On Mon, Oct 3, 2011 at 9:41 AM, Jeff Walther <[email protected]> wrote:
> > Actually, heavy wire will make things worse. It's likely to have more > capacitance and inductance which will create impedance for the > signals. Your best bet is 110 fine gauge twisted pairs, with each > extra wire being a ground wire. This would be a nightmare to > connect, but it's probably doable. > > Thicker wire has lower resistance to DC signals, but digital signals > are high frequency AC signals, not DC signals. For AC signals, > Impedance (basically resistance) is proportional to capacitance and > inductance , so you want to keep those two as low as possible in > higher frequency connections. > Hats off to you, you just saved me a lot of work. What you say makes sense, and explains something I saw on 68kmla. A member (can't remember his name) had rigged lots of cards into an SE/30 using chained DIN connectors for interconnects, stacked like legos. The accelerators weren't working so well. All the pins and springs inside those chained connectors would add a lot of surface area, which would increase capacitance and mess with the signals. So, given this new information, the (modified) plan is to use shielded narrow gauge wire with as few socket connections as possible between the accelerator and CPU socket. > I could have sworn that Artmix was hawking them on Ebay within the > past year. Still expensive, but ultimately, cheaper (but not as much > fun) as building your own. > Negative. I've been watching eBay like a hawk for over a year. No sightings. > You want the IIcx adapter. The IIx adapter has a PLD on board. > > <http://www.prismnet.com/~trag/MacIIxAdapter.jpg> > > I do have a IIcx adapter in the attic, but it's packed in the least > accessible reaches up there, and I won't be getting it down any time > soon. If I do I'll trace out the connections. It's a good idea, in > any case, to document the connections on these old Daystar adapters. > > I think that Bunsen on 68kmla has one, but he's in Australia. > Good to know. I'm guessing the PLD has something to do with that CPU pass-through socket. Why would they do this for the IIX but not for other macs? If you get around to tracing the connections, do pass the word. A mysterious case of your favorite libation would find its way to your doorstep. On Mon, Oct 3, 2011 at 10:37 AM, TT <[email protected]> wrote: > > What Jeff said also reminded me of when I made a cable harnesses and used > 20AWG instead of 22AWG. It makes a big difference when you have a bunch of > wires together. Having 100+ would be a pain to route through the chassis. > Maybe a flexible circuit or ribbon cables to connect from the socketed > adapter to the DayStar accelerator would be easier to manage. > > Yeah, he saved my bacon. To address the cable clutter problem, I'm going to make a crude representation of the cable's path out of lumber and screw hooks. Then I'll cut, size, and solder each cable into it, then wrap the bundle in electrical tape. Given Jeff's info, it seems prudent to limit my use of extra connectors and keep the wires as direct as possible. It should retain its shape when removed from the jig and make fitting it into the SE/30 easy. -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
