I’ve been successfully running dbmail for about 10 years now, but all my clients are using POP3, which seems a bit more stable. We have occasional issues (primarily that if disk space usage gets to over 50% mysql stops being able to compact tables after deleting messages, which ends up accelerating disk usage even more until the system runs out of space … and mysql’s behaviour when it runs out of disk space leaves a little to be desired).

]]>“I found that max speed of 7400 ttl logic series is about 25mhz” Using 74Sxxx and 74Fxxx parts ought to be able to cope with the speed required quite easily. Most of the logic would be perfectly fine even with 74LSxxx devices, but counters could be a bit tricky — e.g. the 74LS293 counter can count at 32MHz, but is only 4 bits wide… to extend it out to the 10 bits required for the hsync counter here will slow it down because you’ll need 3 of them in a chain, and waiting for all 3 to settle after a clock pulse will typically require 3*34 + 10 = 112ns, so about 9MHz is the most you could hope for. The 74F269 however would work: to start with it’s 8 bits wide, so you’d only need two of them, and has a 9-10ns response time, so you could have two of them running together at 50MHz if you wanted.

Much more problematic is that over about 10-15MHz you start to have to worry a lot more about your PCB design (e.g. having traces that are roughly equal length for signals that need to arrive at the same time), which is of course harder the more complex your circuit gets. GALs therefore look *very* tempting to me too. 🙂

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