I used to play about with 'tweaking' my connection back in my dial up days. Though things might have changed since then.
Some of the tweaks I remember:
- Using FreePPP software instead of OS 9's built in dialup software. (no longer applicable in OS X)
- Trial and error with different modem scripts. Some are manufacturer specific, but some are more general and may work better/worse.
- If you're on a noisy line it can be better to connect with a slower modem script, as if you had a 33.6k modem.
- Play about with different browsers and browser settings. There is a trick to get Safari to start displaying a page sooner at the expense of a slighter longer rendering time (might be more useful to do this on dialup than broadband)
http://guides.macrumors.com/Speed_up_Safari See the last tip.
- Onspeed and the like, can help a little bit but i've always been suspicious of these systems. Don't believe the figures they quote you.
- Monitor your actual connection rate. Not sure where this figure will be but whenever you 'dial up', a connection rate will be established. If it's quite far off 56k it might be worth checking your modem cable, extension cable and general phone line wiring. Also ask your phone provider if they can measure the lines performance - It may be possible for them to increase gain/'tune up' the voice line, therefore providing better connection speeds.
- Your built in modem may be 56k but is it v.90 or v.92 ? As far as I know, the latter provides an upload speed equal to download. If you're really really desperate, it might be possible to find an external USB modem that supports v.92.
- If you are using any P2P software or upload on a regular basis, consider 'throttling' your upload speed. For example, with Bittorrent I find that even with a maximum upload speed of 45k/sec at my disposal, it's best to limit uploads to 20-25k/sec. This leaves space for 'acks' to be sent back cleanly (whole other subject!) and can boost download speeds. With 56k it would require much trial and error! One way to do this is by monitoring your upload and download speeds via a graph - If it's 'spikey' it might be worth reducing your upload speed a notch or two. There's a program called Throttled that will let you customize upload speeds for any program -
http://www.intrarts.com/throttled.html Getting this right is almost an art form in itself, so for it to help with a dialup connection would be worth a standing ovation! I'd say this could well be a shot in the dark.
That's all I can think of at the moment. Even if any of the above helps, don't expect any miracles!