[comp.dcom.modems] Odd modem problem on 8MHz PC-clone

Mitchell_K_Hobish@cup.portal.com (03/01/88)

A caller to my BBS has tried to use her Everex 1200 modem on an 8MHz
IBM PC compatible, using a NEC V-20 CPU.  THe system appears to work
just fine at the standard 4.77MHz, but when she kicks into the 8MHz
turbo mode, all she gets is garbage on the screen.  According to her,
it looks a lot like line noise.  Cutting back to 4.77MHz during the
same connection reestablishes clear contact.  Can anyone help us
figure out what's going on here?

Thanks in advance.