Intel has decided against releasing some promised updates for older chips to mitigate against the Spectre vulnerabilities.
The company has been releasing microcode updates for the flaws at staggered intervals over the past month.
Its Skylake, Kaby Lake, Coffee Lake and Broadwell and Haswell processors received patches in February to address variant 2 - the branch injection vulnerability - of the Spectre chip flaw revealed earlier this year.
Fixes for Sandy Bridge and Ivy Bridge were released last month.
However in updated guidance on its microcode plans [pdf], Intel revealed it had decided it would no longer provide fixes for a number of older processors.
The affected chips were released between 2007 and 2009, and include processors with the code names Bloomfield, Clarksfield, Gulftown, Harpertown, Jasper Forest, Penryn, Wolfdale and Yorkfield.
Intel also won't provide microcode updates for two SoFIA Atom processors released in 2015.
The company gave a handful of reasons for deciding not to release microcode updates for the nine chip families: architecture that prevents a "practical implementation" of a Spectre fix, limited commercially available system software support, or because they were most likely implemented as closed systems and therefore less exposed to Spectre-based attacks.
Intel last month said it had released microcode for all products launched in the past five years that are vulnerable to the Spectre attacks.