IIfx ROM SIMM in a IIsi . . .

[Trash80toHP_Mini]

. . . has anyone already tested this configuration as yet? :?:

My research aim is to discover whether the OO Pseudo Slot Macintosh Video Address, which is unimplemented in the IIfx, will disable the Vampire Video Sub-System in the IIsi.

This would be a VERY GOOD THING!!!!!!!!!!! }

 

[Trash80toHP_Mini]

Well, I finally decided to try my IIfx ROM SIMM in the IIsi despite the lack of confirmationthat it has been done successfully or unsuccessfully already, without damage to the IIfx ROM SIMM or the IIsi.

I got no boot chimes from the IIsi, but the IIfx booted just fine after that little experiment!

Phew! NO OOPSIE! [] ]'> [)] ]'>

edit: I finally remembered where I'd seen the reason that this won't work . . .

. . . AFTER I did the experiment! :

From the Another IIci ROM hack thread:

But until then, is anybody interested in boards? I'd be happy to send out bare boards to anyone for $2.90 (1/12 of my PCB order cost) plus the cost of shipping Like I said, the SIMM should work in any of the II series Macs that have a ROM SIMM socket with the exception of the IIsi but that can be fixed by cutting a trace, and also the SE/30.

Food for thought! HRMMMMMM . . . }

 

[tt]

Odd, the IIfx and IIsi ROM SIMMs work in an SE/30, so you would think a IIfx ROM would work in a IIsi.

 

[Trash80toHP_Mini]

Backward compatibility for ROM cleanliness on the SE/30 is one thing.

However, forward compatibility for increased utility of the IIsi is an entirely different animal!

_______________________________________________________________________________________

I'm waiting to hear which line needs to be cut on the dougg3's IIci ROM SIMM to make it work in the IIsi.

_______________________________________________________________________________________

I'm betting that Apple didn't want either the IIfx or the IIci ROM SIMMs to be compatible with the IIsi!

IMHO, the IIsi was intentionally hobbled as a Low End or, at best, a Mid Market Mac:

__Its RAM config was limited to an odd number by soldering 1MB as Bank A directly onto the Mobo.

____The 4 SIMM Slots available for Bank A on the High End Macs IIci and IIfx being excised from the IIsi to "protect" High End $ale$$$$$$!

__Its expansion was limited to an either/or PDS/NuBus choice physically and probably electronically by, ever so slight, changes to the SE/30's PDS.

____This was probably aided by barring implementation of the NuBus signal on PDS Cards for the IIsi, that pin's signal being different on the SE/30.

__Its ROM/Memory Mapping was limited to only FOUR NuBus Slot/Pseudo Slot Addresses. :disapprove:

Thus, the intentional borking of the IIsi's ROM SIMM pinout!

These changes effectively barred its MoBo from being used for an eminently expandable Hackintosh.

 

[tt]

However, forward compatibility for increased utility of the IIsi is an entirely different animal!

I see, I always thought (incorrectly) the IIfx was the last II model. 8-o

 

[dougg3]

Hey jt,

I'll go ahead and reply in here. The difference I noticed was on the SIMM pin 46 (left to right, with the notch side on the left). GttMFH2E says it is +5 volts, but the IIsi's dev note says it is A23 (GttMFH2E only goes up to A22, which is on pin 45). I really don't know if Apple actually connected that pin on the IIfx SIMM -- you'll have to check it. I'm assuming that hooking A23 to VCC would be a bad thing. The simple solution to make my new custom SIMMs compatible with both is to leave pin 46 not connected to anything. On my SIMM design, I had it connected to all the other +5V pins on the SIMM. I should have probably just left it unconnected. So if Apple connected that pin to anything on the IIfx SIMM, that could be causing your problem.

More likely though is that the IIsi's just too new for the IIfx's ROM code I wonder if the reverse would work? (IIsi ROM in a IIfx)

 

[Trash80toHP_Mini]

THX, comrade! I'm way too tired to go through GttMFH2E tonight.

I'll probably scan and print the entire memory sections for the IIfx and the IIci and then print the same section from the IIsi DevNote so I can three-hole punch the lot for inclusion in my "Hacks Binder" when I get a chance.

I'll have to check out the release dates of all three machines.

I'm sure the IIfx ROM is based upon the IIci ROM because Mac II Video shows up in the SlotInfo Reports and the IIfx AIN'T GOT NO VIDEO! The IIsi has been described by at least one member as: "a IIci with a microphone input."

We'll see, but I'm fairly convinced that the IIfx ROM SIMM ought to boot the IIsi . . .

. . . with a MUCH more flexible memory mapping scheme! :approve:

. . . or not! :-/

 

[dougg3]

Interesting...I'm kind of curious now to try IIfx and IIsi ROMs in my IIci after you mentioned that. I have the hardware necessary to try it now!

Any updates? Did you check to see if that pin was hooked to VCC on the IIfx ROM SIMM?

 

[dougg3]

Naturally after asking that question, I tried to boot my IIci with a IIfx ROM and a IIsi ROM using my programmable ROM SIMM.

It worked fine both times! Not sure if it really has any benefit, but it does work. In both cases, About this Macintosh in System 7.0.1 still identifies the computer as a Macintosh IIci.

 

[IPalindromeI]

Did you have a NuBus video card installed? If so, Trash80 was curious as this might disable the onboard video that noms system RAM.

 

[dougg3]

No video card installed, I was using the onboard video and it still worked...

 

[bigmessowires]

In both cases, About this Macintosh in System 7.0.1 still identifies the computer as a Macintosh IIci.

That's curious. How does it know?

 

[Trash80toHP_Mini]

Cool! What I'm trying to do is to open up more NuBus and Pseudo Slot memory blocks in the artificially limited IIsi memory map.

I'd like to use the DuoDock's Gemini Card to get a second (7 inch) NuBus Card into the Box underneath the Full Length Rocket 33 . . .

. . . as well as the Radius Color Pivot II PDS Card and PDS NIC going underneath the MoBo at the same time! }

I don't think disabling the MoBo's Vampire Video poses any problem at all, the System Polls the Video sense lines for PixelCount & Color Depth on startup and doesn't seem to buffer any of Bank A's Memory if no monitor is hooked up to the port (or set up in the PRAM?) so hacking a FULL Bank A shouldn't be problematic.

 

[dougg3]

That's curious. How does it know?

Not a clue! There must be something else it can do at runtime to identify which model it's running on. That might be an interesting section of code to disassemble.

I wonder if it will still identify as an SE/30 when put in an SE/30?

Cool! What I'm trying to do is to open up more NuBus and Pseudo Slot memory blocks in the artificially limited IIsi memory map.I'd like to use the DuoDock's Gemini Card to get a second (7 inch) NuBus Card into the Box underneath the Full Length Rocket 33 . . .

. . . as well as the Radius Color Pivot II PDS Card and PDS NIC going underneath the MoBo at the same time! }

Ooh, tricky! So you're trying to open up the ability to use more than 1 NuBus slot? I hope it works!

The only thing that kind of troubles me is that the only successful combinations I've seen so far are newer ROMs running on older hardware, but the IIsi is newer than the IIfx. I sure hope the IIfx ROM in IIsi idea works though!

 

[Trash80toHP_Mini]

If the IIfx ROM doesn't work, maybe the IIci ROM will, dunno.

I don't have the IIfx Docs handy, does it have an audio port in like the IIsi?

 

[dougg3]

I'm pretty sure the IIsi was the first in the II series to have built-in audio input. (Maybe the first Mac ever to have it?) The IIfx doesn't have an audio in port...

 

[Trash80toHP_Mini]

I'm fairly certain the IIfx ROMs won't work in the IIsi, but I'll be testing that again soon!

The IIfx is a really strange dead-end branch of the Mac Block Diagram Tree! 8-o

I think I'll be trying a IIci ROM SIMM in the IIsi at the earliest opportunity. Two NuBus Slots and one PDS Slot will fill my needs nicely with a couple of good breaks.

Gotta find my Video/NIC card next. :approve:

 

[Trash80toHP_Mini]

No joy in Mudville!

As suspected, the modified IIfx ROM SIMM didn't boot the IIsi, but it STILL boots the IIfx! Go figure! :

I've got a IIci ROM SIMM to test somewhere in the mails ATM, so round 2 should be soon. I found out that the IIfx ROM SIMM boots a IIci. I'll test the IIci SIMM in the IIfx while I'm at it, just for kicks.

Ah well, here we go again. }

< hopes to avoid disassembly of this ROM series just to tweak the IIsi' s memory mapping. |) >

 

[Trash80toHP_Mini]

Better news today! :approve:

One of our intrepid ROM Hackers PM'd me about the possibility of a jumper on the motherboard that might be necessary to reset to toggle MoBo ROM & SIMM ROM, so I checked it out and found one to try! I stuck a header pin jumper on it and it disabled the MoBo ROMs all right! [] ]'>

Tried the modified IIfx ROM SIMM again on my lunch break, but no joy . . .

. . . tried the stock IIfx ROM SIMM and I got boot chimes! :

The Radius Color Pivot II PDS Card's Pre-boot splash screen followed up a four chime (?) memory error message, (?) which didn't really surprise me a bit.

Wolfed down some lunch and went back to work with GttMFH2E in hand and did a bit of copying and research. The error message probably results from the 1MB soldered to the IIsi MoBo as a funky Vampire Video RAM Buffer. It appears that the IIfx can't use SIMMs smaller than 1MB, so the IIsi's measly equivalent of four 256k SIMMs in Bank A made the IIfx ROM SIMM equipped IIsi barf!

Got home after work just now, pulled all the RAM out of Bank A of the IIfx and it booted up just fine! :approve:

Next step: desolder all the VCC connections to that measley 1MB of soldered DRAM on the IIsi's MoBo and see what transpires! }