Work upgrading every telephone exchange in Wales for superfast broadband will begin by September 2015.
Dozens more towns and villages are due to be connected by 2016, as many firms say they are still missing out.
The Welsh government says it is on target to see fast internet available for 96% of premises under its £425m Superfast Cymru venture with BT.
In June 2014 superfast broadband was available in 58% of premises in Wales, compared to 78% across the UK.
Deputy Minister for Skills and Technology Julie James said: "By the time the Superfast Cymru programme is completed in spring 2016, Wales will be one of the most highly connected countries in Europe."
Ann Beynon, BT Director for Wales, said: "This is big news for Wales as people will now know when work will start for every single telephone exchange in Wales.
"It's probably the biggest engineering programme Wales has seen in the last ten years with the potential to improve the lives of individuals, families and businesses across Wales."
Just under half of the spend - £205m - is coming from the Welsh and UK governments and European funds, with BT providing the rest.
Superfast Cymru is listing exactly where and when exchange work will take place. However, homes and businesses will still need to sign up with an internet service provider once the optical fibre network has reached their neighbourhood.
Communications regulator Ofcom reported in August that while Wales was catching up in the rollout of superfast broadband, the number of people signing up for it still lagged behind the rest of the UK.
Meanwhile, the Wales Audit Office is reviewing whether the project is delivering effective value for money.Back