The modification was to help avoid a duodisk erasing a diskette under some circumstances. Either of these links has all the info, look under section 6 & 7. I do not recall having a boot issue on my Rom3 though. (Of course I normally do not have my 5.25s even hooked up.) http://home.swbell.net/rubywand/Csa2FDRIVE.html#006 http://www.faqs.org/faqs/apple2/faq/part9/ Thankx, Ed