It was determined that this needed to be posted here on AppleFritter as well in the event that there might be a 'FritterCritter poking around who may want to get involved. 
My post on 68kMLA:
Protocol7 and I traded quite a few PMs on this one.
Summary:** There is macbootable Sil3112 firmware. FirmTek SeriTek/1s2 is the card. aka Sonnet Tempo SATA (TSATA). These cards can boot pre-G3 PowerMacs and boot 7.6.1.
See here:
http://www.sonnettech.com/support/kb/kb.php?cat=343&expand=_a2_b37&action=b206#b206
206 The Tempo SATA card does not seem to work properly in my Power Mac G4. Do I need different firmware? Apr-25-10Some customers have experienced problems with the current version of the firmware in older G4 machines. Sonnet suggests downgrading the firmware to the Version 5.13, which can be found at http://www.firmtek.com/download/SeriTek1S2_513.zip
** newest recommended FirmTek firmware (5.13) is 136k. This is too big to fit on any Sil3112 card currently tested and also a crossflashed Sil3512 based card. FirmTek firmware 5.11 is 131k, still too big.
Either need to find a bigger chip to solder onto the card or reduce the size of the firmware or find a card that has a bigger chip already. Protocol tried multiple times to reduce 5.13 it but no luck yet.Not sure if he tried with 5.11 since then though.
(The Silicon Image updates are 128k, Weibetech's are only 64k, but we need the FirmTek one)** There was an OS9 flasher mentioned in a MacGuru article. It has not been located yet.(hoping that it might come with a smaller fimware file)
Props to Protocol7 for his legwork searching the vast internet and editing the ROMs.
And RIP to the new-in-box 3.5" floppy disk I seem to have killed with all the flashing activity.Protocol7, if I have missed anything or if you have updates please post it.
To others, if you want to try to reduce a firmware or have a card that can take a full-size FirmTek firmware please let it be known. :)
And some additional info posted by protocol7 that looks like it may have significant potential!:
There's also a Japanese card that uses the Sil3112 and appears to only have a 512kbit eeprom (64kB firmware file). Finding a firmware from that would be immensely helpful. I can't say with any degree of certainty that the Mac cards are otherwise identical to the PC ones. It'll take a suitable firmware file to find out for sure.
So that is about that. In the PC world You see people crossflashing Sil3512 and Sil3112 cards so if you can only get one, you may still be in luck.
Not really sure what else I should add here, but if you have any questions or comments please do post. 
Thanks for posting this information!
The flash chip on these cards is a common SST chip, and it's large enough that swapping it out wouldn't be too difficult. There's always the toaster oven method for those lacking a reflow station.
The possibility of flashing a cheap SATA card and being able to use it on a PCI Mac all the way back to OS 8.6 is really interesting. Has your research so far discovered which bios versions work with classic MacOS? I followed the Sonnet reference to the 5.13 Firmtek driver, but wondering if since the archive contains a .dmg how much pre-OS X compatibility it offers.
I'll have to consider my budget, but if I decide to experiment I'll post any results here.
Well, I am not sure what the oldest version of Mac OS that firmware v5.13 supports exactly but people have reported using the Sonnet TSATA in pre-G3 PowerMacs running System 7.6.1. There would also have been some upset customers if FirmTek just axed compatibility with older stuff.
I can say with relative certainty that we will not be seeing this issue.
Having to use OS X to flash it is not relevant in this case as far as I am aware.
I've got an Adaptec SATAConnect 1205SA card in an old PC. According to the message at boot time, it is based on the Silicon Image 3112A.
Any possibility that it might be flashable to the Mac?
If you find out how big the EEPROM is then you can make a better determination.
A thread over on the 68k MLA mentions that a card called the WiebeTech TCS1-1 is Sil3112-based and bootable under Mac OS X. Looking at the firmware, it appears to be on 32K in size.
Do you have any experience with flashing the WiebeTech firmware to a 3112?
TSC1-1 = 3512
TSC2-0 = 3112
I personally have not tried the TCS2-0 firmware. It *should* be pretty similar to the 1-1.(I do not have any 3112 cards)
If you have a 3112 card and want to try it then go for it, but unless it allows for booting and use of the drives in OS 9 it is not the holy grail of SATA card flashing for old Macs.
I should also say that if it is anything like the 1-1 flasher, it *should* come with the PC firmware as well so you can revert the card for PC use.(unless your flashing goes horribly wrong and your machine hangs or loses power or something)
ymmv, check it out first before flashing if you care.
anyone else working on this?
i had the idea that, this firmtek firmware is known to be larger then the 128k or 64k sizes on some sil3112 2xsata 32bit cards
but what if we could remove the osx kexts from the size of the chip?
my interest is getting more os9 bootable sata cards.... there are other cards that are able to boot X with the weibetech firmware amirite?
but what is really needed is the os9 bootability... even if i had to reflash the card to go between the functionality of 9 + x this would indeed
be more easily accomplished then to rip off the bios chip + resolder a new compatible chip.. as some of us do not possess the skills
required to do so;)
can we discuss potential methods for reducing the rom?
does anyone know which SIL3214 card will boot mac os 9?
i saw another post by Oelmuvun claming that the FirmTek SeriTek/2SE4
used the SIL3214 chipset.. but then i checked "Compatibility" of this model
the "2SE4" is meant only for use with g5 macs..
http://eshop.macsales.com/item/Firmtek/SATA2SE4/ (click compatibility)
so the answer i seek is, is there any g4 mac compatible
4-port sata cards that are mac os 9 bootable that
utilize the SIL3214 chipset? i also read that that Seritek 1V4 doesnt use this
chipset at all instead uses a chipset by a company called "VITESSE"
anyone have any further info? ultimately im looking to see if silicon image 3214 cards
can be flashed with firmware for mac os 9 booting.. because it was determined
over on macos9lives.com that these 64bit cards, even operating
at 33mhz offer up to 266mb/s which is a huge improvement over
the 133mb/s top level of a 32bit card operating at 33mhz
see these threads for more info:
http://macos9lives.com/smforum/index.php?topic=803.0
http://macos9lives.com/smforum/index.php?topic=825.0
http://macos9lives.com/smforum/index.php?topic=306.0
i flashed pc, pci sata card-it function on g4 mac.