There is &quot;antifuse&quot;, although it&#x27;s a little slow to program. Commonly available on chips in small amounts for secure key storage, serial numbers, calibration etc.<p>I&#x27;m not aware of anyone selling standalone parts, but here is an IEEE paper: <a href="http:&#x2F;&#x2F;ieeexplore.ieee.org&#x2F;xpl&#x2F;login.jsp?tp=&amp;arnumber=1240972&amp;url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4%2F27824%2F01240972.pdf%3Farnumber%3D1240972" rel="nofollow">http:&#x2F;&#x2F;ieeexplore.ieee.org&#x2F;xpl&#x2F;login.jsp?tp=&amp;arnumber=124097...</a> (512Mb in 2003!)<p>If Google really wanted to, they could make a couple of petabytes of slow-to-write memory by commissioning it themselves for low numbers of millions of dollars. But I suspect they value the rewritability.<p>See also <a href="http:&#x2F;&#x2F;www.eetimes.com&#x2F;document.asp?doc_id=1328234" rel="nofollow">http:&#x2F;&#x2F;www.eetimes.com&#x2F;document.asp?doc_id=1328234</a>