[coreboot] Thin Client Compaq Evo T20

[Philip Loewen]

I'm thinking about trying coreboot on the Compaq Evo T20 
thin client. This is a Geode GX1 machine with CS5530 
companion chip and National Semiconductor DP83815 ethernet 
card. It has 48MB of flash memory and 64 MB of RAM 
(soldered). The superiotool from coreboot can't find any 
evidence of super-I/O. The mainboard contains a chip that 
looks like a socketed PLCC BIOS chip, Winbond 29C020... with 
a sticker on top giving credit to Wyse Tech 01'V9.0. The 
keyboard and mouse use a USB 1.1 interface. `lspci` says
00:13.0 USB Controller: Compaq ... ZFMicro Chipset USB (rev 06)


Expert advice on these questions would be very welcome:

1. Does coreboot support this setup? (Particularly the USB 
devices?)

2. What advantages will coreboot offer over the 
manufacturer's original BIOS? E.g., will I get a BIOS 
control screen I can use to change settings until they work?

3. I don't have too much time to indulge in hardware 
hacking. I'm hoping for an approach that would not require 
me to even open the Evo's case! And this might be possible: 
like the Wyse Winterm, the Evo boots from on-board flash 
memory that can be rewritten using 'netxfer'. One of the 
files that netxfer delivers to the thin client is called 
"the BIOS" by people who know these things. Tradition among 
users like me is to treat that file with great respect, 
making sure an exact copy of the factory original is present 
whenever other files in the bundle are replaced. Here's my 
main question: can I replace that file (named ulc_code.ce, 
size 4 MB) with something from coreboot and use 'netxfer' to 
get a working alternative to the factory BIOS? What can I 
test before trying this to make sure I don't turn my little 
device into a brick? Are there some magic bytes or 
signatures to look for in the factory-file to confirm that 
it really is some kind of BIOS, and that program execution 
starts from the same location in the commercial file as it 
will in coreboot? What else should I be watching for?

Thanks in advance for any comments or pointers.

Philip