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Lobos board (Strange Apple ROM)
Posted by: dougg3 on 2024-01-09 15:21:38
Oh that’s strange! I wonder which Mac would have had an 8 MB ROM during development. Maybe there is a ROM disk appended to it or something…
Posted by: Phipli on 2024-01-09 15:30:30
Oh that’s strange! I wonder which Mac would have had an 8 MB ROM during development. Maybe there is a ROM disk appended to it or something…
Given the content mentions Adobe, perhaps it is from a printer like the LW 8500 or 810?

Adobe licence PostScript which was used in laser printers.
Posted by: Phipli on 2024-01-09 15:36:56
Found this picture of part of the LW8500. It has two ROM SIMMs.

www.getthatpart.com

Apple 661-1420 LaserWriter 8500 Main I/O Network Controller Board

Apple LaserWriter 8500 Series MachinesSPARES - REPAIRS - UPGRADESGENUINE OEM Apple PartsMPN 661-1420 Main Controller BoardAlt MPN 630-2496-ANO EXCHANGE REQUIRED ! Sells elsewhere online for MUCH MORESave $$$ right here at GetThatPart ! CALL US with questions - Our business line is...
www.getthatpart.com www.getthatpart.com

1000015485.jpg
Posted by: Phipli on 2024-01-09 15:43:51
Further confirmation that it is probably a LW 8500 half ROM :

1000015489.jpg

The LW8500 has 8MB ROM in two 4MB SIMMs like this one is suspected to be.
Posted by: dougg3 on 2024-01-09 16:51:36
The LW8500 has 8MB ROM in two 4MB SIMMs like this one is suspected to be.
Ha! Nice sleuthing! That makes perfect sense with the Adobe strings and everything.
Posted by: Phipli on 2024-01-09 16:56:40
Ha! Nice sleuthing! That makes perfect sense with the Adobe strings and everything.
Grew up in an environment where there were LW 810s and 8500s about 🙂 lots of people forget they exist 😆
Posted by: Phipli on 2024-01-09 17:02:29
Look what I found in the service source 🙂

You can read the labels on the ROM PCBs almost.

1000015491.jpg
Posted by: dougg3 on 2024-01-09 17:25:34
Yep! That looks like pretty darn good evidence. I'm kind of shocked they did it this way instead of a single ROM DIMM. Maybe it was in order to fit 8 MB based on common flash sizes available at the time.

I wonder if the LaserWriter 8500 is capable of reflashing its own ROM SIMMs in system 🙂
Posted by: Phipli on 2024-01-09 17:27:22
Yep! That looks like pretty darn good evidence. I'm kind of shocked they did it this way instead of a single ROM DIMM. Maybe it was in order to fit 8 MB based on common flash sizes available at the time.

I wonder if the LaserWriter 8500 is capable of reflashing its own ROM SIMMs in system 🙂
I suspect they were using an 8100's cache slot 🤣
Posted by: Phipli on 2024-01-09 17:33:17
For interest - datasheet for ROM chips.
Posted by: dougg3 on 2024-01-10 15:22:39
Looking at those pictures in more depth, it looks like there were even provisions for two more ROM SIMM sockets for a total of 16 MB of ROM.

I find it kind of funny that the processor is an Am29040 and the flash memory for the ROM is Am29F040B. Super close part numbers. At first I was wondering if everyone involved in writing the documentation was super confused and thought the flash memory was the main CPU or something 🤣 but clearly the Am29040 is an actual CPU model by AMD. Although it seems to be 32-bit...so I'm guessing the high and low ROM SIMM banks don't actually combine to create a 64-bit data bus like I originally theorized; they probably are just activated at different times based on one of the address lines.
Posted by: Phipli on 2024-01-10 15:37:20
Looking at those pictures in more depth, it looks like there were even provisions for two more ROM SIMM sockets for a total of 16 MB of ROM.

I find it kind of funny that the processor is an Am29040 and the flash memory for the ROM is Am29F040B. Super close part numbers. At first I was wondering if everyone involved in writing the documentation was super confused and thought the flash memory was the main CPU or something 🤣 but clearly the Am29040 is an actual CPU model by AMD. Although it seems to be 32-bit...so I'm guessing the high and low ROM SIMM banks don't actually combine to create a 64-bit data bus like I originally theorized; they probably are just activated at different times based on one of the address lines.
Guessing the CPU is related to the one on Apple's 8•24 GC video card (@GRudolf94) ?
Posted by: GRudolf94 on 2024-01-10 15:41:23
Correct, an evolution of. What an 040 is to a DIP m68k.
Posted by: Phipli on 2024-01-10 15:44:00
In an alternative universe where Apple didn't want to keep Motorola on side, the Mac might have ended up powered by the AM29040. The first 68k emulator that later became the one for PPC started as an emulator on the AM29000.
Posted by: eharmon on 2024-01-10 19:45:49
Hah, a LaserWriter prototyping ROM. Given the 1995 date, I wonder if that's what they were always designed for.
Posted by: Phipli on 2024-03-15 03:16:03
View attachment 57473



I found one in my EVT Quadra 800. I would guess both are from a Q800, since the date codes on the other ROM look the same. But maybe someone else can chime in if this style of simm was re-used in other macs.
Hey @switch998 do you have a photo of the topside of your 40MHz Q800? I'd be interested what speed clock is fitted at location "G3" (next to the inner Nubus slot) and if Jumper "J29" is fitted alongside the CPU.
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