Color Classic earlier ROM swap?

8 replies [Last post]
Offline
Joined: Mar 12 2005
Posts: 117

Is it possible to use an earlier 256k or 512k ROM in a CC? I'm guessing the ROM is what determines whether the CC can run System 6 or not. When I insert a 6.0.8 disk it starts to load, then I get the "can't use" message. If an SE30, IIx, cx, ci, si or fx ROM (all 68030 system 6 & 7, color machines) were compatible with the CC socket, then theoretically I could run system 6 under the old ROM, though I might not have access to all of the CCs features. Any ideas? Where would I find info on the ROM chip specs to know which one might fit? Anybody have any of the aboev machines to check? Thanks.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
tmtomh's picture
Offline
Joined: Dec 20 2003
Posts: 568
Give it up

A Color Classic is not going to "become" a Mac 128 or 512 or Plus - either by putting one of those machines' motherboard into it, or by trying to somehow swap ROM chips. It's not possible.

Matt

Offline
Joined: Mar 12 2005
Posts: 117
New Approach

Well anything is possible ... this new approach is simply to enable the CC to run System 6 (not System 1.0), so I can use it as a disk formatting transition computer to my 128/512k. If i have to have another Compact around I would want it to be a Color Classic!

I've done some pretty bizarre hacks to Color Classics so I'm up for the challenge. Though a ROM swap is a pretty minor thing -- if it works.

eeun's picture
Offline
Joined: Dec 19 2003
Posts: 1891
Re: New Approach

Mac128 wrote:

Well anything is possible ...

No, it's not. What a 128/512 ROM works with is the -rest- of a 128/512. It will not be able to work with a CC motherboard, even if it was pin compatible.

Also, it is not just the ROM which determines which operating system a Mac can run. The OS has to possess the code to recognize and use the rest of the hardware.

But by all means, try it if you must.

Quote:

so I can use it as a disk formatting transition computer to my 128/512k.

If you want a more 'modern' compact Mac to run 6.0.8, get an SE/30.

__________________

"Give a man a fire, he's warm for a day. Set a man on fire and he's warm for the rest of his life."
(Terry Pratchett)

Offline
Joined: Mar 12 2005
Posts: 117
WHat A ROM Does

Yes I know. BUT, here's a perfect example: The Mac Classic is identical in virtually every respect to the Mac Plus. There is ONE BIG difference: the Classic can only run System 6.0.7 (even though it has a version of 6.0.3 built-into its ROM). Why? There is obviously an artificial limitation being imposed on the Classic for some reason. Maybe it was a marketing effort to force customers to use System 7 on which Apple's future depended. I don't know. Here's another example: SYstem 6.0.8L -- a special system hack Apple did not widely promote which allowed the Classic II, LC II and PowerBook 100 to run on System 6 -- ALL required System 7 otherwise. Just because a particular Mac has particular features doesn't mean the software or CPU has to use them. The old Mac 128/512k to Plus upgrades are a perfect example: The 64k/128k ROMs could be interchanged. Put a 64k ROM in a Plus board and you lost support for some of the Pluses features, but it still worked. I doubt there is a compatible System 6 ROM that will fit in the CC's sockets, so I have to start looking at software hacks that will allow me to trick the CC into running System 6. I've no doubt I could put an earlier motherboard in there altogether, but it would also require substantial time and effort and the payoff just isn't worth it. Most likely I will stick a MacMini in there and run any of several 68k emulators to span the entire Apple OS history and related software. The quest for System 6 on these early System 7 Macs is not a new one -- System 7 was so bloated with thick code and extra features that the early 68030 processors that were underclocked ran like molasses compared to System 6 -- I'm sure the reason for Apple's 6.0.8L hack. I, like many others believe that this System limitation is an artificial barrier and that while System 7 might only support certain features on a certain machine, System 6 should work just as well with the loss of those features.

tmtomh's picture
Offline
Joined: Dec 20 2003
Posts: 568
What a ROM Does - and Doesn't Do

The reason that one can swap 128 and 512 and Plus ROMs is that the motherboards are based on the same design (in most respects). Once you move to the CC you've not only got onboard SCSI, you've also got a different CPU, a 32-bit-clean machine (versus 24-bit), a different system bus, different expansion ports, different speed ports, different hardware components (including, most likely, a different SCSI controller from the Plus), and a different memory controller, among other things. Please, go ahead and try it if you want. But don't try to persuade us that it will work, in the absence of actually trying it yourself.

One interesting thing, though, would be to try to take the ROM from an LCII and put it into a CC. The CC and LCII are based on the same mobo design, and AFAIK the only difference is that the CC mobo uses the edge connector while the LCII mobo uses standard internal ribbon and wire connectors (and the external monitor port of course). So, since the LCII will run System 6 (via 6.0.8L), a ROM swap there might actually work.

The only other way to get a Mac to run an earlier, unsupported version of the Mac OS would be to write your own System Enabler - which would probably be tough given that Apple doesn't publish any documentation on its enablers (AFAIK). And even then, the success would depend on having very similar mobos (ie. CC and LCII).

As for the Classic and the Plus, they both use 68000 CPUs, but they're not identical from the low-level hardware-software interaction standpoint of a ROM. The Classic requires 6.0.7 not because of Apple marketing trying to force people to upgrade, but rather because 6.0.7 no doubt adds some code that's required to support the Classic - prior versions of System 6 came out before the Classic did.

Now, Apple could've gone back and added the necessary system hacks to System 6.0.2 or something like that - but System 6 was free, so what would be the point? System 6.0.7 was an improvement over previous versions of System 6. Conversely, the Plus could run 6.0.7 - so the Plus was in no way made obsolete by the release of 6.0.7.

As for 6.0.8L, AFAIK it exists for the same reason System 7.1.2PPC exists, and for the same reason OS8.1 for iMac G3 exists - they're all hacked versions of the Mac OS used for a short period of time on the first shipments of certain Mac models - in other words, the next version of Mac OS wasn't quite ready when these units first came off the assembly line. BTW, the Color Classic is often mistakenly included in the list of Macs that will run System 6.0.8L - is that perhaps where this current quest to run System 6 on a CC began?

Matt

Offline
Joined: Mar 12 2005
Posts: 117
Right

You're right ... there are aspects of speed and chip specs which are relatively transparent to the casual techy that I overlooked. I never intended to stick a 68000 ROM in the CC, but I was thinking along the lines of the LCII as you suggest (which IS included on the 6.0.8L) list as well as the Classic II and others I listed in my original post. I find it interesting that the CC has socketed ROM chips rather than permanently soldered chips on the other 5xx boards that will fit in the CC. As for custom enablers, I think a software hack is all that's required -- the CC is a case in point: there are folks who have figured out how to hack both system and enabler files to force the CC to use 640x480 resolution without any of the complicated hardware hacks. If this is possible, so are others, but like you say -- how does one begin to decode them -- i.e. remove the restrictions to running 6.0.8 and simultaneously disable and CC features that might conflict with 6.0.8.

I completely understand what you are saying about the commonalities between the 68000 128/512 & Plus re: ability to use ROMs. But I'll add another one to that as well: the 68000 SE to 68030 SE30. The ROM chips are swappable. Then again they are virtually identical except for processor speed. And I doubt the SE ROM would handle the SE30 PDS slot correctly. Following your LCII logic, the SE30 could work too as it is basically a Mac IIx, which is basically an LCII. Not trying to convince you guys ... just working it through for myself. Another interesting note: the Classic has a ROM that is two pins short of filling the ROM slot it ships in.

tmtomh's picture
Offline
Joined: Dec 20 2003
Posts: 568
Re: Right

Mac128 wrote:

I never intended to stick a 68000 ROM in the CC, but I was thinking along the lines of the LCII as you suggest.

That would be cool if it worked - I hope you or someone else will try it, because you've really piqued my curiosity!

Mac128 wrote:

I find it interesting that the CC has socketed ROM chips rather than permanently soldered chips on the other 5xx boards that will fit in the CC.

This is something I've often wondred about - do all CCs have socketed ROMs, or only the earlier production runs? I know the CC mobo changed during production, but I can't remember if the ROM-socket aspect was among the changes or not. Stuart? Anyone?

Mac128 wrote:

As for custom enablers, I think a software hack is all that's required -- the CC is a case in point: there are folks who have figured out how to hack both system and enabler files to force the CC to use 640x480 resolution without any of the complicated hardware hacks.

No. You can hack the System file (using 7.5.x, 7.6.x, 8.0, 8.1) or the System Enabler (using 7.1) in order to allow a 575-upgraded CC to work properly with the CC's original 512x384 resolution. But to get 640x480 you've got to modify the hardware.

Mac128 wrote:

I completely understand what you are saying about the commonalities between the 68000 128/512 & Plus re: ability to use ROMs. But I'll add another one to that as well: the 68000 SE to 68030 SE30. The ROM chips are swappable. Then again they are virtually identical except for processor speed. And I doubt the SE ROM would handle the SE30 PDS slot correctly. Following your LCII logic, the SE30 could work too as it is basically a Mac IIx, which is basically an LCII.

The SE/30 has a much different RAM setup than the SE, among other things. If an SE/30 with an SE ROM really will boot up and run, that's very interesting. I wouldn't have expected that to be the case.

As for an SE/30 basically being a IIx, as a matter of fact an SE/30 will in fact work fine with the ROM SIMM from a IIfx or a IIsi.

But I don't think it's accurate to say a IIx is basically an LCII. One good indication of how different they are is that the former will run A/UX while the latter won't - because A/UX bypasses the Macintosh Toolbox and accesses hardware directly. This means that the LCII's hardware is different from the IIx's in some significant way (I'm thinking video, expansion slots and memory controller, for starters).

Best,
Matt

Offline
Joined: Mar 12 2005
Posts: 117
Attempt

Planning on giving it a try ... thought for sure I read a software only hack that allowed the 640x480, but you're probably right. I think I mispoke about the SE & SE/30 -- I think I was talking about the Superdrive ROM swap on the SE FDHD upgrade, both of course 68000 Macs. BUT, I just got a Mac Plus 1MB which had a MicroMac 68030 upgrade card on it. I was shocked as that card basically only adds a 68030 chip to the Plus and the original Plus ROMs are still driving it, for the most part. I'm sure there are some ICs on the baord that redirect some of the ROM instructions into the 68030, but WOW! Interesting about the LC II & IIx, could it be the lak of a math co-processor in the LC, or is it really a major hardware difference? Thanks for the insight.