I guess the main trick would be to figure out if the original bios with the scsi bios sets some pin to en/disable the scsi chip after which the scsi controller becomes available to the system and the scsi bios has actually any use.
So, figure out what en/disables the scsi device and incorporate the scsi bios .

I tried different method. The SCSI OpROM was extracted, modified and inserted back into the original BIOS image.
So when the modded SCSI ROM runs its code modifies 52h register setting bit#2 into "1".

P.S. Thanks pinczakko for his book and IDA scripts

Thanks a lot! I just tried this one and there seems to be no difference to the original BIOS. Something in the BIOS code seems to override all changes done by other parts of the code.

Meanwhile I tried several AWARD HX-BIOSes without SCSI BIOS that support the SMC Super I/O 669QF-P. It´s a pity most top HX boards have Winbond or UMC Super-IOs, only a few use the SMC chip.

There´s one for the DFI G586IPC that hangs at startup.
The one for ABIT AB-PN5 fails initializing the Floppy interface
The first release for ECS P5HXA won´t work 100%, later versions hang at start
The first release for the ECS P5HX-LA works, but it´s from 96 and crammed with ATI graphics BIOS and other stuff- later versions fail to initialize 512K Cache + 11bit TAG completely, they all hang at "BE-07".

Finally I tried ASUS P\I-XP55T2P4. It´s from 1998 and enables 512MB cacheable area automatically without the need to set the switch in BIOS setup. I could not find any issues so far!
I`ll try a Windows install next and see if the onboard scsi chip is detected. In the BIOS summary it is, but there´s "N/A" under IRQ.
The onboard SCSI chips I know are tied to a specific PCI slot IRQ / INT wise - I think BIOS must accomodate that in some way.

Finally a success?!? Fingers crossed!

Might have to remap the irq/pci lines or whatever. 🤔 might be looking for it on the wrong slot.

majestyk wrote on 2022-11-13, 15:29:

Thanks a lot! I just tried this one and there seems to be no difference to the original BIOS. Something in the BIOS code seems t […]
Show full quote

Thanks a lot! I just tried this one and there seems to be no difference to the original BIOS. Something in the BIOS code seems to override all changes done by other parts of the code.

Meanwhile I tried several AWARD HX-BIOSes without SCSI BIOS that support the SMC Super I/O 669QF-P. It´s a pity most top HX boards have Winbond or UMC Super-IOs, only a few use the SMC chip.

There´s one for the DFI G586IPC that hangs at startup.
The one for ABIT AB-PN5 fails initializing the Floppy interface
The first release for ECS P5HXA won´t work 100%, later versions hang at start
The first release for the ECS P5HX-LA works, but it´s from 96 and crammed with ATI graphics BIOS and other stuff- later versions fail to initialize 512K Cache + 11bit TAG completely, they all hang at "BE-07".

Finally I tried ASUS P\I-XP55T2P4. It´s from 1998 and enables 512MB cacheable area automatically without the need to set the switch in BIOS setup. I could not find any issues so far!
I`ll try a Windows install next and see if the onboard scsi chip is detected. In the BIOS summary it is, but there´s "N/A" under IRQ.
The onboard SCSI chips I know are tied to a specific PCI slot IRQ / INT wise - I think BIOS must accomodate that in some way.

On-Board AIC-7880 on device 8h. I will see if there is any intended way to **add** an IRQ entry to AwardBIOS. If not, it might require deeper hacking of the BIOS (chkcpu can help) to add the IRQ entry.

quick edit: asus seems to have obfuscated IRQ routing table. Modbin nor the buggy AWDBEDIT cannot even view it let alone edit. Hopefully we can find a non ASUS AwardBIOS that enables the cacheable area. Maybe you can help out with that because you need to test the AwardBIOSes on your motherboard to see if they work the same as the ASUS. Follows a list of all 430HX AwardBIOSes. https://theretroweb.com/bios/?biosManufacture … 5&chipsetId=276 A lot to try for sure... I'm sure some BIOS will work exactly as good as the ASUS but that we can edit it easier. Maybe try TMC AI5TH or AOpen AP5k.

Both Gigabyte GA-586DX and ASUS P/I-P55T2P4S do have the AIC7880 and they have AWARD BIOSes so it must be possible in some way.
In the ASUS P/I-XP55T2P4 BIOS theres a switch gor setting SCSI to "disable" or "Auto".

The routing table of the AMI BIOS can be seen / changed with AMIBCP. But that´s not helping as long as it cannot be forced to set 512MB cacheable area.

BurnedPinguin wrote on 2022-11-13, 18:54:

Maybe try TMC AI5TH or AOpen AP5k.

Or Tekram P5H30-WS (BIOS at 1999, Adaptec SCSI)

Fully “Plug & Play” compatible via an Award BIOS, the P5H30-NS/WS facilitates easy
system configuration and peripheral setup. With support for up to 512MB of System RAM,
EDO and ECC, the P5H30-NS/WS is the ideal foundation for high-end computer systems.

The Tekram sadly has a different super I/O, it also outputs "Host Adapter Config Error" when the SCSI BIOS appears.
The AI5TH won´t recognize L2 cache at all and hangs at the summary screen.
and finally the Aopen AP5K BIOS fails to address the Floppy drive and Serial/LPT ports just like it was for a different super I/O.

majestyk wrote on 2022-11-13, 20:04:

The Tekram sadly has a different super I/O, it also outputs "Host Adapter Config Error" when the SCSI BIOS appears.
The AI5TH won´t recognize L2 cache at all and hangs at the summary screen.

It's a pity 🙁
I saw photos of ASUS P/I-P55T2P4 (AT model) - different revisions have different SIOs but a BIOS is the same I think.
IMO the BIOS has code that supports both SMC and Winbond

Roman555 wrote on 2022-11-13, 20:13:

I saw photos of ASUS P/I-P55T2P4 (AT model) - different revisions have different SIOs but a BIOS the same I think.
IMO the BIOS has code that supports both SMC and Winbond

Wow! You are right!
I had just flipped through the pics of my own T2P4s and they all have WInbonds.
I´ll check if the IRQ/PCI table is editable.... -> it seems to be the same situation as with the X55... BIOS. Probably it´s the same BIOS.
But the IRQs for PCI-Slot 1,2,3,4 can be set in the BIOS setup manually (default is "Auto"). You can also set "SYMBIOS SCSI BIOS" to "Auto" or "disabled", but that´s for the ASUS SC-200 PCI SCSI card only.
.

Here´s the routing table of the original AMI BIOS:

majestyk wrote on 2022-11-13, 20:22:

Wow! You are right! I had just flipped through the pics of my own T2P4s and they all have WInbonds. I´ll check if the IRQ/PCI t […]
Show full quote

Roman555 wrote on 2022-11-13, 20:13:

I saw photos of ASUS P/I-P55T2P4 (AT model) - different revisions have different SIOs but a BIOS the same I think.
IMO the BIOS has code that supports both SMC and Winbond

Wow! You are right!
I had just flipped through the pics of my own T2P4s and they all have WInbonds.
I´ll check if the IRQ/PCI table is editable.... -> it seems to be the same situation as with the X55... BIOS. Probably it´s the same BIOS.
But the IRQs for PCI-Slot 1,2,3,4 can be set in the BIOS setup manually (default is "Auto"). You can also set "SYMBIOS SCSI BIOS" to "Auto" or "disabled", but that´s for the ASUS SC-200 PCI SCSI card only.
.
summary_screen.JPG
Here´s the routing table of the original AMI BIOS:
ami_irq_routing.JPG

Ok. majestyk, I'll pick ASUS P55T2P4SC bios , change IRQ table and attach a modding bios later.

Here it is.

Thanks 1st of all!
Which ASUS BIOS version did you use?
The modded one complains "floppy disk fail" and hitting F1 reboots the machine.
Maybe the version you used doesn´t support the SMC chip?
I used this one:

In the meantime I upgraded my FIC PT-2200, a HX board with AMI BIOS, with a second TAG chip:

There was one 128K chip present, these are hard to find, so I soldered 2 x 256K.
Then I activated the hidden BIOS menue entries with AMIBCP, activated 512MB enlarged cacheable area and - Bob´s your uncle.
The resistor that needs to be moved to switch from pulling TIO10 high to low is located between the chips.

So the PT-2200 is the first HX board I came acrooss to run fully featured HX L2 cache with AMI BIOS! (there´s also an AWARD BIOS available for this board that works also).
This is the latest BIOS version with all the switches enabled:

Then I tried this AMI BIOS in the 54TPI and the enlarged cacheable area is activated without any problems.
BUT, there´s no SCSI and, even worse, the FIC has a rare National "PC87336VLJ" Super I/O so I have to use an ISA I/O card.

majestyk wrote on 2022-11-14, 14:54:

Thanks 1st of all! Which ASUS BIOS version did you use? The modded one complains "floppy disk fail" and hitting F1 reboots the m […]
Show full quote

Thanks 1st of all!
Which ASUS BIOS version did you use?
The modded one complains "floppy disk fail" and hitting F1 reboots the machine.
Maybe the version you used doesn´t support the SMC chip?

Congrats about FIC HX!
I used version of ASUS 430HX with SCSI on-board P55T2P4S as a basis. Yes, this board has got Winbond SIO.
In your ASUS version there's no place for Adaptec in an IrqTable. It can be done only if to remove data about some PCI slot

AAh - the T2P4S was one of the first I tried and it crashed during startup.

The FIC AMI BIOS assigns IRQ 10 for the SCSI controller and detects it at Slot1:

majestyk wrote on 2022-11-14, 14:54:

... I used this one: […]
Show full quote

...
I used this one:

t25i0207.zip
...

I thought the ASUS BIOSes are identical about supporting both model of SIO. It appears not.
There is no space in IrqRouteTbl of this BIOS for the SCSI. So PCI slot #4 IRQ Route was removed.
Good luck!

Thanks for your help - again!
The modded ASUS BIOS still leaves onboard SCSI without IRQ. Since ASUS BIOSes are often "very special" I tried loads of alternative AWARD BIOSes in the meantime and I found one for the "NexCom Peak530" from the year 2000 that seems to be quite straightforward and uncrippled. Nearly all settings are visible by default and it has a PCI routing table with 8 lines.

Here´s the BIOS:

Modbin / AWDbedit output:

And this is what it detects on the 54TPI:

Now how do we get the Adaptec onboard SCSI device (Slot??) into this table so it gets included?

Thank you for trying the mods and not giving up 😀
I've never thought those utilities really can change irq routing. But anyway it's worth to try.
The device number of the SCSI is #8 as you see on your photos. Change 10 to 8 and that's all I think.
Also it corresponds 0x40 (hex) in IrqRouteTbl (that is on the changelogs)
(shift 8 to left 3 times)
If you don't mind I'll make another variant of IrqRouteTbl in the ASUS BIOS.
Because the last time I got all IrqRouteTbl data from the original 54TPI bios and inserted it into the bios-mod.
Now I just would like to change only the device number in original ASUS IrqRouteTbl.
Or please write your ideas how IrqRouteTbl should looks.

P.S. Did you replace a VGA ? I see the VGA the same. But it did't get any IRQ from the bios too. But it should get IRQ because there's dev num #11 in the table.
P.P.S. If after changes of dev number the SCSI gets any IRQ then you can adjust the IRQ number rotating numbers 1-4 in the row.

Yep, the ASUS BIOS assigns an IRQ for VGA, the NexCom doesn´t. The NexCom is a single board computer so maybe VGA is treated differently? It doesn´t seem to have onboard VGA.

Roman555 wrote on 2022-11-17, 16:02:

If you don't mind I'll make another variant of IrqRouteTbl in the ASUS BIOS.

How could I!
Any help /try is very welcome.

majestyk wrote on 2022-11-17, 17:43:

Yep, the ASUS BIOS assigns an IRQ for VGA, the NexCom doesn´t. The NexCom is a single board computer so maybe VGA is treated differently? It doesn´t seem to have onboard VGA.
...

IMO, a VGA is usual PCI device from IRQ point of view. Though some VGA adapters (or VGA chips) don't need IRQ at all

majestyk wrote on 2022-11-17, 17:43:

How could I!
Any help /try is very welcome.

Ok, I'll make the mentioned modded ASUS bios

P.S. One more try

Kudos to you for the effort!
Onboard SCSI still doesn´t get an IRQ, VGA does. I suspect that ASUS salted this BIOS with their own "magic" that also prevents many BIOS tools from working successfully.

SCSI and cacheable area are my main focus here, I could live with an extra ISA I/O card. I entered the first 5 lines from the original BIOS into the FIC routing table and PCI cards are identified in the right slot 1-4 now.
But onboard SCSI is ignored at the moment, because I couldn´t find a way to add additional lines for the missing two entries that take care of "slot 0" which probably is onboard SCSI.
The last line consists of zeroes only, can this one be omitted?

I also found some more AWARD files like for the Iwill P55TU that also has the 8770 SCSI chip. For whatecer reasons this and several more AWARD BIOSes that explicitly support the SMC 669 SIO don´t manage to make it work on the 54TPI.