HomePlug AV is a standard for transmitting ethetnet packets via power outlets. Second edition of initial HomePlug standard with almost 200 Mbit rates in theory and about 40-80 Mbit in practice (~ 5-7 Mb/s).
http://en.wikipedia.org/wiki/HomePlug
So, all the HomePlug AV devices in the world are made by Intellon Corp. (the division of Atheros right now). There are many brands on the market, that sell devices with Intellon/Atheros chips inside. There are a lot of firmwares also. Most of them can be installed on HomePlug AV devices from different brands.
The name of chip can be viewed by various number of utilities from different manufactures. Usually it's signed as INT6xxx-MAC-...
For example:
INT6300-MAC-3-0-3052-1120-20070816-FINAL-B
-- INT6300 is a chip,
-- 3-0-3052 is FW version,
-- 20070816 is a date.
To work with HomePlug AV you need an utility to set up Private Network Name and viewing current rates. I recommend WD Livewire Utility 1.0.3 build 005 (can be downloaded via their site). You can also upgrade/downgrade FM of device via this utility. To do it you need to connect HomePlug AV device directly (locally) to your PC/laptop and press "Upgrade Firmware" button. The asked files:
PIB -- control file (offsets, tones, region etc., don't bother),
NVM -- FW file.
You can find these two files in archive of actual FW to your device from the original or any other manufacturer's site.
For example:
int6000-400-cord6ft-HomePlugAV_CE.pib (CE -- for Europe, NA -- for North America)
int6000-v3.0.5-0-2-B-FINAL.nvm (B -- for Europe, C -- for North America and Japan)
So, to tweak your HomePlug AV device you need another utility from the Intellon -- INT6x00 Device Manager. The only version you can find in Internet is 3.0.3032. And it works only with FW 3.0.5 and below. So, you can upgrade to newest FW, but in this case you can't tweak your device, because there is no new version of Device Manager for free download in Internet.
I found version 3.0.3032 here:
http://www.cpx.cz/dls/wodaplug/Executables.zip
The "tweaking" process requires knowledge of network and HomePlug AV specification. So, if you are not in subject -- don't even touch it. I'm serious. Here they are, the famous delusions of all newbies:
1. New FW = better work and speed. NO. And don't ask why. Just know. If you want more details -- read the release notes of the FW carefully. Notice that chip has your device, google and read enough info about it before you decide to press "Upgrade" button.
2. The 4 digits code on the case is important. NO. It's useful only for remote control of the device via utility (WD Livewire Utility, for example). If you try FW from another manufacture your device can lost its original MAC and that 4 digits code..
3. You can brick your device by up/downgrading. YES, you can, but the chance is veeery low. Sometimes you can receive this for your new MAC: 00:b0:52:00:00:03. This MAC shows that your device in trouble (PIB and NVM installed are different). But even in this case you should try to set up the device via Utility (not Device Manager, Utility). Try and if it's working -- just relax. Even with 00:b0:52:00:00:03 your device will work in the PowerLine Network. The only difficulty will be setting Private Network Name (PNM) for this device locally (i.e you should directly connect it to the PC/laptop and set PNM), because your original 4 digits code was deleted from the device memory.
If MAC changed to 00:b0:52:00:00:03 and device don't want to wark with another HomePlug AV you can try to downgrade it to FW version 3.0.5. And after it -- upgrade to any different new version. There is some chance that new MAC of your device will change from 00:b0:52:00:00:03 to normal.
And about speeds. The best result I heard about was 10 Mb/s. The results that I got personally: 4-7 Mb/s. It's better than wi-fi 802.11g, but it's worse than wi-fi 802.11n. And remember that in case of using HomePlug AV network you should avoid using electric devices that can create current noises in Power Line Network (drill, halogen lamps, hairdryers etc.). They can dramatically slow down the performance of the HomePlug AV network.
So, that's enough for the beginning :)