I know the Pentium Pro/2/3 chipsets and motherboards all(?) supported it. Unsure of the Pentium 1 as the 430TX on my Tyan Tomcat IV doesn't, and that is a dual processor board. 486 and earlier likely depended on the chipset as there were many.
At work I have two working slot 1 PIII 800's each with 1GB ECC (4x 256MB DIMMS) on a regular Asus board (doing nothing but waiting to go home with me one day). The board reports the RAM is in fact ECC and that it is enabled.
At work I have two working slot 1 PIII 800's each with 1GB ECC (4x 256MB DIMMS) on a regular Asus board (doing nothing but waiting to go home with me one day). The board reports the RAM is in fact ECC and that it is enabled.