From: bjjlyates@bellsouth.net   
      
   On 8/10/07 8:53 PM, in article   
   46bd07b6$0$22566$5a62ac22@per-qv1-newsreader-01.iinet.net.au, "Mark   
   McDougall"  wrote:   
      
   > winston19842005 wrote:   
   >   
   >> And why can't you connect at a higher speed? I realize there is a difference   
   >> between connection speed and throughput, but the best of both worlds is   
   >> given when you connect at a high speed (say 38.4kbps) with hardware flow   
   >> control (CTS/RTS). Your throughput will vary depending on what your machine   
   >> might be doing (echoing all text to screen, uploading/downloading, disk   
   >> access), but it will always be running at the fastest speed possible.   
   >   
   > For a start, the UART in the Model 4 won't do higher than 19k200 - a   
   > limitation on the baud rate generator in it.   
   >   
   > And I'm certainly no expert, but I recall reading that (serial?) interrupts   
   > were broken in the Model III, which meant in practice you were limited to   
   > very low baud rates?!?   
      
   Serial interrupts? Are they necessary for communication? Serial interrupts   
   are considered broken on the TI-99 (they use a circular queue in VDP RAM and   
   there is a nasty bug in the interrupt handler). So they generally aren't   
   used.   
   But with hardware handshaking you can have a 38.4kbps connection. Without   
   it, you lose characters when echoing to the screen at 4800. So your   
   throughput _with_ the handshaking when echoing to screen is probably less   
   than 4800, but you don't lose any characters, you lose the throughput   
   instead. And when you aren't echoing the text, it is much faster. Plus, you   
   can stop the remote from transmitting when doing disk I/O, which is great   
   considering the TI-99 doesn't use DMA for disk access.   
      
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