Thread

Help! Attempting SE/30 cpu socket to PowerCache pinout

Help! Attempting SE/30 cpu socket to PowerCache pinout 68k 39 posts Oct 17, 2011 — Dec 18, 2011

#31 Thu, 20 Oct 2011 - 05:21

I probed the pins in red, and it seems like they aren't connected to the pins at the cache slot.

I probed the resistors:

R1: 678 ohms

R2: 390 ohms

R3: 678 ohms

The pins below are ones I happened to find first, and then I started poking other ones that seem related.

R1: F11 short and other pins labeled +5, F12 390 ohms

R2: L6 short and other pins labeled +5

R3: L6 short and other pins labeled +5

There's also a C3 and a C9 underneath the male-to-male socket adapter. I used the Daystar PGA puller to get that part off.

C3: H3 & GND

C9: F2 & GND

I don't really understand what should be connected to what for resistors and capacitors, like should the resistors be in series with links between the cache and cpu sockets? Maybe a hypothetical schematic would help me understand how to probe it more efficiently.

#32 Thu, 20 Oct 2011 - 22:01

Hmm, I don't quite get it either. An x-ray would be pretty useful right now. Can you verify F12? I think I should have made that one yellow instead of green.

#33 Fri, 21 Oct 2011 - 10:38

If it's to be a straight wiring deal, you might need cable drivers at the CPU end

N00B question: what's a cable driver?

How many PseudoSlots are already accessible on the SE/30 anyway? :?:

Consult gamba's SE/30 corner, or the Minitower SE/30 site. One or t'other of those pages has that info, I believe.

the Artmix Adapter's PAL / you shouldn't need it at all [for] SE/30 or IIsi cards

Well ... no. As the above two sites demonstrate. It's strictly for the IIci-PDS Daystar accelerators.

So are the PDS pass-through slots in series?

They're not physical slots, they're pseudo-slot addresses. And the cards themselves select their address (as I recall), not the Mac, nor any adapter. Most cards are hardwired to one address (or ID), some can be reset with jumpers. The physical arrangement of cards matters not a whit, except insofar as which cards have a passthrough PDS, and physical space issues.

#34 Fri, 21 Oct 2011 - 10:44

http://www.biwa.ne.jp/~shamada/fullmac/se30_minitowerEng.html#pds_adapter

2. How to install three cards to a single PDS slot?
The important criteria are

(1)whether the card has a pass-through slot to install an additional card; and

(2)whether the slot address of the card is configurable with a jumper switch.

#35 Sun, 11 Dec 2011 - 19:13

I've managed to get my hands on a IICX adapter, and have completed the pinout page. In theory, this diagram could be used to wire up an adapter between Daystar accelerators and any 68030 socket.

http://hiddenkingdom.net/temp/pinout.htm

My only remaining question is this: the card has 8 small capacitors arranged in parallel. All of them bridge +5VDC and GND. This puzzles me. Can anyone with some EE experience explain this? Why use 8 small caps rather than 1 large cap?

Now to build one and see if it works...

#36 Tue, 13 Dec 2011 - 17:19

They sound like decoupling capacitors.

#37 Fri, 16 Dec 2011 - 19:22

My only remaining question is this: the card has 8 small capacitors arranged in parallel. All of them bridge +5VDC and GND. This puzzles me. Can anyone with some EE experience explain this? Why use 8 small caps rather than 1 large cap?

In general, smaller capacity capacitors (lower farads) react more quickly. So, let's say your supply is 5V and you can't tolerate a low voltage condition which lasts for more than 10 ns. So you need a capacitor with a small enough rating that it can react and supply stored charge to bring the voltage back up in less than 10 ns.

However, you may need to supply 30 watts of power at 5V = 6 amps. So you need enough capacitors that they can supply 6 amps at the difference in voltage which might occur. So you use a bunch of them, until they have enough charge capacity to supply 6 amps.

But these little caps are going to be depleted really quickly. They may react quickly, but they don't store much total charge. They may react within 10 ns and be exhausted by 50 ns. So if you want to be able to bridge a shortfall which lasts 1 millisecond, you might put in a much larger (in u Farads) capacitor.

This capacitor will react more slowly, but that's okay, the little guys have it covered during the initial period. By the time the little guys are out of spare juice, the big guy has started supplying current and is now supporting the voltage and being a (relatively) big capacitor, it can last much longer than the little guys.

In practice, there will be a bunch of little chip ceramic capacitors in the 1,000 - 100,000 picofarad (1 - 100 nanofarad) range (at least on newer faster stuff), some electrolytic or tantalum caps in the 10 - 50 uF range, and a few bigger guys in the 200 - 500 uF range.

In practice, I doubt that the adapter board really needs the caps. There are decoupling caps on the logic board around the CPU socket. There are decoupling caps on the Daystar upgrade board. It seems unlikely that they're really essential on the adapter board as well, but Daystar put a lot of engineering into their stuff. They may have added a little overcapacity.

#38 Sat, 17 Dec 2011 - 21:22

I've managed to get my hands on a IICX adapter, and have completed the pinout page.

Great work IamSpartaus, I'm glad you found a board. Thanks for sharing the pinout. Looking forward to seeing the end result. Are you making a PCB/harness for the adapter?

#39 Sun, 18 Dec 2011 - 02:35

Trag- that's plausible. I'm going to experiment with variable numbers of caps to see if it makes a difference. I'll be using a Turbo040, so if anything has power requirements enough for this to matter, that's it.

tt- the project is happening, but on hold due to obligatory holiday vacationing. It's going to be mostly wires, with a small pcb to unify the 5V and GND wires, and to hold any caps I'll use. Expect progress in january