- the best cards cost around $500. Rival Nvidia Corp. has an ongoing special offer in which buyers of its advanced graphics cards can get a free copy of Doom 3 with their purchase.

"No one needs to buy a new graphics card if there's no content to run with them," said Andy Thompson, director of advanced technology marketing at ATI.

New card sales helped boost net income at ATI to $48.6 million in the quarter ended May 31, up from $15 million in the same quarter a year before; the company also cited sales for its technology in cell phones, the Nintendo GameCube and digital televisions.

David Kushner, author of a book about the Doom series, joked that there should be a statue of its lead programmer, John Carmack, "outside every graphics card company on the planet."

Half-Life 2 is also generating demand for high-end computers and equipment. The double dose of hotly anticipated games comes at a time when computer gaming has been in a lull, eclipsed by games designed for play on specialized machines such as Sony Corp.'s PlayStation 2 or Microsoft Corp.'s Xbox. PC games make up about one-fifth of the $6 billion video-game industry, a percentage that analysts say has been slipping in recent years.

But the PlayStation 2, the most popular console, is approaching the fourth anniversary of its U.S. release, and Sony has indicated that it doesn't plan to rush its follow-up to the market. Analysts such as Vince Broady, co-founder of gamer Web site GameSpot, say that pause creates an opportunity for computer game companies to win back players looking for a new thrill.

The number of visits from Web surfers scouring GameSpot for information about Doom 3 on the eve of its release broke records for the site, he said.

"Doom 3 has reinvigorated the PC games market," Broady said. "You haven't seen the same rabid enthusiasm for a game on PC in a long time."

Even for computer gamers who don't care about Half-Life 2 or Doom 3, the releases are significant because the core software, the "engine" that helps create the games' environment, will probably be licensed by other game developers for years to come. Already, the upcoming sequel to a massively popular online game called CounterStrike is to be based on the Half-Life 2 engine.

"The fact is that the technology is the driving reason for interest in the game; the game is almost secondary," Broady said.

Hollenshead said that at Id, his company's rule of thumb is that new games should work on a two-year-old, top-of-the-line system. To run at its lowest graphics settings, Doom 3 requires a processor running at least 1.5 megahertz and 384 megabytes of memory.

But even a system with twice as many resources may still show some strain in rendering the complex, explosion-filled carnage. At gamer site Gaming Forums, a discussion board devoted to what kind of system best plays Doom 3 runs about 60 pages -- a seemingly endless discussion over the finer points of various graphics cards, processors and monitors.

"The software is going to push technology for some time," said Paul Morgan, product manager for Hewlett-Packard Co.'s gaming PC, the Compaq X.

Though gamers represent only a small niche of total processor purchases from Advanced Micro Devices Inc., they are an important enough customer class for the company to devote an entire marketing team to them. The company is a regular co-sponsor of tournaments where the most dedicated gamers come to face off in weekend-long game sessions. Linda Kohout, a marketing manager who focuses on games, estimates that a typical hard-core gamer influences as many as eight other computer purchases a year.

Perhaps the marketing works: AMD and ATI both recently won business from Ben Kuchera, who manages a game store in Kentucky and is the resident game reviewer at tech site Ars Technica.

"People were holding their breath waiting to upgrade," said Kuchera, who used the release of Doom 3 and Half-Life 2 as an excuse to build a new computer system from scratch.

Kuchera's review, like most, gave the game a thumbs up. "Doom 3 made me glad I upgraded," he wrote, "and it made me proud to be a PC gamer."

The monsters and other graphics of Doom 3, released this month, have led some gamers to upgrade or buy new systems, a trend welcomed by computer firms.