I have done a lot of googling and have discovered the following:
If you have upgraded the sawtooth firmware (aka boot rom) using the 4.x update, the ability to boot into 8.6 is disabled.
This brings up the question of what sawtooth firmware versions support 8.6 booting. According to a Japanese site I found, the original 8.6 sawtooth shipped with firmware version 1.2f1. The first OS9 sawtooth shipped with 1.3f1. Later sawtooths shipped with 9.0.2 or 9.0.4 and there was a big jump in the firmware version to $0003.22f1, $0003.24f1, and $0003.26f1 (as reported by Apple System Profiler). The Japanese site seems to imply that firmware versions 1.2f1 to $0003.24f1 support 8.6 booting. Most people refer to $0003.24f1 as firmware version 3.2.4 which I believe is correct. However, here is where it gets confusing. The first firmware update for the sawtooth that apple made publicly available was firmware update v2.4. The Japanese site seems to imply that if you try to run this update on a sawtooth with firmware $0003.26f1 (v3.2.6) you will get a message saying the 2.4 update is not needed since there is a newer version. This leads me to believe that the 2.4 update is probably the same as $0003.24f1. In any event, I can definitely confirm that the v2.4 firmware update still allows 8.6 booting. In another discussion, I found a sawtooth owner who did in fact apply the 2.4 update who states he now had the ability to boot into 8.6, 9.0 and OSX.
The next question is whether you can restore 8.6 booting if you have in fact upgraded your firmware to v4.x. I can think of two possible solutions:
1. Perhaps it would be possible to write an Open Firmware patch/hack that somehow overrules the apple firmware and restores 8.6 bootability. In my google searches I can find no evidence that anyone has tried this so I dont know if is possible. In any event, it would require someone with lots of knowledge about hacking Open Firmware and there appears to be very few of those persons around.
2. The second and more likely solution is to reflash the sawtooth firmware to revert back to an earlier version that does support 8.6 booting. Of course in order to do this we would need some type of utility that would save a copy of the needed older 8.6 boot rom as well have the ability to flash the boot rom chip. My google searches do confirm that such utilities do exist but they may be hard to obtain. Here is what I have found out about these flashing utilities:
It appears that Apple had such a utility. I found a Pismo user who had a corrupt boot rom. He stated a friend gave him a Apple service CD that had what he called a boot rom reader/updater. This utility allowed him to save a copy of the boot rom from a good pismo and then using that saved copy reflash the bad pismo. In the end, he wasn't able to do it because the service cd had a 9.0 system folder that wouldn't boot on his pismo. It would be great if we could get this utility. Perhaps if members of this forum who have old apple service CDs could dig them out and see if they can find what this guy is talking about. The strange thing is, I am somewhat familiar with Apple service CDs from this era, the MacTest Pro CDs, and I don't recall these CDs ever having such a utility so I don't know what Apple diagnostic CD this pismo owner is referring to.
However, I have discovered other similiar utilities that may be easier to obtain. It appears that most of the cpu upgrade companies have these flashing utilities that they appear to be willing to make available to customers. For example, in a discussion on the apple support forums I found a Sawtooth owner who had a corrupt boot rom who wanted to reflash it with a fresh copy of the firmware. He stated that Sonnet sent him a utility he called the G4 ROM Utility that had the ability to both save a copy of the boot rom and reflash it. Of course, this guy was sort of in a catch 22 situation. He had the utility to reflash his sawtooth but he didn't have a copy of the boot rom. Since we have already seen at least one 68kmla member who is still running 8.6 on a sawtooth, if we could ever get a flashing utility, we could get that member to use it to save a copy of his 8.6 bootable firmware which we could then use to reflash other Sawtooths. (As an aside, there are several utilities that are available for saving copies of the boot rom of macs mainly for use among mac emulator users such as sheepshaver and basilisk. Some of the ones I know about are AutoCopyROM, CopyROM, and GetROM. There may be a few others. To the best of my knowledge none of the rom savers support flashing. In theory, we could also use one of these rom savers to get a copy of the Sawtooth 8.6 compatible boot rom. However, I dont know if the resulting saved rom file would be compatible with a firmware flashing utility).
I have also seen evidence that the other cpu upgrade companies may have had similiar flashing utilities. For example, on the Daystar/XLR8 support forum, a user wanted to reflash his firmware to remove the special patches the cpu upgrade applied to his firmware. Daystar responds by saying he should email support and request a firmware remover. They say it is a manual tool that allows you to reflash the original apple firmware. Though they don't say if it also allows you to save a copy of the firmware, I wouldn't be surprised if it does. Powerlogix also had a tool that allowed you to save a copy of the boot rom and then reflash it. In fact they made this tool publicly available. It was intended for use on only the PowerBook G3s and iMacs with their BlueChip upgrade for those macs. On those macs, the boot rom chip is located on the oem cpu card which is removed when you install the cpu upgrade. Therefore, before installing the BlueChip upgrade you had to use the flash utility to save a copy of the original firmware. Then after installing the BlueChip upgrade, you had to use the flash utility to write the firmware to the boot rom chip on the upgrade card. You can still download this flash utility from the Japanese Powerlogix site. The only issue with this is whether you can run the flasher on other macs. If not, can it be hacked to allow it to run on other macs.
Lastly, even if we can't get a copy of any of these flashing utilities, there may still be one possibility to reflash the firmware. Over on the cubeowner forum, a user named Pareis has discovered a way to use Apple's own publicly available firmware flashers to reflash the firmware to an older version. Here is a quick summary of what Pareis discovered:
As anyone who has used Apple's G4 firmware updates knows, they require you to boot into OS9 in order to use them. This presents problems for users who only have OSX installed and no longer have copies of a OS9 system folder. Pareis wanted to find out if there was a way to install the firmware update without booting into OS9. He did. He discovered that the firmware flasher itself runs under Open Firmware and that you could bypass the OS9 installer application. All the OS9 installer application does is to check to make sure you are running the right mac and whether the firmware version is newer. Pareis discovered that you can bypass this OS9 installer app by copying the included firmware file to the hard drive (or even burn the firmware file to a blank CD) and then boot into Open Firmware and choose the firmware file as the boot device which results in the flasher running and updating the firmware. He even wrote an OSX script to help automate this procedure. This led another user to ask since the firmware version check is bypassed whether it would be possible to run an older firmware update to in essence revert back to an earlier version of firmware. Pareis discovered you can. In fact, on his sawtooth he was able to successfully downgrade the firmware from 4.2.8 to the older 4.1.8 and then back to 4.2.8 again. This makes me wonder whether the same thing is possible using the older 2.4 firmware update that we know supports 8.6 booting. That is, try to boot into Open Firmware using the 2.4 firmware file as the boot device to see if we could bypass any version checks to revert back to this older firmware. However, Pareis hints that this may not be possible. His further analysis of the code in the firmware file shows that it will only flash a firmware with the same major version as in the ROM (That is, you can reflash from say 4.2.8 to 4.1.8 but you can't flash from 4.x down to 3.x or lower. However, you can upgrade from 3.x or lower to 4.x). He does not state whether it is possible to hack the firmware file to bypass this version check. This leads me to believe that it may not be possible to use this technique to try to downgrade the ROM from 4.x to 2.4. However, it may be still worth a try just in case Pareis is wrong.
As an aside, this guy named Pareis seems to be one of the few people I can find who seems to be a somewhat of an expert in using Open Firmware. It would be interesting to try to contact him about the problem of Apple removing the ability to boot into 8.6 to see if he could come up with some type of simple Open Firmware hack that would restore 8.6 bootability.
That is all I know about and more than anyone would probably want to know about Sawtooth firmware versions and the ability to boot 8.6
