Jump to content

Booting Mac Plus right from ROM + some games!


Recommended Posts

http://www.synack.net/~bbraun/plusrom/index.html

( Rob's Post on his site )

 

The Mac Plus (and associated machines) have 1MB of contiguous address space around the ROM, starting at $400000 through $4FFFFF. However, the Plus ROM is only 128K in size. This project is for an adapter to allow a full 1MB ROM plugged into the Mac Plus, and a modified ROM image to utilize the extra space as a ROM disk.

 

 

Just got mine from Rob, and really makes the PLUS cool. Boots up instant. Works Great!

- just pop old rom's out

- pop new unit in

- solder the 2 wires from rom to A18 and A19 legs of the cpu

and your all set!

 

If anyone wants to buy a Mac Plus system, with this mod already installed...

talk to bbraun.  He is desperately trying to get rid of a whole fleet of his Mac Plus machines.

I'm sure his prices are quite fair!

 

My ROM has - Mac OS 6.0.8 installed and some Games as well! 

 

post-1852-0-40057500-1415422483_thumb.png

post-1852-0-82573900-1415422531_thumb.png

post-1852-0-54309400-1415422569_thumb.png

post-1852-0-57706100-1415422612_thumb.png

post-1852-0-57817700-1415422642_thumb.png

post-1852-0-00019900-1415422842_thumb.png

 

 

heck, this rom with an older OS might even work with the Mac 128k

This one here should also work with the 512k.

 

post-1852-0-57807300-1415423853_thumb.png

Edited by uniserver
Link to post
Share on other sites
  • Replies 77
  • Created
  • Last Reply

Top Posters In This Topic

http://www.synack.net/~bbraun/plusrom/index.html

( Rob's Post on his site )

 

 

Just got mine from Rob, and really makes the PLUS cool. Boots up instant. Works Great!

- just pop old rom's out

- pop new unit in

- solder the 2 wires from rom to A18 and A19 legs of the cpu

and your all set!

 

If anyone wants to buy a Mac Plus system, with this mod already installed...

talk to bbraun.  He is desperately trying to get rid of a whole fleet of his Mac Plus machines.

I'm sure his prices are quite fair!

 

My ROM has - Mac OS 6.0.8 installed and some Games as well! 

 

attachicon.gifScreen Shot 2014-11-07 at 11.47.44 PM.png

attachicon.gifScreen Shot 2014-11-07 at 11.48.34 PM.png

attachicon.gifScreen Shot 2014-11-07 at 11.50.05 PM.png

attachicon.gifScreen Shot 2014-11-07 at 11.50.35 PM.png

attachicon.gifScreen Shot 2014-11-07 at 11.51.38 PM.png

attachicon.gifScreen Shot 2014-11-07 at 11.53.23 PM.png

 

 

heck, this rom with an older OS might even work with the Mac 128k

This one here should also work with the 512k.

 

attachicon.gifScreen Shot 2014-11-08 at 12.16.22 AM.png

 

This is what I was talking about a couple of months ago! (Only to be told that it's not doable or a waste of time.)

Link to post
Share on other sites

he has a solution for that too

http://www.synack.net/~bbraun/mackbd/index.html

 

use standard ps/2 mouse / keyboard

with 128k/512k/plus annnnnnnnnnnnnnd now supports adb as well.

combopcb1.jpg

 

How does that board fit into the Mac? Without cutting into the case, I mean.

 

With a relay in the right spot, one can plug in the device and the board would automatically set it for which set up it is without needing a jumper.

BTW - I was converting old serial mice to Mac back in the 1990s, so that wiring scheme works great if one had an adaptor!

Edited by Elfen
Link to post
Share on other sites

 

Which converter, Techknight - the Mouse one or the ROM One?
 
With the Mouse one, I'm just saying from what I know that one can wire up a relay to ports and when you insert a mouse/kb to it, it would set the relay to that port and the Mac would see it. No need to manually set jumpers as I see on this configuration.
 
- - - - -
 
I like to share information, Uniserver. If somebody is doing a project, within reason I like to share information on what I know. Months ago I asked if the ROM SIMM doable for a Mac Plus or SE, and gave an explanation on how it could bee done, stated exactly that the ROM Space is 1 or more MEGS but the ROM itself is less than 256K, making it possible to put in a bootable system in there like on the Mac Classic. I was told flatly that it is not possible without an entire rewrite of the ROMs and other stated facts that I did not accept.
 
Excuse the RANT here...
 
Years before the first Macs came out of the assembly line, I was writing video games and programs which required rewriting ROM Routines of various systems of the time, this includes cartridge systems which redo the systems' ROMs. This taught me long ago that computers are more flexible in their ability to do various tasks. All it requires is a little work, work that I have done before and fully understand.
 
Right now I do not have the equipment, but I do have the knowledge. And I'm willing to share that with anyone interested in it.
 
Now, my current idea is adding more RAM to an Old Mac and give it some use somehow. In seeing the memory maps, I have to disagree that the 6522 and other VIAs on the Mac board takes up 1 MEG of memory space when these same exact same chips were on 8bit machines before the Mac and they only took up 1K or less of physical space! 1KB, compared to 1MB is a big difference. So this creates holes in the memory map that can be filled with RAM and have that RAM used by the system as something. Perhaps a RAM Disk without taking up System RAM. This would also require a small system patch or program for its own self standing application. There is about 8MB of free space floating about in the memory map that can be used just for that on the Mac 128K - SE as it is; 4X as much on the Mac II series. All it takes is a little brain power to figure it out, even on paper as a theory. Not to tell others that its not doable or it requires a massive rewrite of the system.
 
Ideas are great, but they are worthless if no one tests them, even on paper. It if fails at that point (like my last idea on Classic II by doubling its Bus) then its fine with me. Like on the idea with the Classic II, the problem was with hardware deliberately crippling the idea and the system to be 16bit and not its true 32bit, making the idea impossible to do.
 
But this Plus Boot ROM is a great idea, and it looks like somebody stole that idea. I will say that looks can be deceiving. However, months ago I made the post of doing a Bootable ROM for the 128K - SE like on the Classic and was told that it is not possible without at least a complete system rewrite that knowledgeable people would not want to do. But here is a post of the exact idea mentioned being done. If somebody would have told me long ago that such an idea is in the work by somebody, I would have been very happy with these results. Thing is, I'm not happy with how it happened though I congratulate bbraun on getting it done. In the least he made an idea come true.

 

https://68kmla.org/forums/index.php?/topic/22324-dougg3-rom-simm-list-of-machines-that-its-electrically-compatible-with/?p=239950

Dougg3,

 

Would it be possible to do a set of ROMs for the 512Ke/Plus to load up System 6.07 like on the Classics? What would take to get this accomplished?

 

 

 

https://68kmla.org/forums/index.php?/topic/22324-dougg3-rom-simm-list-of-machines-that-its-electrically-compatible-with/?p=240000

 

I doubt they can address enough ROM space to make it possible. However, my knowledge on this subject is quite limited, so, someone feel free to prove me wrong.

 
 
https://68kmla.org/forums/index.php?/topic/22324-dougg3-rom-simm-list-of-machines-that-its-electrically-compatible-with/?p=240094

According to Guide to the Macintosh Family Hardware, the 128k/512k/Plus have a reserved ROM space of $100000 bytes in size (from $400000 to $500000). That's 1 MB. The logic on these old systems is probably dumb enough that if you wired up all the address lines, you could technically make use of all that address space. It's probably technically possible, but I don't know how many of the necessary address lines are actually brought out to the ROM sockets. I'm too lazy to figure it out right now  :)

 

Keep in mind that even if it's technically possible with hardware, it takes a software hacking genius like bbraun to make it do something. I hope everyone understands that all I did was design the hardware and hack the startup sound. bbraun did all the really cool software stuff with it.

 
 
Again, I congratulate bbraun on getting it done. The thing that I am feeling is being burnt by this. Almost like a newly elected senator going to congress and finding out that things are not going to get done unless it is in clandestine missions where I join specific circles with secret handshakes, wear funny hats and have moneys passed under the table.
 
End of Rant.
Edited by Elfen
Link to post
Share on other sites

I'm not seeing the issue here, they were already working on something, a long time before you even broached the idea, and they accomplished it. End of story.

 

Hell. I'm hoping BBraun can adapt this for the Classic II and its weird ROM expansion slot. That would give nearly 3.5 megs of ROM space. I coudl fit a small System 7 install on that.

Edited by Paralel
Link to post
Share on other sites

I have to agree with Uniserver about the post I'm quoting a fragment of below. Not cool, dude. Everyone goes through the experience now and then of feeling like someone "stole my idea!", but... seriously, you're basing this on posting a question that was itself phrased as "What would take to get this accomplished?" in a thread about someone else actually doing the legwork to get the idea working on related hardware? Seems to me that if you *had* lifted a finger to do this yourself first, which clearly you didn't, BBraun and Dougg would have excellent grounds for b****ing about you "stealing" *their* idea.

 

(Not that I think it's particularly likely they would have objected unless you did something egregious like stolen their code without giving them credit.)

 

If you'd really wanted to participate in building this I suspect they would have let you in if you'd showed more interest in the idea than a single forum post. Did you even try?

 

Now, my current idea is adding more RAM to an Old Mac and give it some use somehow. In seeing the memory maps, I have to disagree that the 6522 and other VIAs on the Mac board takes up 1 MEG of memory space when these same exact same chips were on 8bit machines before the Mac and they only took up 1K or less of physical space! 1KB, compared to 1MB is a big difference...

 

Stupid question: Do you actually fully understand how address bus decoding works? I'll be short here: A single VIA, if fully decoded, would only occupy 16 bytes of address space, so, yes, you could fit thousands of them into 4MB. However, *MANY* cheap computers, and the Mac very much falls into this category, don't fully decode their address buses, in order to save on logic. Instead they'll carve out a bigger block of memory, call it "I/O" space, and simply cram some peripherals in there in such a way that address lines are used directly as chip selects. Think about it: you have a 24 bit address bus. (Okay, technically the 68000 has a 23 bit bus and an even/odd byte line, but it's effectively the same.) That means to fully decode an arbitrary 16 byte (4 bit) space you need 20 gates. If instead of doing that you say "eh, forget that, I'm swimming in address space so I'll just decode the four address lines and use the fifth for the chip select" you'll get exactly what you get in the the Mac, which is one little chip chewing up half a megabyte of address space. Strictly speaking the VIA is still only using 16 addresses, but those addresses are going to be repeated 2^15 times through that block. To share that space with RAM you'd have to:

 

A: Add decoding hardware to the Mac's motherboard to decode the other, what did I say, 15 address lines you didn't bother with? (I'd have to look at the schematic again to completely refresh my memory.) If you don't then the VIA (Or IWM, or SCC, or whatever) is going to be enabled at the same time the RAM is, and:

 

B: Bear in mind that although *hopefully* any software that addresses the VIA will only use the 16 contiguous addresses starting at the base of the big smeary block it resides in to talk to it, it's very possible that ill-behaved software that for some reason takes advantage of the address duplication may exist.

 

Seriously, this is why half the Mac Plus' address space is occupied by peripherals that should really only consume a few hundred bytes of real address space. I'm a little mystified myself sometimes why Apple designed it to be *this* sloppy, when they could have added something like a single 74LS154 to the board to provide some chip selects for peripherals inside a smaller space. (They were already using PALs anyway, one more PAL and they could have easily fit ROM and peripherals into, say, the top 4MB leaving 12MB for RAM.) But that's how it is, and that means that a plan to add more than 4MB of RAM to a 128k through Plus would have to do some serious remedial work on the motherboard. (Or, at least, hang an alternate memory system off the CPU socket that includes the additional decoding in front of the motherboard, which would essentially be treated like a "peripheral".)

 

Page 10 of this book has a good explanation as to why one VIA and two PIOs take up 2k of address space in a Commodore PET instead of 24 bytes. The Mac is this on steroids.

Edited by Gorgonops
Link to post
Share on other sites
  • 3 weeks later...

ok super cool, just got my second rom kit from rob, and its working great just like the other one.

So now both of my Pluses are booting from ROM!  My Test Machine and my Collection machine.

 

So i tried this rom in a 512k, and bad news, The Adaptor does not line up right.

its about 3-4 MM too narrow,  So looks like rob might have to redesign a PCB for the 128k and 512k machines.

 

This in conjunction with the Floppy EMU is pretty RAD, and i almost never use that word,  (RAD) lol 

Link to post
Share on other sites

Too narrow - like it doesn't fit in the 512K's motherboard's ROM sockets? Or there's a clearance problem, and something is bumping into something else?

 

I was looking at this too. With one extra connection to the CPU, I think it would be possible to make the Flash ROM reprogrammable from within a running system. So then you could alter the contents of the ROM disk, or do other experiments, without having to open up the Mac and pull the chips back out. I've got some parts on order to build one of these, then I'll try this to see if I can make it work.

Link to post
Share on other sites

Too narrow - like it doesn't fit in the 512K's motherboard's ROM sockets? Or there's a clearance problem, and something is bumping into something else?

 

I was looking at this too. With one extra connection to the CPU, I think it would be possible to make the Flash ROM reprogrammable from within a running system. So then you could alter the contents of the ROM disk, or do other experiments, without having to open up the Mac and pull the chips back out. I've got some parts on order to build one of these, then I'll try this to see if I can make it work.

 

The one thing that bothers me with hot flashing, you would have to shadow the ROM, no? because if I am not mistaken, there are constant calls in and out of ROM. you would almost need to disable ALL interrupts and calls during the flash, which means video would go bye bye. 

 

I would imagine if you write or re-arrange code while that block is running might cause a freeze/hang and poof done. 

 

any thoughts? 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...