On 03/04/11 02:07, Stephen Powell wrote: > On Fri, 01 Apr 2011 06:02:38 -0400 (EDT), MAROUNI Abbass wrote:
<snipped> > I also used to have an IBM PS/2 Model 70. The UART on its motherboard > is a 16550A. According to the manufacturer's specifications, the > 16550A is capable of operating at speeds of up to 256 kbps. Due to the > hardware design of the PC et al, 115 kbps is the maximum bit rate that > can be programmed by software. But by trial and error experimentation, > I found that this UART could be driven at a maximum rate of 38,400 bps. > If I tried to go any faster, I would get garbage or dropped characters. > In this same machine was an expansion board (32-bit microchannel bus) > which contained an extra serial port. It also has a 16550A UART. But I > had no problems driving it at 57,600 bps. Perhaps it would have been > capable of higher speeds than that, but I didn't have a fast enough > device to test it with at the time. > > The point is that all serial ports are not created equal. The most > common PC serial ports use 16550A UARTs, but older and slower UARTs > are used in some older boards. Even if the UARTs are the same, > the actual maximum bit rate can be lower than the manufacturer's > specs, depending on what limitations are imposed by the supporting > circuitry. > <snipped> Ahh the PS/2! The precise scenario I was thinking of when I said "There are/were some problematic serial chipsets" - I couldn't remember off-hand the exact chipset, and was hoping I wouldn't have to dig through old notes to find it. (thanks Stephen) I owned a number of PS/2s - I still regret parting with the 9595 :-/ It was on those machines that I first used home-made three-wire cabling to transfer data. One day I'll have the time to rebuild my PS/2 collection and make use of MCA cards from IBM mainframes - and maybe fix/update the site in the signature. Cheers -- A site about PS/2s http://www.angelfire.com/sc/ottferguson/ It's old, un-maintained, and you'll need to enable javascript - and wait to get past the IBM diagnostics screen :-) Note: the email address is defunct, as are many of the links. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4d97c181.8090...@gmail.com
