Author Topic: Dreamcast Overclock Plus VMU overclock.  (Read 507 times)

Offline Gizmo613

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Dreamcast Overclock Plus VMU overclock.
« on: November 17, 2017, 06:12:56 AM »
Hey guys, I'm back without another one of my Dreamcast mods.  This time it is an overclock of the Dreamcast system and the VMU to match. VMU needs to be overclocked to match the Dreamcast new speed. Otherwise corrupt game saves will be encountered. Recommend you back up your game saves first before attempting this.

Note: I am not responsible, nor Acidmods, for any damages you do to your Dreamcast or yourself should you follow this guide I had set up.

Dissembling the Dreamcast is very easy so I won't upload any pictures of that. Basically, remove the screws on the bottom and remove the top half cover. Then unscrew power supply, GD-Rom lens, and controller port. Followed by the heatsink/metal shield. Voila! Easy peasy.

Dreamcast VA2 Motherboard:


Pin 1 = NC(no connection)
Pin 2 = GND
Pin 3 = Output to Dreamcast points A or B
Pin 4 = VCC

The area is just below the power supply pins. The oscillator frequency is 40MHz. Also, there is a jumper resistor labeled at R331 that connects the PLL chip to the Dreamcast SH4 chip. Remove this jumper resistor, otherwise, you can do it the hard way and try to lift the legs of the PLL chip. I find removing the jumper is easier and if I wanted to go back to stock, then I would just solder the 2 points together with a solder bridge or lead wire.

Once finished, the Dreamcast will now run at 240MHz vs the stock 200MHz. For me, I noticed a difference when playing 3 games. Tokyo Xtreme Racer 2, Skies of Arcadia and Grandia 2.

TXR 2 is known to lag/stutter when a race is about to start or when the replay is being viewed. This is especially the case with backups and rips. The original disc has some stuttering as well but not as much. I have both the original disc and a ripped copy and the ripped version plays flawlessly. I have no doubt that the original will also play without stuttering.

A few Grandia 2 rips also stutter consistently as well. I have Taiyo Yuden CD-Rs and I burn at various speeds and all rips stutter and skips at the same position. But with the overclock, all the rips runs very smooth! My original disc is being delivered today so I will be playing it this weekend.   :tup:

And then there was Skies..... Well if you played this on the Dreamcast then you should know what happens, LMAO. I'll keep it short and say the above results will be the same here.

And now the VMU overclock:
Remove old crystal first


New Crystal


Remove the battery cover and batteries by removing the screw on the back of the VMU.
Then remove the 4 screws in the corners.
Carefully separate the back cover as the speaker is glued to it and the wires are soldered to the PCB.
Remove the 6MHz crystal and replace with the new crystal.
I used an 8MHz crystal from Mouser. Will link to it if it is allowed. Minimum value needed is 7.2Mhz if you are overclocking the Dreamcast to 240MHz. But the VMU can be used if it is overclocked a bit higher than the Dreamcast.

That's it! Enjoy!  :drunk:




Edit:

These Dreamcast Revision are running stable @240mhz
Dreamcast VA0
Dreamcast VA1
Dreamcast VA2 (Before November 2000 manufacture date And some November 2000 dated VA2 board) (Mine is a October 2000 revision)

This one is not so stable
Dreamcast VA2 (After November 2000 date - Not stable try a lower frequency- Don't have one to try though so I can
t confirm)
« Last Edit: November 17, 2017, 08:04:32 AM by Gizmo613 »

Offline Brian 503

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #1 on: November 17, 2017, 07:09:06 AM »
Nice write up! So if memory serves me correct the dreamcast overclock is done with a 40mhz crystal oscillator correct? I did this once but I lifted the pin to overclock with switch to flip back and fourth to overclock to stock. I tried reading up on the vmu overclock for saves but never got that far. I like the method u found for wiring the oscillator to the dreamcast board! So u do have success with saves when overclocked now?

Also curious do you run your dreamcast with standard rgb cables, S cart or vga?  I did the vga internal mod but now with external vga boxes on the market I find those much easier. The only thing I don't like about the vga boxes is the sterio port. Gives out poor volume and only runs off of one speaker (No L/R). Anyways looks awesome. Might have to blow the dust off the dreamcast and go on ebay and get Tokyo stream racer 1 and 2. That game was sooooo  sick.

Offline Gizmo613

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #2 on: November 17, 2017, 07:25:14 AM »
Yes, 40mhz crystal. I won't add a switch since most of the games I play run fine with the overclock. Only some games will run faster due to the increased speed is done by overclocking. Some games actually are hardcoded to run at a certain speed and with the overclock increase, those games will run at an increased rate as well.(Like watching a movie with the fast-forward button stuck.) Not sure if I'm explaining that properly.

Played all 3 games I mentioned and it all saved and load just fine. I have a VGA cable that I purchased from eBay for about $12 or $11. Works great but on my 46" Samsung there is an annoying hum when playing TXR2. Told the seller and he refunded me the total purchase. The VGA cable has an L/R stereo output. You might need an adapter to convert it to a 3.5mm headphone jack as that's what my tv allows for a VGA connection.
The game looks ABSOLUTELY amazing on VGA with widescreen enable plus Overclocked! Cars look more defined. I have never seen a sexier Honda CRX.

Next Mod, HDMI!!!!!! I hope it will work though as no one seem to have built or confirmed if it works. At least for the one that Citrus3000psi designed.  :winker:

BTW: I modded the orange led to Green, and I was nearly blinded since I ran the Dreamcast without the top half cover, lol.
« Last Edit: November 21, 2017, 10:38:42 AM by Gizmo613 »

Offline RDC

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #3 on: November 20, 2017, 07:11:38 AM »
RDC and OzOnE ;) No way I could pull that project off alone, and it's really turned into a bear for both of us.
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline Gizmo613

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #4 on: November 20, 2017, 07:54:03 AM »
RDC and OzOnE ;) No way I could pull that project off alone, and it's really turned into a bear for both of us.

Wait....so Ozone is Chris!? I knew oZone was ElectronAsh. I should his 60 fps TXR video on youtube and that got me started for the search of an HDMI mod for the Dreamcast.

Offline RDC

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #5 on: November 20, 2017, 03:10:09 PM »
No idea who that Chris is, Ash is how I know him.
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline Gizmo613

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #6 on: November 21, 2017, 06:30:39 AM »
Have you guys only done testing on the Dreamcast with this board? On the shmups forum, the creator said that he wants this to be used on multiple consoles and not just the Dreamcast.

Offline RDC

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #7 on: November 21, 2017, 08:29:46 AM »
It actually started it's life as an 'all in one' type of idea, but I finally had to talk him out of that and get onto a one console, one board design, as it's a massive, massive PITFA to try and do one board for 2 consoles, let alone multiple ones. This thing actually was first soldered up to a GC, but we shifted to the DC soon after, then we plan to go back to the GC at some point, as well as hit the PS2, original XBOX and some other older consoles. Some night say that versus doing a different board design for each console might be a huge pain, but for me it's not and it lets each different layout get used the best for mounting and such. Trying to make a universal HDMI board, all you end up with there is a dev board that doesn't fit into anything nice and neat at all.
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline Gizmo613

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #8 on: November 21, 2017, 09:00:29 AM »
ah yes. Yeah, I was wondering how progress was going. Nice to see that it is a dedicated board to the console. At this point, I am waiting on the USB-blaster and boards to come in. Everything else is here and waiting.

Also, isn't the GC hdmi done? I've seen your post with pictures and they look great.

Offline RDC

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #9 on: November 21, 2017, 09:04:31 AM »
Uh, what post?
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline Gizmo613

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #10 on: November 21, 2017, 09:51:11 AM »
Nevermind, I got you confused with another person.

Offline Brian 503

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Re: Dreamcast Overclock Plus VMU overclock.
« Reply #11 on: November 21, 2017, 03:22:54 PM »
I've been waiting almost 2 years now for bad ass consoles to finish and release the GC HDMI plug and play. I've tried contacting him multiple times with no luck. At this point I feel I was shafted 80$. I'm pretty pissed about it.