seg@ingres.com (scott e garfinkle) (02/08/91)
In case you were considering the t18pc, think about this. I bought one and discovered after much wasted efort that the (soldered-on) 8250 UART was keeping my throughput at around 70 cps. The only solution was to replace it with another UART (I chose the 16550, of course). Well, after a year, it started developing strange problems with responding to AT commands. Seems possible that a trace was damaged. Telebit wants $290 to repair the board because of the modification (otherwise they get $150, by the way). Also, in case you were wondering, the T18PC is not upgradeable to V.32 capability. -Scott E. Garfinkle Standard Disclaimer
rcd@ico.isc.com (Dick Dunn) (02/09/91)
seg@ingres.com (scott e garfinkle) writes: > In case you were considering the t18pc, think about this. I bought one and > discovered after much wasted efort that the (soldered-on) 8250 UART was > keeping my throughput at around 70 cps. The only solution was to replace > it with another UART (I chose the 16550, of course). Well, after a year, > it started developing strange problems with responding to AT commands. > Seems possible that a trace was damaged... I've been down the first part of this road--unacceptable performance and lost characters with a trailblazer plus PC, so I replaced the UART with a 16550. What a &^%$#!! monstrous pain--I took it very carefully and spent about 45 minutes replacing one chip (with a socket--I did learn a little something along the way!). It works fine now, but it annoys me no end that Telebit makes such fast modems with an obviously-crippled part like the 8250. If they're going to use the 8250 for cost reasons, the least they could do is socket the damnfool thing. Have people tried beating up on Telebit about this? It's not as if it's a new problem! > Also, in case you were wondering, the T18PC is not upgradeable to V.32 > capability. That's another major nuisance. When Telebit was relatively alone, PEP was OK 'cause if you were talking to another machine that had a high-speed modem, there was a good chance it was another Telebit. Supposedly, the design of the Telebit modems allowed them to be upgraded to support newer protocols, yet here we see the most significant need for an upgrade and they can't/won't (which is it, BTW?) provide an upgrade. -- Dick Dunn rcd@ico.isc.com -or- ico!rcd Boulder, CO (303)449-2870 ...Don't lend your hand to raise no flag atop no ship of fools.
wolfgang@wsrcc.com (Wolfgang S. Rupprecht) (02/09/91)
>In case you were considering the t18pc, think about this. I bought one and >discovered after much wasted efort that the (soldered-on) 8250 UART was >keeping my throughput at around 70 cps. The only solution was to replace >it with another UART (I chose the 16550, of course). This brings up a question that has been bugging me about the Telebit PC bus modems: Why didn't Telebit take this opportunity to design the UARTS out of the modem? They could have replaced the two back to back UARTS with a latch pair, or better yet a FIFO pair and made one extremely delay tolerant PC bus modem. Without the serial chips, the modem really wouldn't care *when* you got around to reading the character. The TB's cpu could see that you haven't read the last char and wouldn't stuff another one on top of the first one. If you waited too long the receiving TB would just fill up its internal ram buffer. In PEP mode this could just throttle the sending TB. If the sending modem was also a similar PC bus modem, it would just hold off the next interrupt until it's ram buffer emptied. No bytes need be lost end to end. -wolfgang -- Wolfgang Rupprecht wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang Snail Mail Address: Box 6524, Alexandria, VA 22306-0524