dougg3 wrote:Would you mind looking at my +5V traces after I change the copper fill?
Or are there more complicated rules about how they are supposed to be connected?
Never use power planes. It is not needed, as dc-supply currents only need small traces. A power plane may resonate with the groundplane: your PCB will act as dipole antenna!
ojfd wrote:When there are only two layers availble I usually route +VCC as traces, dedicate one side to GND and connect all large copper islands on the other side to GND with several vias evenly spread around that copper island. That's when working with clock rates up to 25 MHz.
trag wrote:JT, the interrupt for each slot has support in hardware. So even though all the ROMs for both three and six slot models may have code to poll six slots when an interrupt occurs, the interrupt signal line(s) from the slot need to be connected properly.
I don't know how the 68030 models handle the hardware end -- I think it involves the VIA registers -- but in the PowerMac x500 models, the Grand Central chip has a pin for each interrupt and the interrupt wire from each PCI slot must be connected to a unique interrupt pin on Grand Central. Since the PCI slot IDs are coded into the ROM/Open Firmware Device Tree in those models, I suspect that the interrupt used needs to match the PCI slot address.
Anyway, the point is, that expanding the number of slots supported goes beyond providing support in the ROM and hooking up the expansion bus. The interrupt line connection can be pretty complicated.
ojfd wrote:One good idea is to separate ICs by using ferrite beads in their VCC lines and capacitors to GND after them. As bonus you gain space underneath those beads to route traces there, in cace where they will otherwise cross. I also don't see any larger (10uF +) filtering caps on your board. At least one would be good to buffer VCC that's coming from USB. SMD or 'thru hole', whatewer works.
ojfd wrote:Never use power planes. It is not needed, as dc-supply currents only need small traces. A power plane may resonate with the groundplane: your PCB will act as dipole antenna!
I knew, it was something like that, nice to have it confirmed by someone else. But as I said before, it might work OK on your board, so don't worry too much about it
bigmessowires wrote:I wish there were some kind of "PCB layout for Dummies" to learn from. I've been adding bypass capacitors, and trying to minimize trace lengths, but otherwise it's all just seat of the pants engineering. Fortunately everything I've designed so far has worked.
dougg3 wrote:Is this OK/advisable to do, or am I creating some kind of crazy antenna or RF emitting? Or does
it not matter at all?
dougg3 wrote:I have a headache now, but 400+ DRC errors fixed later, I now have a board that passes the test with 8 mil spacing...
I think I'm going to pass on the ferrite beads on this board, but I'll definitely keep them in mind in the future (or if I start having hardware problems...)
...sorry if these PCB design updates are getting annoying, I'm almost done!
ojfd wrote:Congratulations, dougg3, very nice job! Fixing 400+ errors manually indeed takes some time.
ojfd wrote:I thin'k it's very good and very educational to that you're publishing progress of your design, especially for casual reader.
Trash80toHP_Mini wrote:I'll second that motion
Trash80toHP_Mini wrote:I've got pictures of triangular adapter cards dancing around in my head!
** silly literary reference for anybody who's read to kids
Trash80toHP_Mini wrote:If there's any way to move the USB connector over so that it hangs over the edge just about the thickness of a piece of thin plexi (actual thickness to be determined) and the DB-9 out to just about the same amount, I can see your board enclosed in a clear box with a clear plexi hinged lid or a rabbeted pop-top!
ojfd, what do you think?
ojfd wrote:Otherwise, you know what they say about the camel? It is a horse designed by the committee.
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