Originally posted by: Peter
VirtualLarry, the K7S5A's well-known disliking of marginal PSUs and RAM isn't so much about engineering margins.
Sure it is. Proper noise-filtration/"smoothing" circuitry costs extra money, both on the mobo and in the PSU. If you leave them off of both, then you're going to have problems. (Unfortunately an all-too-common scenario though, with customers looking to pay as little as possible for components.)
I'm not all that happy that mu current MSI KT4V-L board only has a two-phase VRM for the CPU power either, and is missing a lot of filtering/reserve-power caps between the PCI slots, even though the board layout has spaces for them. :| So I guess I'm not saying that ECS or PCChips is the *only* company in this biz to cut costs/cut corners with components, they all do, to some extent or another.
Originally posted by: Peter
On the PSU front, we must keep in mind it's an old design that doesn't yet use the separate 12V plug for the CPU power circuitry. Hence, it needs a PSU that is adequately strong on the 5V rail ... which happens to be where most of the cheap PSUs skimp.
Considering how many similar system of the time ran fine on those same wattage PSUs in different boards, I can't quite agree that the problem was simply ample power output. More than likely, it was due to the fact that with a much more "beefy" PSU, the power draw from that system was so light in comparison, that it generated very little noise on the PSUs outputs (because that generally increases as power draw approaches maximum capacity, as I understand it), and was required due to the lacking of adequate noise-filtration of the power on the mobo itself.
Originally posted by: Peter
This also causes the "lost CMOS" case - this one is triggered by a 5Vstandby voltage dip in the power on phase, again a PSU weakness. Sure, augmented by the fact that this board runs the CPU off the 5V rail, but primarily the PSU not being able to keep its output steady.
I don't see how a PSU being able to keep a steady output should be a factor at all in losing the battery-backed CMOS data. Usually there's some sort of voltage-comparator/'pwrgood' signal that controls whether or not the CMOS memory is powered by the battery or the PSU. That sounds like an outright defect there that the mobo would be suceptable to that. Btw, considering that CMOS batteries are only 3v, how would dips in the 5v line cause that problem anyways? Hmm.
Actually, speaking about the 5vSB, now I remember some other sort of thing related to that on that board. It had a jumper for controlling whether keyboard/mouse soft power-on was allowed, and that chose whether or not the PS2 port (and USB?) was powered by the 5v or 5vSB lines. (My 635T-based board had that jumper too.) I seem to recall various guides suggesting to have that jumper one way or another to alleviate the issue somehow. Your right, I do vaguely remember some alleged relation between that jumper and the CMOS issue, but I cant recall nor fathom quite how it all fits together. Maybe 5vSB power isn't controlled by the 'pwrgood' signal, whereas the regular 5v power plane is, and that "noisy power" caused the issue, if that jumper was configured improperly? That's just speculation though.
Originally posted by: Peter
On the RAM end, the board is quite intolerant against underperforming RAM for two reasons: One, the SiS chipset is very very fast particularly on the SDR RAM.
That's why they invented BIOS-controllable memory timing parameters like wait-states. I suspect that the problem is probably more related to noise in the power/ground planes or the DIMM power-supply circuitry. Good boards have a seperate VRM for the DRAM array, does that board?
Originally posted by: Peter
Then of course, the four-socket arrangement does, by forces of nature, have an influence on signal integrity, again something that will not influence a good DIMM but break operation with a questionable one.
But you still only would be running with only two of those four filled, that's not that much loading on the memory signal lines. I still suspect board noise issues. Isn't that only a 4-layer board? My 635T-based board with similar layout seemed like it, it had far too much "board flex" for my liking.
Originally posted by: Peter
Nonetheless, I've run mine off a (good) 190W power supply - I had a Duron 600 in it initially - and with (good) PC133 RAM moved over from my socket-7 machine (also a PC-Chips board as it happens). No lost CMOS ever, no RAM problems, no premature death either.
Then again, some of the reports were that some boards were "good" in those regards, and some were not. Perhaps you just got a "good" one?
My view of PCChips is that they are like the "McMotherboard" company. Cheap, popular, but may give you digestive problems from time to time, if that's your only diet. More or less, it won't kill you either, at least in moderation.