68kMLA Classic Interface

There's probably a way to extract resources from the ROM (I've never done it - maybe tbxi has a clue). The supermario InitResources code might show how to do that: RomRsrc in the ROM header is referenced using RomBase (low memory global) + 0x1A in the ReDoMap code. It points to 0x7EC10. Each resource seems to point to earlier in the ROM for the next resource.

         - Starting with the 512k ROMs (Classic, Classic II, LC, LCII,
           IIci, IIsi, IIfx), there is still an offset at offset $1a,
           but the format of the data is different.
           - This is possibly the first generation of "32-bit clean"
             ROMs.
           - $1a points to a structure of unknown length ($0a bytes?)
             that starts with an offset... to what might be a ROM heap
             arena for a resource header?  Seems to be a $30-byte
             structure, at least.
             - 8 bytes into that target is a link to the next such
               maybe-arena (or zeros, at the end of the list).
             - $0c bytes into the target appears to be the offset of
               some resource data.
             - $10 is the resource type (four bytes),
             - $14 is the resource ID (two bytes),
             - $16 is unknown (one byte), maybe resource flags?
             - $17 is the count byte for the resource name string (up
               to twelve characters),
             - $24 is unknown (four bytes)
             - $28 seems as though it might be related to the resource
               data length somehow, but not directly?
               - Seems like the length, rounded up to a multiple of
                 sixteen ($10) bytes, with a minimum value of $10 for
                 zero-length resources (the FONT resources that are
                 used to store font names, in particular).
                 - KCHR 0 in the Quadra 950 ROM appears to have this
                   value $10 higher than the actual length of data.
                 - This might be an attempt at the usual "add one less
                   than the allocation granularity, then mask off the
                   low bits to the granularity", except missing the
                   "one less" part.  The end result would be that
                   everything that isn't already aligned gets rounded
                   up, and everything that /is/ aligned gets bumped to
                   the next boundary anyway.
               - The practical upshot here is that it seems unlikely
                 to be able to easily get accurate length information
                 for ROM resources.
             - $2c is unknown (four bytes), seems to increase by 8
               each subsequent entry in the list?

Updated my dumpromresources script at https://68kmla.org/bb/index.php?threads/pict-data-format.49561/post-557931

# Automated dump of Macintosh ROM resources

# The (optional) combo mask switches a resource based on the DefaultRSRCs
# field of the box's ProductInfo structure. (The low-memory variable at
# 0xDD8 points to ProductInfo, and the DefaultRSRCs byte is at offset
# 0x16.) The combo field is usually used for the Standard Apple Numeric
# Environment (SANE) PACKs 4 and 5.

# Summary of known combos:
# 0b01111000    AllCombos (DEFAULT)         Universal resource          
# 0b01000000    AppleTalk1                  Appletalk 1.0               
# 0b00100000    AppleTalk2                  Appletalk 2.0               
# 0b00110000    AppleTalk2_NetBoot_FPU      Has FPU and remote booting  
# 0b00001000    AppleTalk2_NetBoot_NoFPU    Has remote booting, no FPU  
# 0b00010000    NetBoot                     Has remote booting

type=PACK   id=4        name=Main               src=Rsrc/PACK_4_AT2_NetBoot_FPU     combo=AppleTalk2_NetBoot_FPU
type=PACK   id=5        name=Main               src=Rsrc/PACK_5_AT2_NetBoot_FPU     combo=AppleTalk2_NetBoot_FPU
type=PACK   id=4        name=Main               src=Rsrc/PACK_4_AT2_NetBoot_NoFPU   combo=AppleTalk2_NetBoot_NoFPU
type=PACK   id=5        name=Main               src=Rsrc/PACK_5_AT2_NetBoot_NoFPU   combo=AppleTalk2_NetBoot_NoFPU
type=PACK   id=7        name=Main               src=Rsrc/PACK_7
type=PACK   id=8        name=AevtMgr            src=Rsrc/PACK_8_AevtMgr

Thank you! I just downloaded that repository, so I'll take a look at all this. Seems like a ton of good information in there.

The little project I am working on is building my own variant of the netBOOT driver from scratch.

ROM Resource Reference Entry @00051c80
    ComboBits             "00011"
    offsetToNext          0x000edc70
    offsetToData          0x00051cb0
    rsrcType              'DRVR'
    rsrcID                49
    rsrcAttr              0x58
    rsrcName              ".netBOOT"
    memHeader             0x00051ca4
    memTag                0xc0
    memSize               2164
    memMaster             0x00000304

combos 1 to 4 # 0b01111000    AllCombos (DEFAULT)         Universal resource          
combo 1       # 0b01000000    AppleTalk1                  Appletalk 1.0              
combo 2       # 0b00100000    AppleTalk2                  Appletalk 2.0              
combo 2 and 3 # 0b00110000    AppleTalk2_NetBoot_FPU      Has FPU and remote booting  
combo 3       # 0b00010000    NetBoot                     Has remote booting
combo 4       # 0b00001000    AppleTalk2_NetBoot_NoFPU    Has remote booting, no FPU

#define AppleTalk1                  0x40            /*  Appletalk 1.0               01000000 */
#define AppleTalk2                  0x20            /*  Appletalk 2.0               00100000 */
#define AppleTalk2_NetBoot_FPU      0x30            /*  Has FPU and remote booting  00110000 */
#define AppleTalk2_NetBoot_NoFPU    0x08            /*  Has remote booting, no FPU  00001000 */
#define NetBoot                     0x10            /*  Has remote booting          00010000 */
#define AllCombos                   0x78            /*  Universal resource          01111000 */