Re: Plus/4 RS232 woes

      From: Gerrit Heitsch <gerrit@laosinh.s.bawue.de>
 To: cbm-hackers@musoftware.de 
 Sent: Thursday, September 6, 2018 2:29 PM
 Subject: Re: Plus/4 RS232 woes
   
They had something like this in the PC... I have seen ISA cards that 
didn't have a crystal and one of the UARTs was a special one (Winbond 
86C451, you can find the datasheet online). It used the 14.318 MHz from 
the mainboard to generate the baud clock for itself and a possible 
second UART on the same card.

The later MSX machines had a single clock ~21 MHz that fed to the Video Chip. The video chip would divide this down and output an NTSC clock signal to feed to the video encoder AND also the sound chip. Not sure how they handled serial...
Steve