"SAFE" LCIII and Interware Booster ROMs to support ROM Disks

[frontein1]

I recently acquired an Interware Booster for my LCIII. Of course this is the type of accelerator that does not require a CDEV/INIT driver; instead the embedded ROM on the accelerator makes runtime patches to be able to boot from the 040 via the PDS slot. These patches are made to the regular ROM image starting at 0x40800000 and after the image starting at 0x40900000.

I wanted to be able to continue supporting my custom 4MB ROM with the ROM Disk embedded. So this involved needing to make a handful of additional patches to BOTH the LCIII ROM and to the embedded ROM on the accelerator. The three main challenges I ran into were:

1. The Interware Booster itself patches the Sonora MMU tables to expand the ROM area from 1MB to 1.5MB. I bet the original developers back then probably never anticipated that someone would be competing to hack a larger ROM area. Due to how the accelerator works, these changes were taking precedence over the 4MB MMU patches in the LCIII ROM. So using a OneROM, I created what I would call ROM version 1.1.3 that adds 3MB instead of just 512KB to the MMU tables.
2. On the LCIII side, there were a couple more Sonora MMU tables I had to patch to support the 040. I didn't have to do this when I was just using the native 030. So maybe these additional tables are used by the 040.
3. I changed the start of the ROM Disk from 0x40900000 to 0x40920000. So the disk is 128KB smaller. But this is needed as the Interware Booster consumes at least 700 bytes starting at 0x40900000. I probably really didn't need a full 128KB gap, but I wanted to play it safe initially.

Here are some related posts:

1. https://68kmla.org/bb/threads/lciii-eprom.51873/
2. https://68kmla.org/bb/threads/interware-booster-40-rom-v1-1-2.52754/
3. https://68kmla.org/bb/threads/interware-booster-30-50f.38283/

I have attached three files, ready for programming:

1. LCIII LO ROM file.
2. LCIII HI ROM file.
3. Interware Booster ROM version 1.1.3.

In the next few days I'll write up a short doc that shows all the patches made to both ROMs.

 

[Nixontheknight]

and will these Hi-Lo ROMs work on a stock LC III? I might use this to swap the ROMs on my LC III

 

[frontein1]

will these Hi-Lo ROMs work on a stock LC III?

Yes should. In fact today I used this same ROM several times to boot up and use the LCIII without the Interware Booster installed. Of course, you'll need to use DIP-42 EEPROMs. I am using the extra two address pins. For this I specifically used M27C160-100. I have some faster 50ns EEPROMs but I didn't pull them out for this project.

Here is how I labeled them in my system:

 

[frontein1]

In the next few days I'll write up a short doc that shows all the patches made to both ROMs.

Here is the doc. This shows all the patches made to both the LCIII and IWB ROMs. The driver at offset 60080 is still what I call v0.90, so it does not have a splash screen. But I have been able to boot into R and RA without any issues.

If anyone gives these ROMs a try, drop a note in this thread if you have any issues so we can work them out.