Overclock Dreamcast VMU HKT-4100...

I am looking at overclocking a Dreamcast VMU HKT-4100 and struggling to locate a suitable alternative ceramic resonator to the 6.00MHz already inside it.

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I am preferably after something in the 8.00MHz range which should cover the Dreamcast being overclocked to around 260MHz. The type in the HKT-4100 looks to be an SMD made by Matsushita which, is now part of Panasonic. I am guessing from it's dimensions the part number in the attached photo may be either an EFOS or EFOSM with built in capacitor as it looks very similar in scale to that in a datasheet I found.

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Is anyone able to confirm or deny if this is true and where I may be able to purchase these from please? I have come across a seller on eBay - though the postage fee they are asking for is laughable...

Ted.

 

I should add that last resort will be to use a HC-49 quartz crystal with two ceramic disk capacitors...

Ted.

 

I have personally used a standard 2 pin 9mhz Xtal to replace the ceramic 3 pin SMD ones in the newer VMU's and have had zero issues.

I leave the middle pad disconnected, I've heard there should be a resistor between the middle and outside pads but have seen no need to do it.

Also see my post here regarding overclocking the VMU:

http://assemblergames.com/l/threads/clearing-up-vmu-overclock-misconceptions.61174/

 

Yes, that is what I'd be doing with the HC-49 crystal though I'd rather use a couple of capacitors too than chance damaging the VMU.

How far have you pushed your overclock? I already have a Dreamcast running at 240MHz without any problems at all. I am modding another one with a selector switch to turn the overclock on/off and using a chip holder for the oscillator so I can swap out different range of crystals if required. I've seen Dreamcast's pushed to 260MHz though not sure how stable they run...

Ted.

 

I've only pushed to 240mhz with a switch to change between OC and Stock. I saw no point pushing further as most homebrew and official games see a considerable speed boost at only 20%. Unfortunately the latest firmware update for USB-GDROM has broken OC compatibility in official games.

 

I'm looking into over clocking my dreamcast but I'm curious about a couple things, the guide here:
http://nslu2ultimate.weebly.com/overclock-dreamcast.html

Says to cut the IC leg? Is there any reason I can't just heat an lift the leg to do the over clock mod?

From reading above the previous post says that there is not really a point to over clocking past 240mhz, is this accurate? Is it safe to over clock any faster?

 

Yes, you can do that.

At 240MHz the extra performance does seem to iron out what very few games have minor stutters (eg. Power Stone). Unless there is a real need and purpose for it I don't think there is any justification overclocking any higher. All you will be doing is risking damaging your Dreamcast, contending with heat issues and negotiating random crashes and resets. I know because I have been there. If you really are adamant on overclocking 240MHz is the sweet spot...

Ted.

 

Some consoles do not like 240 mhz very much. Generally they appear to work, but some games show problems.

One example is Le Mans 24 Hours. Cars in the demo mode start hitting walls and stick on them instead of driving around the course. There are other examples, Ecco being one of them, again in the demo mode but i do not remember the exact problem now.

The highest stable overclock i got was 268 mhz. It made a big difference in some games, especially Ecco was very smooth. Rez was perfect!

 

How did that run temperature wise?
What size crystal does that mod require? (I'm bad at math)

 

I modified the console's case and installed extra 2.5cm fans next to and under the psu. They were pulling fresh air in, and the normal fan was pushing it out. I also ditched the default heatsink and installed low profile heatsinks on the cpu, gpu and memory. I don't really remember if it was necessary or if i did it as a precaution. With this configuration i couldn't feel any heat on the console at all. Normally, even without overclocking, the psu side gets warm to hot...

Unfortunately i managed to damage it during a disassembly session. I now use the same setup but with a board that managed only 240mhz. All this is back in my home town, so i can't really take any photos.

For the vmu i used a third party that had no cpus etc... nexus 4x if i remember correctly and it only acted as a memory unit and worked fine. Normal VMUs were getting corrupt from the overclocked console.

 

I found these on mouser https://www.mouser.com/ProductDetai...GAEpiMZZMsBj6bBr9Q9adw4h5GKfQKagNWVYgYS%2bAg=
The dimensions are similar to my HKT-7000. Going to order some as I will be overclocking my Dreamcast.

 

I tried this game to see if it happens here and I have been unable to replicate this problem whilst running in demo mode.

I ended up finding and purchasing Panasonic EFOS 7374E5 ceramic resonators. They work just fine in the VMU I have here...

Ted.

 

I would lift the leg. I don't do anything to my consoles that I can't reverse. The Dreamcast takes the clock input and multiplies x2, then the CPU applies an internal multiplier of x3. So for 240mhz use a 40mhz clock, for 270 use a 45mhz clock. As @Teddy Rogers said, 240mhz is the sweet spot. 270mhz is the upper limit but active cooling would be needed. 300mhz is unstable, I don't think anyone has succeeded in this overclock. I would install a switch and just run an overclock on games that support it. A PLL chip could be looked at if u wanted to design a pcb to switch between several clocks on the same console.

 

I don't mean to derail the thread, seeing as I bring nothing to the table here, but what's the purpose of overclocking the VMU?

 

When you overclock the Dreamcast, you need to overclock the vmu as well. Otherwise, you get corrupt saves.

 

Ah, thanks for the answer.

 

Overclocked my VA2 dreamcast and my green VMU. Both are working great, the vmu with the ceramic resonator I linked above is a very nice fit.

 

could you show me where is the resonator please ?

And there is a good mod for overclocking and where we can found the stuff for it ? I found the mod of family guy, there are others ?

 

If you compare the 2 pictures I uploaded, you'll see it, in the center of the vmu. It's a little black rectangle.

This is the link for the USA

I believe all the Dreamcast overclock mods are the same. Although it is said that some Dreamcast VA2 motherboards don't like to overclock. It's a hit or miss, apparently, I hit it pretty good.

 

I would guess that any VA2 boards after November of 2000 would have issues with the overclocking as those are the ones with the patched security, but that's just a random guess.