I'm not sure I want to get into a pricing discussion again at this time, as I tend to be too optimistic about things. I think we're sitting pretty good at the moment though, with about $10 in parts and another $7-8 for the PCB.
Hi Hargle! Thanks! Your sunny optimism makes me happy. However part of my job as "Cmdr Buzzkill" is to reign in unrealistic expectations with generous application of buckets of cold water.
I believe it to be too early to discuss final unit price as well. While working on the updated PCB layout last night I noticed that there have been *many* changes to the production unit compared to the prototype. I've lost exact count but its more than ten changes for sure. Since we've barely begun initial testing and already racked up so many changes it may be prudent to consider another round of PCB prototypes before making the big order. Probably after we've strained out the really big bugs with the initial round of testing the second round could be broader and go for more depth and variety.
Why another round? I am very concerned about parts interference and with all the changes to the PCB outline pushing the boundaries outward that eventually we are going to hit something. I've done some measurements and I *believe* we had about 1mm clearance on the right hand side of the PCB before it contacted the bracket. That 1mm clearance is now gone to allow the Keystone 9202 brackets to actually contact some PCB material. Some independent confirmation would be good so that we get PCBs that really fit in the target computer. That there don't appear to be any defined standards for the outline of an ISA PCB makes this is all sort of hit or miss.
The bracket skirt issues make me worry too. What are the physical tolerances of the 62 pin edge connector? Is there enough clearance between the edge and skirt? How would we know? The original design was extremely conservative and basically trimmed off all the interference danger zones. I can see why now and it was a wise approach. The semi random layout of an XT/AT motherboard is a witches brew of pieces and parts strewn all over. Who knows what sort of crap is going to get in the way? I have no idea.
On top of that, just for fun, I tried an early initial respin of the PCB just to see what the effect of all the changes are on the trace routing. Well, I can tell you it ain't pretty. The default router could not make a solution in ~45 passes and that's not good. I manually interceded and did the last few trace by hand. When the optimizer started there were 195 vias and >429 inches of overall trace length. In other words, the PCB looks like a plate of spaghetti (traces) with a half a bottle of parmesan cheese on it (vias). Its going to take some serious time to get the optimizer to straighten the mess out and even then is going to be more complex than the initial prototypes. I started the optimizer yesterday evening and when I checked it this morning (0530) it was almost 50% complete *on the first pass*. Ugh.
There are some costs like the initial prototype PCB costs that need to be recouped, but that'll only add an extra couple bucks per order if we do 100 of them, which is what I was planning on doing. If you assemble it yourself, I think you will easily get away with paying less than $40 total. (I still wanna say about $25-30). If you're going to make me assemble it, then you're going to pay for my soldering and testing time, which at the moment, is not worth it!
~1994, or whenever drives went bigger than 528MB.
I *strongly* suggest using drives no more than 10 years old, since things have standardized a lot in that time frame, both electrically and software spec wise.
Agree. $40-$50 is probably the reasonable zone, IMO. IDE hard drives that are LBA and <10 years old is certainly reasonable device support.
You are certainly entitled to recoup your expenses and then some. You've already shown more patience, fortitude, and persistence than most. Good on you.
Thanks and have a nice day!
Andrew Lynch
PS, BTW, I also checked the hdtest run on the XT test station. Its up to 0018xxxx of 00FBxxxx sectors. Does this need to go all the way to the end or can it be aborted part way through and still provide meaningful results? If it were encountering errors would it have printed them already or do I wait until its done? I hope the power stays up for the next two weeks!
