Intel’s play for the legacy chip market was almost an oddity. Most of the recent high-profile U.S. chip-related efforts–the CHIPS and Science Act, export restrictions on China, and onshoring manufacturing–largely focused on advanced chips. However, most chips manufactured today are not advanced chips, but legacy chips. Two-thirds of the chips sold today are manufactured using technologies that were commercialized before 2005. Almost a quarter of the chips sold today are manufactured using technologies from the last century! In fact, a majority of the ~500 chip manufacturing plants operating today worldwide were built in the last century.

Legacy chips are at least as critical as advanced chips both in terms of economic importance and national security. Some 95% of the chips used in the automotive industry are legacy chips. Several other critical industries–medical devices, consumer electronics, infrastructure, industrial automation, and defense–also rely heavily on legacy chips. Russian military equipment found in Ukraine famously had legacy chips yanked from refrigerators and dishwashers.

In fact, the COVID-era chip shortage was primarily a shortage of legacy chips, not advanced chips. One’s iPhone 13 Max got delayed not because of its advanced workhorse chips–but due to the unavailability of a large number of legacy chips that the device requires for its operation.

The main reason lawmakers and the industry have largely overlooked legacy chips is that profits mostly come from the expensive advanced chips, whereas commoditized legacy chips often sell for pennies. The average cost of a chip sold today is less than 50 cents. In fact, chips built using pre-2005 technologies make up two-thirds of sales but only a tenth of the overall chip industry’s revenue.

But there is no room for complacency. The gap between the demand and supply of legacy chips has been increasing unsustainably. Consider the automobile industry. The global automotive semiconductor market is expected to grow by over 11% per year for the next few years. However, the projected annual growth in manufacturing of legacy chips is only 2%. It’s simply not economically attractive to invest in legacy chip manufacturing. The cost and spin-up time for a new fab for legacy chips are far too high considering the wafer-thin profit margins. Most legacy chip fabs exist today only because they once produced then-advanced chips–it was the profits made from selling those advanced chips that paid for the cost of setting up those facilities. The lack of new investment despite fast-increasing demand (only one-sixth of the semiconductor investment goes toward manufacturing legacy chips) may blow up into a severe chip shortage unless something changes.

Complacency around legacy chips is also dangerous because it may soon compromise America’s security and strategic autonomy.

Today, almost three-quarters of the manufacturing capacity for legacy chips is based in Taiwan and China, resulting in the same supply chain dependence as for advanced chips. Hypothetically, China could threaten supplies someday and hold the U.S. economy hostage.

China has been investing heavily in the manufacturing of legacy chips, especially in the aftermath of export controls on advanced chips. Some estimates predict that China may build more legacy chip fabs in the next few years than the rest of the world combined. They can eventually box everyone else out, especially through overproduction and loss-leader strategy. It has happened before–the solar industry is a prime example. China can then either turn off the spigot at will–or have immense leverage over everyone else. This dependence on China-based supply chains would be ironic considering that it would be created in part due to the actions taken to reduce dependence on China (for advanced chips).

That creates vulnerabilities for the U.S.–and undermines trust in the chip supply chain, especially in the defense and critical infrastructure sectors. The loss of the legacy chip market can potentially also lead to the loss of downstream critical markets such as electric mobility.

Government subsidies may help convince the U.S. semiconductor industry to build more legacy chips–but there may not be much appetite for more chip subsidies after the CHIPS Act. Friendshoring may be more effective, especially in low-cost allied countries such as India. Export controls on tools and technologies required for producing legacy chips that include volume or cost-based restrictions on production may help prevent overproduction. Import controls and tariffs can be used to prevent dumping. Innovation in legacy chips may help U.S. chipmakers survive a price war. Many applications of legacy chips require safety qualifications. U.S. control over standards bodies may help prevent China’s domination of downstream industries–and insisting on open security standards may help retain some trust in the supply chains.

Considering the enormous amount of attention and resources the U.S. chip industry has received recently, the feeling that chip-related problems have been addressed can be understandable–but an unaddressed danger is lurking within the supply chain of legacy chips. These chips deserve the same level of attention as cutting-edge semiconductors.

Rakesh Kumar is a professor in the Electrical and Computer Engineering department at the University of Illinois and the author of Reluctant Technophiles: India’s Complicated Relationship with Technology.

The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune.

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