That would depend on where the populations resided and the relative numbers. If (for example) Toba were the culprit and a large portion of humans lived in Asia while a large portion of the chimps were in Afrika, the effect on humans could have been much greater. It's also possible that there were more chimps around then so killing 90% would still live the chimps with more individuals. There's no reason to expect similar effects on the different species.
Since the world at that period was in the throes of an ice age it can be assumed that few modern humans lived in Europe (unless we can equate Neanderthal as modern).
Asia would have been toast and Africa affected for scores of years due to massive climate upheavals.
It is possible that all that remained were residents of South Western Africa which repopulated Asia during the inter glacial periods ca 60,000ya.
Fits the "Out of Africa" theory.