Martyn Hill, Esq. wrote:One thought - those 2mil pitch headers are more awkward to find connecting cables for than the more common 2.54mil pitch - could it work to include the 2mil (to connect to the Q68) and a 2.54mil for the pass-through connector?
Derek_Stewart wrote:Hi Dave,
Nice PCB, but a couple things I do not like.
Front mounting Network sockets. The Front will look very cluttered, I would prefer these on the left hsnd side (looking from the front).
New hole for the power switch, there are two Aluminium guide rails to drill through, which there is a risk of drill jamming.
I am fitting male 2x12 DIL Pin Headers.
Can not agree to this unofficial standard, you use discuss a proposed standard before trying to force it through.
The net sockets can not fit to the sides. They have to mount slightly beyond flush with the metal surface. Side mounted, it would become impossible to slide the Q68 board into the existing cases as the jacks have a fixed and rigid relationship to the PCB, whereas the power switch does not because it is on a flying lead. You suggest putting the net sockets to the sides, but then in the same breath suggest it would be too hard to put the power socket on the sides because it is hard to drill. The power socket embeds quite nicely into the outside upper slot, just by sanding the top and bottom edges of its lip off.
The front may look cluttered, but unfortunately the back is fully occupied. Since there is a power cord in the front, it made sense to have other similar sized cables as close to it as possible. I tried to put the second net port over
the power socket, but there isn't clearance. This is the trade-off with Peter's incredibly compact and efficient design. I am probably going to have to shave the left edge of the board very accurately, so it tucks in very flush against the power socket. I did consider trying to use a pair of corded sockets, but then the sockets are not switched and termination would not work correctly. I might even have to move R2 and R3 up behind the jacks to make the board slimmer. I know I am good on the supercap side but on the power jack side it is *very* tight.
I'm speccing the female header to be on the Q68 because it's the correct choice for this application. The address and data lines are directly linked to the FPGA and RAM. The FPGA has clamping diodes on most pins, but the RAM does not. The pluggable connector supplies power so it would be less than ideal because clearances require unshrouded pins.
The experts wrote:Electronic designers often select female jack connectors for fixed mounting on electronic equipment they design. This is usually done because female connectors are more resistant to damage or contamination, by virtue of their concealed or recessed electrical contacts. A damaged motherboard connector can result in the scrapping of an expensive piece of electronic equipment. The risk of expensive damage is reduced by relegating the more exposed male contacts to connecting cables, which can be repaired or replaced at lower cost.
I will supply both headers loose, so if someone opens their Q68 and finds a male header they will be able to proceed. It's a soldering required job anyway. That way, they can do what they want.
Follow-up to this is a floppy interface. It uses the same IC used on the SGC, so drivers already exist in SMSQ/E. They just need the target address and spacing of registers editing. I've done the hardware, but the driver is beyond my skills.
Again, much appreciation to Martyn Hill for his excellent work with this driver.