From: "Dave Park"
The only aspect of the QXT-640 I dealt with was that all the cards had the 7805 regulators removed and links inserted as the boards were given a clean 5v supply. It was a trap and bane of my existence that I had to carefully check any card I worked on to see if it had been adapted for a QXT-640 - inserting it in a regular QL would instantly destroy it.
Not instantly ;-). I once have built a similar Desktop QL, long before the arrival of the QXT. I unfortunately threw it away (whithout cards) and my cards also did not have a 5V regulator because of one big power supply for all. When I got a QL years later from Urs, I insertet the QFlash EPROM card (with PE and additional software on it) and it worked a few minutes, then the QL freezes. I instantly remind myself about the missing regulators.
I recall the order of cards was important, but not what order, or why it was important - though anyone who has ever designed a backplane knows the importance of buffering and signal integrity ;) *winks*
I had just an bus expansion card (6 slots) with no buffering nor capacitors with 20cm flat cable to the QL's bus and all worked, nevertheless which order the cards had. I also had an additional connector to insert a QEP III from outside half inside the case and it also worked without problems. Of course I took care, that the SQB inside and the QFlash Eprom card inside don't use the same addresses, so that I could insert the QEP III and use it.
BTW: If one wants to use one microdrive with such a self-made system, putting a germanium diode in the select cable of the microdrive let you select the microdrive as mdv1_ *and* mdv2_. I have done that and to my surprise it worked.
Cheers...Ralf
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