Writing new ROMs for Apple Mac LC - Page 1
Forum section: electronics / general

author: dexters_lab
author_rank: Unknown
timestamp: December 27, 2018, 08:32:24 pm
content: i have a couple of old Apple Mac LC systems on the way, not working and they are missing the original ROMs for some reason so i'll either need to source some or preferably burn some replacements to i can get them back up and running.From what i can see the 512kb image is spread over 4 ROMs, does anyone know what EPROMs i need to buy to write the image on? 27C128? something more exotic?

author: Halcyon
author_rank: Unknown
timestamp: December 27, 2018, 11:21:57 pm
content: I have a bunch of working Apple gear. Let me know the model number of the unit and I'll see what's installed and image some ROMs for you if you wish.

author: dexters_lab
author_rank: Unknown
timestamp: December 28, 2018, 01:30:11 pm
content: thanks, dont suppose you know what eprom part will drop in place of the mask roms?i am utterly new to this apple stuff!

author: stevelup
author_rank: Regular Contributor
timestamp: December 28, 2018, 10:43:46 pm
content: I believe 27C010. Image needs splitting in half, then interleaving.So you end up with LL and LH which is the first 256K and HL and HH which is the second 256K. The sockets are labelled as such (or certainly were on mine).No longer have it though, so can’t really help further..

author: ebastler
author_rank: Super Contributor
timestamp: December 29, 2018, 08:26:33 am
content: The ROM dumps are available online, of course.E.g. here:https://www.macintoshrepository.org/7038-all-macintosh-roms-68k-ppc-512k total for the Mac LC seems right, in four 128k chips.Instead of buying new EPROMs, you might also consider getting these:https://www.ebay.com/itm/Macintosh-LC-ROM-Chips-IC-4-Chip-Set-341-0392-0393-0394-0395-Vintage-Apple-/131678144990

author: dexters_lab
author_rank: Unknown
timestamp: December 30, 2018, 09:05:00 am
content: awesome, thanks!

author: technix
author_rank: Super Contributor
timestamp: January 02, 2019, 07:20:22 am
content: The 68020 can support Linux. So if you dont want to use propertiary code from Apple (and sacrifice Mac OS support) you can build a new one using u-boot as the basis. Linux can run on that 68020.

author: dexters_lab
author_rank: Unknown
timestamp: January 02, 2019, 09:23:14 am
content: Quote from: technix on January 02, 2019, 07:20:22 aminteresting idea... the owner wants to restore them as Macs, but i'll certainly mention it, they have two of them so maybe they might want to convert one to linux.

author: technix
author_rank: Super Contributor
timestamp: January 02, 2019, 07:42:33 pm
content: Quote from: dexters_lab on January 02, 2019, 09:23:14 amThere is a chance you might be able to make u-boot and Macintosh Toolbox to coexist in the ROM, this way you get to multiboot.For u-boot and Macintosh Toolbox to coexist, the Toolbox routines that Mac OS depend on has to be included as-is, while the startup code can be replaced with u-boot SPL, compressed u-boot proper and a compressed custom Mac OS loader.

author: cdev
author_rank: Super Contributor
timestamp: January 02, 2019, 07:47:59 pm
content: I think Apple basically gave those old ROMs to Archive.org to host. I may be wrong on that but I vaguely remember seeing them - I think there and reading something to that effect.I really enjoyed OS 7, 8 and 9. All sorts of fun stuff existed on that platform that never made the jump to OSX.But it was soooo crash prone, I don't miss that.

author: fchk
author_rank: Frequent Contributor
timestamp: January 05, 2019, 05:48:25 pm
content: Quote from: technix on January 02, 2019, 07:20:22 amA full Linux instance always needs a MMU - either the 68851 for standard 68020 systems, the proprietary SUN MMU for 68k Sun workstations, or the MMU built into the 68030/40/60 (but not the 68EC*** versions!).There is uCLinux fore MMU-less systems like PalmPilot, but it is limited.

author: technix
author_rank: Super Contributor
timestamp: January 05, 2019, 09:26:06 pm
content: Quote from: fchk on January 05, 2019, 05:48:25 pmLinux mainline since somewhere in version 4.x has uClinux patches mainlined, so MMU with latest mainline is no longer a hard requirement.Also a Macintosh LC can have 68030 or 68040 based accelerator card installed, which will allow it to run full Linux with MMU too.

author: ebastler
author_rank: Super Contributor
timestamp: January 05, 2019, 09:31:08 pm
content: Quote from: technix on January 05, 2019, 09:26:06 pmThat is a weasel response. What you meant to reply tofchkis:"Ah, yes, I got that mixed up. A 68020 as present in the Mac LC is not enough to run full-blown Linux. Thank you for catching that."

author: technix
author_rank: Super Contributor
timestamp: January 06, 2019, 08:33:13 am
content: Quote from: ebastler on January 05, 2019, 09:31:08 pmWell I still stand by my statement, since I am coming from the perspective of running latest mainline Linux. Since the 4.x code merge there is no longer distinction between regular Linux and uClinux, hence the more appropriate way of saying is this:Without the accelerator card you will have to compile the MMU out. However if you have an accelerator card you need a kernel that has MMU compiled in. Either way you should go with a recent 4.x kernel.

author: barbeque
author_rank: Contributor
timestamp: March 05, 2019, 04:22:17 am
content: The ROM-inator II was also recently available, but the 5V flash chips that it used were discontinued, so no more are being made:https://www.bigmessowires.com/mac-rom-inator-ii/Schematics and details are also there.Handy if you want to add a "little extra" to the ROM without the hassle of burning another chip.I hadn't heard before that they merged the MMC-less patches to Linux; I'll have to give that a try on one of my '020s. I used the (very limited) MacMinix for awhile, but that ran under the Mac side anyway.