Back Porting the Classic ROM to the SE

[Phipli]

20 posts and nobody has tried jamming the Classic ROMs in there yet? If I had an SE, I'd try it. Maybe you could also test it with MAME.

The Classic is a single huge chip, the SE is a High and a Low chip, that has a pinout not available as EPROM. So, an adapter is needed, plus working out how to split the ROM, plus it might not fit in the address space.

Also I was repairing the Classic.

 

[Phipli]

Just for anyone reading this, the SE ROM sockets have 17 address lines, so are 128k each for a total of 256k.

That means the Classic ROM won't fit because it is 512k. Not really a suprise since the added an OS in there.

 

[Phipli]

This said, there is ROM in the map, so perhaps if you stole an extra address line... :

 

[cheesestraws]

This said, there is ROM in the map, so perhaps if you stole an extra address line... :

The reserved space in that map is only 256k. Will the ROM actually be selected above it?

 

[Phipli]

The reserved space in that map is only 256k. Will the ROM actually be selected above it?

So reserved is 256k, but there is nothing immediately above it. My thought was you might be lucky. If the ROM base address is at the same place, and the decode logic gives echos of the SE ROM in that range, the next sequential address pin might be enough.

But, this is "prove me wrong please" logic. I'm not even at guessing level confidence. Pure hypothesis.

 

[cheesestraws]

Sounds like time to crack out macsbug and have a look. Poke just above the ROM range and see if you get a bus error.

 

[Phipli]

Sounds like time to crack out macsbug and have a look. Poke just above the ROM range and see if you get a bus error.

Yeah, or the start of ROM again. Interesting.

Heh... Might... Cough... Have to uninstall virtual.

 

[Arbee]

In MAME, the Classic is literally 3 lines:

macsefd(config); // inherit SE FDHD configuration
config.device_remove("pds"); // remove SE PDS slot
config.device_remove("sepds"); // remove SE PDS "bus"

As far as I'm aware the only real hangups on hardware are the larger ROM size (worst case you could probably run a bodge wire to the CPU to pick off the extra address line), and the .Sony driver may require a SWIM and hang if it's not an SE FDHD.

 

[Phipli]

As far as I'm aware the only real hangups on hardware are the larger ROM size (worst case you could probably run a bodge wire to the CPU to pick off the extra address line), and the .Sony driver may require a SWIM and hang if it's not an SE FDHD.

My plan was to run a wire from the CPU, they're right next door.

I believe (but haven't personally tried) that the FDHD SE ROMs happily work with the IWM. I was assuming it is the same. I think my second SE is an FDHD anyway though, and that's the one I'd mess with (rather than the SE I've had for 26 years).

Thanks for clarifying that the Classic in mame is basically running on SE hardware.

What happens if you don't remove the PDS and use the Classic ROM in MAME?

Should be fine, there isn't a slot manager or anything anyway.

 

[Arbee]

What happens if you don't remove the PDS and use the Classic ROM in MAME?

I haven't tried that specifically, but I have made Franken-configurations, usually by accident, and they normally just work. I didn't know until fairly late in the process that the Mac TV wasn't supposed to have an LC PDS slot, for instance, so I was running it with an emulated Ethernet card and connecting to my netatalk server.

 

[Phipli]

I haven't tried that specifically, but I have made Franken-configurations, usually by accident, and they normally just work. I didn't know until fairly late in the process that the Mac TV wasn't supposed to have an LC PDS slot, for instance, so I was running it with an emulated Ethernet card and connecting to my netatalk server.

Heh.

Have you ever looked inside a LaserWriter 630, it's basically and LC 3 with the standard Apple Ethernet like the COMM slot card and a weird PDS slot.

 

[Arbee]

Just for laughs I tried putting the SE slot back into the Classic and the Radius Full Page Display worked fine with the Classic ROM, as you'd expect.

As an aside, that's the only SE PDS card I have emulated right now, so if anyone has ROM dumps and PCB photos of others, I'd be happy to have them.

 

[Phipli]

As an aside, that's the only SE PDS card I have emulated right now, so if anyone has ROM dumps and PCB photos of others, I'd be happy to have them.

I'll keep it in mind, I have a video card and an ethernet card.

Off topic, but LW Pro 600 :

 

[Arbee]

Heh. 343S1035 is "Single DMA Video", kind of a V8/Sonora style system controller for LaserWriters, including the "video" interface to the print engine. Also 344S1021 is a PIC (65C02 system-on-chip), like the IIfx/Q900/Q950. That's kind of interesting.

 

[Phipli]

Heh. 343S1035 is "Single DMA Video", kind of a V8/Sonora style system controller for LaserWriters, including the "video" interface to the print engine. Also 344S1021 is a PIC (65C02 system-on-chip), like the IIfx/Q900/Q950. That's kind of interesting.

The LaserWriters are the connoisseur's Macintosh.

They really are fascinating. A later one had later model RISC CPUs from the same series as the 8•24 GC video card.

I'd love to build a video card for the PDS and swap in a video card and boot it from Mac ROMs

 

[Phipli]

Sounds like time to crack out macsbug and have a look. Poke just above the ROM range and see if you get a bus error.

Hum. Something about my accelerator is stopping MicroBug from working. Pressing the Interrupt button just gives me this :

 

[Phipli]

Ok, I can get to it if I press it after "Welcome to Macintosh" and before the accelerator's extension loads.

This is 400002A...

 

[Phipli]

... and this is 44002A... It's different. Bah. I was hoping they'd be identical!



@Arbee - are you replicating the behaviour of the SE, or the Classic BBU in the MAME SE?

@cheesestraws - am I doing something stupid?

 

[Phipli]

Ahha! @cheesestraws @Arbee! So I powered on my SE while holding the interrupt button, which is what you do to completely disable the 030 upgrade. Booted as a 68000, pressed interrupt again (doesn't crash now) and got the following - 440000 is a mirror of 400000! This means that adding the next sequential address line from the CPU should allow you to use a 512k ROM, because the ROM is enabled when reading 440000 (assuming up to just below 480000).

 

[Phipli]

@bigmessowires - ROMinator for the SE?

It's looking like it just needs a custom board to plug into the two ROM sockets, and a mini clip or soldering a wire onto an address pin on the CPU (or somewhere else that it is available.