nee@cf_su14.Salomon.Com (Robert Nee) (11/20/90)
I have a couple of questions for all the netlanders out there with high speed modems. Thanks in advance. 1 I read in PC Magazine that in order to use a high speed modem at peak efficiency you must have the 16550 UART chip installed in your computer. (not an 8250 or 16450) Fine, but when I looked in my computer the only chip I could find that was even close was a 16452. So my first question is "have I identified my UART?" 2 This 16452 chip is in a socket but it is not of the DIP variety. I don't know what to call it except that it is is a square socket like the ones 80387sx fit into. Do they make 16550s that fit into these square sockets. 3 If the answers to these questions we're yes. Where would you (the experienced high-speed communicator) purchase a replacement high-speed UART. Robert Nee P.S. the computer is a DELL 310 if that helps anyone...
root@zswamp.fidonet.org (Geoffrey Welsh) (11/21/90)
Robert Nee (nee@cf_su14.Salomon.Com ) wrote: >1 I read in PC Magazine that in order to use a high speed > modem at peak efficiency you must have the 16550 UART > chip installed in your computer. (not an 8250 or 16450) The 16550 simply offers a 16-byte FIFO buffer in stead of a transmit hold register and receive data register. This can be importent if (a) you're using an XT which can't process the data quickly enough, and which loses bytes occasionally because of it (the 16550 stores up to 16 bytes, to be fetched whenever the XT gets around to it); this usually happens at 19,200 or 38,400 bps. (b) you're using extended memory under MS-DOS on a 286; interrupts may be lost when a 286 switches from protected mode to real mode and the 16550 prevents loss of characters along with it. (c) You're using a Perstor ARLL controller, whose long DMA cycles can prevent the CPU from fetching a byte from the UART before the next arrives. I'm sure there are more situations in which a 16550 would be helpful, but these are the main ones I've encountered. The bottom line is that the 16550 is ideal for making sure that your system isn't losing characters. If your system already isn't, then you will never notice the difference between a 16550 and whatever you replaced with it. I always have a hard time convincing people that throughput won't improve with a 16550. What it boils down to is this: the 16550 helps your CPU keep up with the data. If your CPU isn't keeping up with the data right now, you'd KNOW it. -- UUCP: watmath!xenitec!zswamp!root | 602-66 Mooregate Crescent Internet: root@zswamp.fidonet.org | Kitchener, Ontario FidoNet: SYSOP, 1:221/171 | N2M 5E6 CANADA Data: (519) 742-8939 | (519) 741-9553 MC Hammer, n. Device used to ensure firm seating of MicroChannel boards Try our new Bud 'C' compiler... it specializes in 'case' statements!
poffen@sj.ate.slb.com (Russ Poffenberger) (11/22/90)
In article <4889.274A0A5B@zswamp.fidonet.org> root@zswamp.fidonet.org (Geoffrey Welsh) writes: >Robert Nee (nee@cf_su14.Salomon.Com ) wrote: > > >1 I read in PC Magazine that in order to use a high speed > > modem at peak efficiency you must have the 16550 UART > > chip installed in your computer. (not an 8250 or 16450) > > The 16550 simply offers a 16-byte FIFO buffer in stead of a transmit hold >register and receive data register. This can be importent if (a) you're using >an XT which can't process the data quickly enough, and which loses bytes >occasionally because of it (the 16550 stores up to 16 bytes, to be fetched >whenever the XT gets around to it); this usually happens at 19,200 or 38,400 >bps. (b) you're using extended memory under MS-DOS on a 286; interrupts may be >lost when a 286 switches from protected mode to real mode and the 16550 >prevents loss of characters along with it. (c) You're using a Perstor ARLL >controller, whose long DMA cycles can prevent the CPU from fetching a byte >from the UART before the next arrives. > > I'm sure there are more situations in which a 16550 would be helpful, but >these are the main ones I've encountered. > > The bottom line is that the 16550 is ideal for making sure that your system >isn't losing characters. If your system already isn't, then you will never >notice the difference between a 16550 and whatever you replaced with it. > > I always have a hard time convincing people that throughput won't improve >with a 16550. What it boils down to is this: the 16550 helps your CPU keep up >with the data. If your CPU isn't keeping up with the data right now, you'd >KNOW it. > > Also note that I heard that these "features" of the 16550 are TURNED OFF by default at power on, and must be specifically enabled. If you don't have a driver or comm program that can do this, you will not notice any benefit. Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254
feustel@netcom.UUCP (David Feustel) (11/22/90)
Is the 16550 pin compatible with the 8250? -- David Feustel, 1930 Curdes Ave, Fort Wayne, IN 46805, (219) 482-9631 EMAIL: netcom.uucp
john@jwt.UUCP (John Temples) (11/23/90)
In article <131@cf_su20.cf_su10.Sbi.COM> nee@cf_su14.Salomon.Com (Robert Nee) writes: >1 I read in PC Magazine that in order to use a high speed > modem at peak efficiency you must have the 16550 UART > chip installed in your computer. Simply installing a 16550 won't buy you a thing. You have to have software that can enable its FIFO mode before you will see any improved performance. And if you're running in a single-tasking environment on a sufficiently fast computer, I don't think you'll see any benefit from a 16550 anyway. >2 This 16452 chip is in a socket but it is not of the DIP > variety. I don't know what to call it except that it is > is a square socket like the ones 80387sx fit into. Do > they make 16550s that fit into these square sockets. My National Semiconductor data book shows part number NS16550AV as being in a "chip carrier package" -- it's a 44-pin square part. >3 If the answers to these questions we're yes. Where would > you (the experienced high-speed communicator) purchase > a replacement high-speed UART. I've bought 16550s from JDR Microdevices and Pioneer Electronics in the past, but only in DIP packaging. I don't know if they have the PCC packaging as well. -- John W. Temples -- john@jwt.UUCP (uunet!jwt!john)
mju@mudos.ann-arbor.mi.us (Marc Unangst) (11/26/90)
nee@cf_su14.Salomon.Com (Robert Nee) writes: [Various questions about the 16550] > P.S. the computer is a DELL 310 if that helps anyone... As I recall, the Dell 310 has the serial ports built into the motherboard -- which means it's unlikely it has anything even remotely resembling an 8250, 16450, or 16550. More likely than not, it's got some sort of VLSI chip that has the UARTs, the "glue" chips, and everything else necessary for serial and parallel ports in it. You aren't going to be able to replace this with a 16550, because you'd be replacing your entire I/O subsystem, more or less. My advice would be to stick with what you have, if it works. If you start losing characters at high speeds, then your only choice will be to disable the ports on the motherboard and buy a separate I/O card with a 16550 on it. -- Marc Unangst | mju@mudos.ann-arbor.mi.us | "Bus error: passengers dumped" ...!umich!leebai!mudos!mju |
mark@typhoon.ucar.edu (Mark Bradford) (11/27/90)
In <6Dk8s3w163w@mudos.ann-arbor.mi.us> mju@mudos.ann-arbor.mi.us (Marc Unangst) writes: >nee@cf_su14.Salomon.Com (Robert Nee) writes: >[Various questions about the 16550] >> P.S. the computer is a DELL 310 if that helps anyone... >As I recall, the Dell 310 has the serial ports built into the >motherboard -- which means it's unlikely it has anything even remotely >resembling an 8250, 16450, or 16550. More likely than not, it's got >some sort of VLSI chip that has the UARTs, the "glue" chips, and >everything else necessary for serial and parallel ports in it. You >aren't going to be able to replace this with a 16550, because you'd be >replacing your entire I/O subsystem, more or less. As a matter of fact, I've done just this upgrade on a Dell 310. It turns out that the 16C452 is a combination of 2 UARTs and a parallel port, and there >IS< a 16C552 that will replace it. (I got mine from Western Digital.) Caveat emptor -- I ran the 16550.EXE program I found on a local BBS to enable the FIFO buffers, and it claimed to work, but Kermit and Procomm Plus didn't really seem to know what to do with it. But just using the 16C552 instead of the 16C452 cured my dropped character problem, even without explicitly enabling the FIFOs. I have >heard< that Western Digital 16550As have some sort of problem that National Semiconductor 16550s don't, which may carry over to the 16C552, but this may be just rumor. Your mileage may vary. -- Mark Bradford (bradfrd2@ncar.ucar.edu) <> To err is human, to moo bovine.
john@jwt.UUCP (John Temples) (11/28/90)
In article <mark.659669162@typhoon.ucar.edu> bradfrd2@ncar.ucar.edu (Mark Bradford) writes: >I have >heard< that Western Digital 16550As have some sort of problem >that National Semiconductor 16550s don't I have three of the WD parts and one NS part in my Digiboard. I have yet to notice any anomalies from the WD chips. -- John W. Temples -- john@jwt.UUCP (uunet!jwt!john)
caf@omen.UUCP (Chuck Frosberg WA7KGX) (11/29/90)
In article <1990Nov28.040535.7891@jwt.UUCP> john@jwt.UUCP (John Temples) writes: -In article <mark.659669162@typhoon.ucar.edu> bradfrd2@ncar.ucar.edu (Mark Bradford) writes: ->I have >heard< that Western Digital 16550As have some sort of problem ->that National Semiconductor 16550s don't - -I have three of the WD parts and one NS part in my Digiboard. I have -yet to notice any anomalies from the WD chips. --- -John W. Temples -- john@jwt.UUCP (uunet!jwt!john) Early WD chips have problems transmitting at slow speeds (< 4800 or so). I haven't heard of a fix yet other than disabling the FIFO. Chuck Forsberg WA7KGX ...!tektronix!reed!omen!caf Author of YMODEM, ZMODEM, Professional-YAM, ZCOMM, and DSZ Omen Technology Inc "The High Reliability Software" 17505-V NW Sauvie IS RD Portland OR 97231 503-621-3406 TeleGodzilla:621-3746 FAX:621-3735 CIS:70007,2304 Genie:CAF