Up FIFO buffer settings!



We get some calls from people saying that they are having troubles keeping their modems connected.  There are many possible causes for this.  I generally recommend that people make certain changes from the standard modem set-up configurations because of these potential problems.


Before you read any further you should know that this article is written for the layman.  If you know what a modem initialization string is you would be better served to read the information posted at the 56k modem users site at : They will even tell you which modems have bugs, etc...  and how to fix them.  A much better source for debugging modems.  This page gives you some windows based work-arounds for common modem problems.


Modern modem circuits were designed for computers that operated in the 40 to 100 mhz speed range.  Modern computers CPU's work much faster and as a result they can literally suck the modem cache dry.  Caches usually need to primed in order to maintain data flow, meaning they need stuff in them to work.  As computers have gotten faster more and more people are complaining that "their ISP disconnects them after they've only been connected for a couple of minutes".  This is a wrong assertion.  The dial-up centers could care less about trying to disconnect you, they get paid for keeping you connected and providing good service.  However, they will disconnect you if the line condition becomes bad (i.e. to much static to understand the data stream - which can result from anything from bad weather, roadwork, to not transmitting anything). 

Generally I tell people there are two really good things to try if this is happening to them.
First,  Reboot your computer.  One analogy for modems says that they are hard thinkers, very single minded and can get just as confused as the people who created them.  This happens with all modems.  If you make it a habit to leave your computer on all the time, it will happen more often to you.  More expensive modems have this happen less often (Except some Diamond modems have inherent bugs which cause this problem).  This is because they have larger cache's which allows them to be "confused" and operational at the same time.  Unfortunately modems don't have reset switches and the only way to give them a true fresh start is to reboot.
Second, Adjust the Buffer Settings: People resist this procedure because they think it will make their modem work slower, but it will actually feel like it's working faster, trust me...  follow the directions on this link : Modifying the FIFO cache setting
If it feels to you like your ISP is disconnecting you before your timeout period is reached then one of the following is probably occurring:


1)    Bad line condition :
                Did you just have another line added to your house?
Often the phone company will piggy back your single signal on both lines in your house to improve line quality, however when you add a line they have to split the two signals with only one per extension.  You should try your computer on both lines to see if the service is better on one than the other.
               Did you change plug-in locations?
The wall wiring is not always optimum in every room.  You may simply have some wiring in your house that isn't modem capable.
                Did you change some phone extension cords

Store bought extension cords for phone lines work OK for voice signals but are poor for modems because they seldom use good emf shielding practices.  I pulled one of these lines apart once. I was having trouble with it and found they didn't even use "twisted pair" type field canceling wiring practices.  If you are buying an extension cord specifically for a modem use, make sure that it says it will work for a modem.

Bad line condition can also result from no transmission occurring.  Have you ever sat on the phone talking to someone and they put the phone down to yell at the dogs or something?  Listen carefully to what happens to the signal.  Over time it will degrade (get static) or get interrupted (some phone systems assume that you wouldn't be connected if you weren't saying something every so often, so if you're quite they think they may have a problem and try to repair your connection.  Modems interpret this action as a lost signal and disconnect.  Surprisingly, the modification to the FIFO settings does fairly well at compensating for stalled conditions and static interruptions.

Do you have call waiting.  Most modems have a feature for disabling your call waiting before they dial.  This doesn't always work.  When it doesn't an incoming call will disconnect you, not only that, but you'll never know you had an incoming call either, because the modem intercepted the signal.  Make sure your modem is correctly disabling your call waiting if you have it.

Finally, if you've tried it all and your still having troubles, try a different phone number.  We often offer more than one local number for each area and the phone company may route you through some aged equipment to get to one number and not another.

2.        If your modem is timing out due to inactivity: This is almost always an indication that your internal modem cache is confused and cluttered with bad data.  When this happens you'll have little or no room for good data to pass through and even when it does you'll quickly empty the cache and the modem will most likely time-out again.  The modification to the FIFO buffer settings will improve this situation and cause it to occur much less often, however, there is only one way to fix a confused modem... REBOOT! (Actually there are others, but they are more advanced than this article is intended to get).

Another excellent resource for 56k modem trouble shooting is   Also try :

Give them a try, they've documented most modem problems I've heard of.  If you have any questions about this e-mail me at

Thanks for reading...