Hard question about Quadra 650 / 800 identification

[da9000]

OK guys,

I've spent some hours trying to ID a couple of Quadra boards I have - searching all over the web. Haven't found affirmative answers yet.

Main source of information is the following (and the link at the bottom of the same page):

http://homepage.mac.com/schrier/wombat.html

The mystery:

Basically the boards are almost identical but the BIG difference is that one has a 64pin "SIMM-slot" to the left of the DRAM slots, named J24, while the other has the pins for the slot, but not the slot itself. (what is this slot for anyhow?)

Another difference: one says "WOMBAT" next to the part number (8xx-xxxx-xx, I forget right now), while the other does not. The one named Wombat is the one with the J24 slot. As an aside, they are both Wombat boards, since they are labeled with a sticker (near the LED D51) with the designation "WBT/33" or something close to that.

Both boards have R152 (on the backside) installed, but not R151. They also have 16.7Mhz crystals, and thus 32Mhz CPU clocks.

Both also have a 5pin header at J25, but no jumper.

They both show up as Getstalt 36, which is Quadra 650, but I've a hunch at least one is an 800.

Any suggestions from the experts would be appreciated!

 

[trag]

I'm pretty sure the Q650 and Q800 boards were the same, weren't they?

Also, are you certain that 16.7 MHz oscillator is for the CPU? It could be for some other circuitry. There are usually three or four on an Apple motherboard.

The 64 pin slot is a ROM socket, in case Apple ever decided to release a ROM update, which it never did. The one with the socket populated is probably an older production of the board than the one with it missing.

 

[da9000]

Hi Trag,

I'm not so sure, that's why I'm asking. These two sure look identical to me

As far as I know the 16.7Mhz is doubled to get the CPU speed (there's a chip near by that does the doubling). It's also consistent with hat I've read on various reputable sites (Mr. Schrier's for example).

Thanks for pointing out that the 64pin socket is for ROMs. It threw me off, since it was so close to the RAM sockets. Now that I think about it, it's not that far off from the SMD ROM chips either.

 

[beachycove]

The logic boards were identical in the Q650 and 800, so it sure ought to be impossible to tell them apart. At the sales counter, you'd be asked, "Do you want that on your desk, sir, or on the floor?" Depending on your consumer preferences, they'd cook up either a tower 33MHz 68040 or a desktop 33MHz 68040, and serve it up, piping hot, in your preferred location. Simple as that.

I suppose that one advantage of the Q800 form factor was that you could get an 8100 board in it (with a new backplate). The same surgery was possible on the Q650, but then you only got a 7100. 8100s were the high-end machines.

I have also found the Q800-840av/ PM8100/ PM9500 series to be admirably quiet, whereas the desktops make a fair bit more noise. It must have something to do with the power supplies and air circulation....

Some find the desktops uglier than the towers, but I rather like the form of my Q650 and IIvx. The curve on the front was one of the signature themes of Apple design right up to the time of manufacture; the air intake at the bottom of the front on the machines is especially classy: no mere grill, folks, but an elegant curve complementing the overall design. To my mind, the case design of the towers is redeemed only by the "feets" motif; otherwise, the tower design is rather unimaginative; they are also, as is well known, a pita to work on. But they were quiet machines in daily use, that has to be said.

 

[Quadraman]

The Q650 and Q700 boards are a similar form factor and the Q700 has the extra slot that you mentioned. I discovered that when building my rehoused Q700 in IIvx case. I bought an overclock kit for the 040 and it included a board that fits into the slot on the Q700 board. The Q650 does not have this slot. The upgrade kit also says it works with the Q800, so your board with the slot may also be a Q800 board.

 

[da9000]

Thanks for the replies guys! Interesting arcane knowledge

@beachycove:

Identical, except for the small differences I noted perhaps?

@Quadraman:

When you say slot, do you mean the 64pin ROM slot? If so, why would an overclocking kit need to be plugged in there!? For sucking in some juice or because it actually came with a ROM?

 

[Unknown_K]

Doesn't the Q650 have a rounded CPU heatsink while the Q800 has a square one?

 

[Quadraman]

Thanks for the replies guys! Interesting arcane knowledge
@beachycove:

Identical, except for the small differences I noted perhaps?

@Quadraman:

When you say slot, do you mean the 64pin ROM slot? If so, why would an overclocking kit need to be plugged in there!? For sucking in some juice or because it actually came with a ROM?

You need to use the ROM that comes with the chipping kit or it won't work. The kit comes with the ROM board, a couple of wires with clips at the ends that connect to the ROM board and the clock oscillator and something else I can't remember at the moment. There is also a power wire adapter to divert power from the floppy drive connector to a cooling fan for the 040. Also included is a strangely shaped card that plugs in to the Nubus slot in front of the PDS slot to power another cooling fan that attaches to the heat sink on the 601 boards. This Nubus slot is inaccessible when you have a 601 upgrade installed, so it is a good way to make use of it. I don't use the overclocking parts in mine because when I tried to install it in the IIvx case, the ROM board stood up too high and I wasn't able to seat the drive tray. I mainly wanted it for the cooling fans anyway, since my 601 card was overheating all the time.

 

[da9000]

@Unknown_K:

I don't know Mine both have square looking heatsinks. Anyone else?

@Quadraman:

Aha, so it does come with a ROM card... Interesting. Perhaps it patches the Apple ROMs or replaces them so that the overclocking will work stably?

Thanks for detailing this complicated overclocking scheme!

 

[Quadraman]

@Unknown_K:
I don't know Mine both have square looking heatsinks. Anyone else?

@Quadraman:

Aha, so it does come with a ROM card... Interesting. Perhaps it patches the Apple ROMs or replaces them so that the overclocking will work stably?

Thanks for detailing this complicated overclocking scheme!

The whole overclocking bit kinda sucks because the clips pop off too easily and it screws up whatever you're doing if the machine is turned on when the overclock stops working. It's a Newertech Power Pump, I think.

 

[trag]

Aha, so it does come with a ROM card... Interesting. Perhaps it patches the Apple ROMs or replaces them so that the overclocking will work stably?

Thanks for detailing this complicated overclocking scheme!

Did that overclocking kit let you adjust the clock speed with software?

If so, my guess is that the card in the ROM slot is not a ROM, but is using the ROM slot for access to the address and data busses.

You tell the software what speed you want. The software writes a speed code to an unused location in the Mac's address space. The message shows up on the ROM slot (as well as the rest of the address/data bus) and the card in the ROM slot decodes the message and passes it to the overclocking hardware, thus setting the speed.