IBM
Hardcore vintage 486 hacking for overclocking
Hardcore vintage 486 hacking for overclocking
#Hardcore #vintage #hacking #overclocking
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You should look at enameled wire for trace repair perhaps? They are much smaller and would be much easier to route.
Frankly I'm glad the board didn't fly! It looks nice, it should stay nice and safe on the bench and not fly somewhere and get wrecked!
I do recall back in the day, my Cyrix 80Mhz could consistently outclass faster CPUs w/ 33Mhz bus… in certain workloads, it seems to matter a lot more than I would expect. I suppose Doom uses a lot of bus time, so it adds up.
Most multimeters don't measure frequency. Those that do are usually cheap chinese ones and usually only measure up to 10MHz. You will need to buy either a dedicated frequency meter or just use the scope. You're not measuring frequency that often and you already have the scope so just use that. No need to buy another multimeter.
1. Buy a (used) frequency counter instead of a new DVM, as otherwise recommended. 2. look for a 133ADZ (instead of 133ADW) type CPU which is supposed to be better suited for overclocking (no guarantee however).
Looked up the GD5424, it is a VLB chip
Danke!
My first PC was the 33 MHz dx version
You may need to adjust the ISA bus multiplier to support higher than 40MHz. Assuming that option is visible in BIOS?
As others have said a heatsink with some weight and a fan is good when using these 586’s.
In my personal experience they don’t like doing 150-180mhz without extra voltage. To stabilise 160mhz I have always needed additional voltage, they scale well with volts and this will likely fix your stability issue 🙂
18:20 no they aren't 😉
Pro tip: Take a single strand of bare wire from a multi-strand wire cable. That wire is 0.15mm wide which is less than the width of the trace. Bare the trace, apply flux/solder to the trace and the wire then solder the tiny wire to the trace directly but only at one end. Bend the wire using tweezers so it is the same shape as the trace and continue along the trace soldering it down. After it is done cut off the excess piece so only a tiny wire remains bridging the cut. I've done this kind of repair probably 500 times on arcade boards over about 30 years of repairing stuff
That Cirrus is clearly on local bus, those speeds are impossible on ISA bus. But, because Cirrus 542x is only a 16bit chip the speed is still half of faster VLB chips. Cirrus 543x chips are 32bit and with 40MHz VLB clock it takes almost 40Mb/s 🔥 By the way, if 5×86 won't take 160MHz then it is 150MHz so FSB to 50MHz X 3. 😁
I'm a professional and only use Fluke and Keysight meters. Even a second hand Fluke is a good buy.
Good morning. How you upgrade the cache. What support chips did you use . IDE and video probably is in local bus
There is a small standby supply in the PSU so it can be turned on with the push of a button, it's probably where the noise is coming from. By the way, I always replace the small capacitors on the mains side of a SMPS and it often fixes the problem. It's quicker to eliminate them before looking for other problems.
I suspect you have a ripple problem. Considering the 487 socket was never intended for running power hungry CPUs it probably doesn't have enough capacitance on the power rail. Try adding some additional bypass capacitor close to the socket on the 5v rail.
I wonder if there is any value of wrapping those caps close to the heatsink with a little bit of Kapton tape.
I just use the oscilloscope to measure frequency for anything over a couple of MHz. And if possible I'll use the spring attachment to minimise the ground loop, although that's probably unnecessary if you're only looking at the frequency and not the shape of the waveform itself. Also be careful inserting pins into the socket, it's possible to push the contact inside at the wrong angle and bend it so it no longer makes a good connection.
It's a shame you didn't fix the power supply, but it's good you've got a spare. I'm a little surprised that it actually turns on. Usually that kind of ticking noise is the power supply failing to start because there's some issue with the bootstrap circuit. There's usually an auxiliary winding on the transformer which charges a capacitor to run the controller chip, and if that capacitor never charges enough to run the controller chip, it will just constantly pulse the transformer at that low frequency, causing that ticking sound. So I would usually suspect either the capacitor or the diode on the auxiliary winding when I hear that ticking noise. But yours actually starts, and is only making the ticking noise when it's off, which is really weird because it means the bootstrap circuit is fine.
You cant do 133/160MHz without fan and heatsink with thermal compound… it's printed on the cpu "fan/heatsink reqd"
The ones you want for overclocking are the ones marked with 133ADZ. the ADWs don't overclock nearly as well.
adjust your voltage regulator on the interposer to provide 4V. this will overvolt the 5×86 but almost guarantee at least one of them will be stable at 160MHz with the overvolt
The 5×86 that almost booted dos (nr. 3 was it?), reminds me that when I overclocked those CPUs, I had same results (booted dos ok but it would no run anything, it freezed at minutes after boot), until I used a properly mounted heatsink with fan; even then, sometimes it liked to hang and freeze, until I used thermal paste (it was the first time in my life to use thermal paste on a ceramic CPU) and only then I could run Win95. It seems to me that your CPU can run at 160MHz but you really need to cool it down. (or play a bit with its voltage?).
The coil in your PSU may be singing just because the ferrite core vibrates; it may had became a bit loose, try to wiggle it to see, that may be the case. Adding a bit of silicon will fix the noise. Many coils I saw had a bit of glue or silicon to prevent them to vibrate (especially those working at audible frequecy), that noise seems to be the mains frequency. Electrically and functional it works ok.
Why didn't you use a wirewrap tool on the pins? That would have worked great and the gauge of the wire is easier to work with . Not criticizing what you do, because you do great work. I was just curious..
That is an epic repair on that sound card! Excellent work!
Amazing work as always!! You forgot your happy cap marker!!! 😊😂 I also agree, that ESS card is worth it – most vintage stuff is!
for a completely dead PSU, you should check the smallest caps in the primary area (everything before the secondary heatsink/rectification).
Especially Caps right next to heatsinks or between heatsinks and coils…
Caps with 6,3mm Diameter and lower like to dry out and go bad that way.
I bet that the graphics chip uses VLB and 40MHz FSB is too much for it with 160MHz.