Linksys WRT54G v1.0 & 1.1
From DD-WRT Wiki
 How To Flash
NOTE: During configuration or while writing to Flash memory, the only things that should be hooked to the Linksys WRT54G router are the computer and power.
[Comment --n8hfi: On a very old WRT54G v1.0, I found it necessary to upgrade with a newer Linksys firmware before I could load DD-WRT. The original firmware (Linksys v1.00.8 Dec 24 2002) gave a "incorrect image file" error on on both the mini and standard DD-WRT v23 SP2 images. The following sequence was performed with the HTML GUI and Microsoft Internet Explorer Web browser:
- Restore factory defaults with the original firmware.
- Upgrade to Linksys firmware version 4.21.1. You can get it here. Read the fine print carefully, as not all firmware versions work with all hardware versions.
- Upgrade to DD-WRT v23sp2_mini_generic. I got the Continue page, but never got the DD-WRT GUI.
- Hold the reset button for 30 seconds (I didn't cycle power or anything else on the router.)
- Then I got the DD_WRT GUI. I reset it to factory defaults with the GUI, although this step may have been unnecessary, since I'd just flashed it.
- Upgrade to DD-WRT v23sp2_standard_generic. I selected the "restore factory defaults after flashing" option while doing this.
- all set [Comment from jas3 on 16-Mar-2008: The above worked for me. I then updated from standard to dd-wrt.v23_vpn_generic.bin, which succeeded as well]
After every firmware upgrade, perform a full reset by depressing the reset button for 30 seconds on power-up. Failure to do so after an upgrade will result in unpredictable router behavior.
 Other Notes
[redhedjim: 2013-09-01 WRT54G v1.1 with recent Linksys firmware] Signed on to the Linksys, did a factory reset. Used the web browser to upload a mini-Generic release (happened to be build 13064, from the Router Database page). Router rebooted to DD-WRT (that was easy!). Did a 30-30-30 reboot, and DD-WRT was running. Uploaded the std_Generic build (also 13064). Found that odd things happened from to time, and the site survey did not work. Re-read the Peacock post, 13064 is not a good release - DO NOT TRUST THE ROUTER DATABASE to recommend a release. Did a telnet into the router to determine corerev (see Peacock step 4, nvram get wl0_corerev) to confirm that corerev=4. Therefore, I needed a VINT build. I used EKO VINT 12548, and everything was rosy. Then tried EKO VINT 13491, and again everything was great.
SUMMARY: Use the Linksys web interface to FIRST install a generic mini build, then 30-30-30. Then install a VINT EKO standard build (or any other build that fits), I had best success with 12548 and 13491. 30-30-30, and then do your detailed configuration. I have tested Site Survey, AP, Client, Client Bridge, and Repeater Bridge, all work fine. I have not tested VOIP, OpenVPN, etc., so do not know if these work in the build numbers listed above. [end redhedjim]
[dgb: 2009.04.25 V1.0 hardware with 1.02.1 firmware] On a V1.0 box with firmware 1.02.1 Feb 2003... First there is no administration tab, look under "system". With IE and eventually with Firefox pushing the Upgrade button resulted in a chooser (browser). I choose the dd-wrt bin file and pushed the Upgrade button, the browsers each failed. IE reported the server was busy or not available. Firefox sent a dump off to microsoft. So I located and tried to install a newer linksys firmware load - same results. I then loaded up netscape, turned off the blockers, configured it to open popups in a new tab, choose the newer linksys firmware and pressed update. It showed a progress bar as the firmware was loaded into the vintage box, Eventually the page went blank on "http://192.168.1.1/upgrade.cgi". Lights occasionally flicker as I impatiently wait and document the differences I've seen to this point.
I now have linksys FW revision v4.21.1 and an Administration tab...30/30/30
Still using NS and under Adminstration/Firmware Upgrade I selected the dd-wrt load dd-wrt.v24-9517_vint_voip, an upload progress bar displayed followed by "upgrade are failed!", I choose continue... Repeating the process has the same result. Third attempt, this time with IE - same result. I surmise that the router is not actually attempting to flash itself, but failing the .bin file. This for two reasons, the progress bar never gets much past 50% and the router never 'goes away", in fact it reports and error and wants to continue. The progress bar actually completes once then starts again before the failure notice.
Now I'm guessing here, but maybe some sick firmware developer who wasn't even in college when v1.0 hardware was available coded in an assert that the .bin file must be able to fit within the smaller modern architectures. I used IE to get the linksys firware to use dd-wrt.v24-9517_VINT_mini and "Upgrade is successful" from the unit. Pressed "continue" presented root/admin and here's my old friend dd-wrt! I can feel a new wireless bridge being born... 30/30/30 more Scotch, more beer.
Still using IE and using the dd-wrt upgraded to the desired ...voip load I wanted all a long. 30/30/30...
The old box is now running dd-wrt v24(05/20/08)voip uptime 1 min. There probably isn't a lot of this old stuff out there so maybe this isn't of interest to anyone else - but if you're trying, get netscape for that first giant step... [end dgb]
(start ghz24) wrt54g ver 1.1 Initial flash went without hitch but when I upgraded to dd-wrt.v24-15280_VINT_openvpn_jffs_small.bin the router lost it's wired switch (no ip add.) no ping response to a manual assigned ip # . But the wireless worked for 5-10 minutes at a time so I took a chance and upgraded via the wireless connection as a next/ last resort it actually worked reverted to dd-wrt.v24-12548_VINT_openvpn_jffs_small.bin switch works again (maybe 15280 is to modern of a build for this router ?) The 15280 build is flawless on 2 of my ver 2s (end ghz24)