Windows NT 3.1 and its mate NT Advanced Server have been quietly certified Posix-compliant after government experts took an unexplained eight months to complete a review that normally takes no more than three. No problems were found with NT’s Posix subsystem and Microsoft Corp insiders were at a loss to explain what caused the delay. Only NT on Intel Corp and MIPS Technologies Inc systems have been certified so far, but Microsoft thinks that the Digital Equipment Corp Alpha certification it also applied for is being held up only by paperwork. Microsoft did not trumpet its success, offering an uncharacteristic and time-sensitive rationale – it claimed that it didn’t want to irritate companies where NT plays second fiddle to Unix by making it appear that a new Microsoft-led push was under way to displace Unix in federal contract bids. In fact NT has already been bid on those Posix contracts based on an opinion letter Microsoft got last August saying that it would eventually be certified. The importance of these government contracts was underscored last week when Microsoft said it has already won some $500m in government business with Windows NT-based bids.