Since you don't know about overclocking it is fair to say that your card is not experiencing the errors as a result of overclocking. Since underclocking still produces the same errors, it means that your extra pipelines have been rendered unusable in some fashion cannot be unlocked, and that the errors are most likely not a result of excess heat. When using softmoded drivers it is important to take into accounts statements like, "The softmod enables the four disabled rendering pipelines in the GPU core of Radeon 9500 Non-Pro/9800 SE cards. Patched drivers for Catalyst 3.10 and later also enable overclocking for all Radeon 9000/9200/9550/9600 based cards." This statement is from the softmodded drivers found on this site. If your card does not meet this criteria than no advantage can be gained. So which card are you using, and where did you get the softmodded drivers?