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LaserWriter 810 Pro ROM

Dandu

Well-known member
I search a specific things, can you help me ?

I search a ROM dump from the LaserWriter 810 Pro. Actually, i have found many pages with reference to an easter egg with this printer, and i will verify that... and i must find the ROM. I have not found a printer to make the dump.

My article about that : https://www.journaldulapin.com/2019/04/20/pizza-burrito-imprimante/ (in french)

There is information about that on this pages : http://www.mackido.com/EasterEggs/LaserWriters.html https://news.ycombinator.com/item?id=13439752 https://en.everybodywiki.com/Stump_the_Experts

 

NJRoadfan

Well-known member
I can't imagine Apple sold too many of these. Whatever was in service was likely scrapped at this point.

 

dougg3

Well-known member
Ahh, good call on the checksums. I didn't even realize they were checksums. These files look really weird to me. I tried interleaving them myself, but I don't see anything close to human readable. I would have expected some Apple copyright text in there or something. I guess there doesn't have to be human-readable text, but it seems like there would be something that binwalk would recognize.

binwalk seems to think that the entire file (until you get to the part with all FF) has a pretty constant entropy around 0.6. I'm not sure what that means...

Is it possible that they've remapped data pins and/or address pins a little bit in order to "encrypt" the contents? It would be interesting to trace the pins back to where they go on the microcontroller or processor or whatever is in control.
 

cheesestraws

Well-known member
I had a brief look earlier trying to get a copyright notice out with a couple of unorthodox bit orders (reversed bits, reversed nybbles) but I couldn't see one. Though I couldn't test interleaving, mostly because I ran out of time.
 

Dandu

Well-known member
Actually, there is two other chip with "data/rom" on the sticker, but i can't dump it now : the chip is not the same and my adapter cannot dump it.

And dougg3, for the checksum, the first time, i have not seen that. But when i have made a second dump to be sure, i have seen the value and "tilt" : it's the same value !

I will try to dump the two other chip with a friend.

And it'w very complicated to try to understand the code : it's not a 68000 based printer like the first LaserWriter, it's a Weitek 8200, a RISC CPU (PA RISC, i mean, but i'm not sure)
 

Dandu

Well-known member
A friend dump the two others chip for me and... YES ! http://down.dandu.be/ROMcostena.bin

It was true : there is an easter egg about burrito on the ROM ! (there is many text string about the restaurant, the burrito, etc.)

Next step : i will try to extract the text (i suppose it's a postcript text, but i'm not sure) ti see the original page
 

chi100

Member
It looks ROMcostena.bin is the ROM of the Ethernet board and not the printer mainboard. What CPU does the Ethernet board use?
 

chi100

Member
Or actually maybe those aren't the ROMs of Ethernet board. I see two other ROM looking things in a picture. Can you post a picture of the ROMs that you dumped?
 

chi100

Member
I took a closer look at the situation. The Weitek 8200 is a Harvard architecture so the code and data live in different address spaces. This means the 4 ROMs you posted first are the code and the second ROM is probably the data.

There's a rough disassembler here: https://github.com/jrmuizel/weitek-8200-disasm/ that seems to work on the code ROMs.
 

Dandu

Well-known member
Hi

Thank you !

It's note the ROM from Ethernet board (i have dumped the ROM too). I have annoted a photo.

s-l1600.jpg
 
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