> Based on some emails from Andrew I started poking around into the > epia-m serial port problem. Here are my observations: > The 9 pin internal serial port is part of the VT1211 chip, not > the VT8235, or other chips with serial ports. > > Under linux all baud rates are 1/2 what they should be. So if I pick > 115200, I get 57600. If I pick 19200, I get 9600, etc. > > I can fix linux with > setserial /dev/ttyS0 baud_base 57600 > Then the actual baud rate matches what I expect. 38400 and 115200 cannot be > achieved though. > > Andrew says if he boots with Award and the warm boots into linuxbios, the > serial port is 115200.
confirmed (epia-m @ 600mhz). if i power off / on the epia-m then i get the lower speed. > On the epia-m motherboard near the VT1211 chip is a crystal oscillator labeled > KTS24.5X1K, which suggests it is 24.5 mhz. The VT1211 spec calls for a 48 mhz > clock. Don't know if this is the cause of the problem, VT1211 being driven by > 1/2 speed clock. > > My guess is there is some register in the VT1211 that has to be tweaked to > specify the serial port clock divisor. linuxbios doesn't touch this at all. > award bios sets it to match the 24.5 mhz crystal. On cold startup the vt1211 > defaults to assuming 48 mhz input clock. This explains all observations, but > doesn't solve the problem... > > I just put a scope on pin 17 of the vt1211, it appears to be 48 mhz though so > that blows that theory. niki _______________________________________________ Linuxbios mailing list [EMAIL PROTECTED] http://www.clustermatic.org/mailman/listinfo/linuxbios
