Date: Tue, 30 Sep 2003 06:29:04 -0500 From: Derek Morton <[EMAIL PROTECTED]>
As I mentioned, the order of bus scanning is important to note. If you have devices with the same ID on both the internal bus and the external bus, the device on the internal bus takes precedence.
Okay. I wasn't sure that's the way it would work, because on some Macs, a SCSI ID conflict will cause a freeze at boot up. But perhaps, that's only true for a hardware ID conflict on the same physical bus and not a problem for ID conflicts on logical busses.
Thus you only have access to 7 devices until 4.3 loads... Or so the theory (and documentation) goes. I should have time to do some testing this weekend.
I have never heard anything about 4.3 being in a JackHammer card, but I would suspect it would only be in effect for the card, and would not effect the built in internal / external bus problem. I will be sure to remove my JackHammer before I begin testing, i will also try it with the card to see if there seems to be any effect.
I look forward to hearing the results.
I have purchased most of the parts I need to make a new PDS card (for maximum Zoom!)
What are you going to put on the PDS card? This sounds very cool. Hmmm. I'm going to guess 68060 processor? That would also explain the custom ROM code you mention further down.
and a replacement ROM card, but I have not (yet) figured out the ROM slot pin out.
The ROM SIMM has the same form factor as the SE/30, Mac II ROM SIMM for which the pinout is available from resources on the LEM Compact.Macs list. Of course, it may not have exactly the same pinout. The easiest way to figure the pinout if you can't get actual documentation is to trace the connectivity of the ROM socket pins to the pins of the ROM chips using an ohmmeter with an audio indicator (saves looking over at the display).
I have here a Q700 MB, but no Q900 nor Q950 MB. Assuming that the Q700 uses the same ROM chips and SIMM as the Q900, I have the pinout for the ROM chips and can email it to you if you need it. It's just like an Atmel AT49F8192 with pins 1, 2, 44, and 43 sawn off. The chips on this board are Toshiba TC534200 ROMs programmed for Apple. Once you have the ROM chip pinout, determining the ROM SIMM pinout should be simple.
The only trick is disabling the on-board ROM when you install a ROM SIMM. On the IIci there's a jumper to do this. On later machines, and I think this includes the Quadras as I see no jumper, they use a clever trick.
One of the pins in the ROM socket connects to the _CE pins of the motherboard ROM chips. The _CE pins of the ROM chips are tied to GND weakly (about 300 - 500 ohms). When building a ROM SIMM, simply connect that pin directly to the 5V supply. This will pull the _CE pins high, disabling the ROM chips on the motherboard. _CE is active low, so pulling it high disables the chips. Pin 11 in the Q700 socket connects to the _CE on the motherboard ROM chips.
Naturally, for the chips actually on the ROM SIMM, you will tie _CE to GND so they will be active when the motherboard chips are disabled.
What are you using for a replacement ROM card? The IIfx, IIsi and SE/30 ROMs I've seen use chip packages which just aren't readily available any more, so substituting one of them in wouldn't work very well. It would be too difficult to find chips to program with your new code which will easily fit on those boards.
Having a board made is certainly a possibility, especially because a two layer board would be adequate. However, the board needed is .050" thick and all the deals on cheap custom PCBs are .062" thick.
Given the above, I'm very curious what you are using for a ROM board.
Another possibility would be to just replace the ROM chips on the motherboard. If you can find a 2 Mb Flash or EEPROM chip in the standard 40 pin SOP package it would work. It might be possible to use the 8 Mb Flash in the 44 SOP or PSOP, but I'm not sure if the 44 SOP is just a bit longer than the 40 pin, or if it simply has a tighter pin pitch.
Okay, I just checked. The 44 pin SOP has the same pin pitch as the 40 pin, so it might be doable, but the 44 pin is wider, so the pins would be out at the outer edges of the solder pads for the 40 pin.
My thought is to replace the standard SCSI manager in ROM with 4.3.x (whatever the final version was)...
Do you know how to do this? If so, how did you learn? Are you an experienced Mac programmer? Good at reading disassembled 680x0 code? What? How? This is the kind of thing I'd like to know how to do, but have little idea where to start. I have basic skills in C and machine language (6809, TI DSP) but just don't know how to open up a ROM and play with the stuff inside.
I also need to include some custom code to accommodate some of the hardware changes I have already put in place
My curiosity is piqued! What have you done? Or are you waiting until it's finished to reveal?
(and wasn't there a memory bug issue... or was that just with A/UX?).
I haven't heard of it, but that doesn't mean much.
Jeff Walther
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