Does my Midway Space Invaders have a hack on it?

Tighe

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Is this normal? For the 20 seconds total I have been able to play it with this flaky power supply it seems to play much faster. That is a 27 mhz crystal there... The old guy who gave it to me said he has had this game since about 1983.

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Is this normal?

Nope. It looks to be some type of mod. But it's an old one, based on the date codes on the ICs on it. In a stock Midway PCB, the crystal is in those two large holes visable on the left in the first photo you posted.
 
Nope. It looks to be some type of mod. But it's an old one, based on the date codes on the ICs on it. In a stock Midway PCB, the crystal is in those two large holes visable on the left in the first photo you posted.

Thanks for the info Darren! Anyone else ever seen this mod before??
 
Love the video of the gameplay, and congrats on getting it up and running. I would love to have a speed hack like that on my SID. I run the 8in1 on it, which is cool, but that speed hack is BOSS....
 
Love the video of the gameplay, and congrats on getting it up and running. I would love to have a speed hack like that on my SID. I run the 8in1 on it, which is cool, but that speed hack is BOSS....

It really is, Before I got this running and knew there was a speed hack in it I figured I would trade it because I find SI too slow to be fun. But this really makes a huge difference!!

I wonder if the speed hack could be combined with the 8-in-1.
 
It really is, Before I got this running and knew there was a speed hack in it I figured I would trade it because I find SI too slow to be fun. But this really makes a huge difference!!

I wonder if the speed hack could be combined with the 8-in-1.

I'd be curious to find that out as well. Logically, I would say no, it probably wouldn't work... but I would love to be proven wrong. :) A lot of it depends on WHAT it is doing to speed the game up.

Regardless, you might want to have that mod looked at, documented, and possibly reverse engineered if no one has really seen this before. Someone might be able to make some money off of this.. ;) (And you got the damn thing for free...)
 
I'm willing to bet the 8-1 kit will work fine with this mod.

All the crystal is doing is making the 8080 run a bit faster. As long as the crystal isn't crazy faster than what the Intel can handle itll run, faster crystal = faster gameplay. If the new clock isn't causing random resets you should be good.

Any chance you can take a pic of the underside of that board? I'd like to build one of these myself, maybe make an adjustable clock so that you can choose just how fast the game runs :D
 
I'm willing to bet the 8-1 kit will work fine with this mod.

All the crystal is doing is making the 8080 run a bit faster. As long as the crystal isn't crazy faster than what the Intel can handle itll run, faster crystal = faster gameplay. If the new clock isn't causing random resets you should be good.

Any chance you can take a pic of the underside of that board? I'd like to build one of these myself, maybe make an adjustable clock so that you can choose just how fast the game runs :D

Sure no problem. A pict of the daughter board right?
 
yup yup! thanks man

Just need to see where those traces are going to from the crystal and making a new board to test on my SI with the 8-1 kit should be a piece of cake
 
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Wow! I'd be interested in one of those as I should have a SI at the end of the month. It would be awesome to be able to speed up gameplay.
 
Wow! I'd be interested in one of those as I should have a SI at the end of the month. It would be awesome to be able to speed up gameplay.

If I can source the parts reliably enough I'd be more than happy to build a few for whoever wants one

Otherwise I fully intend to release the schematics anyway so anyone can build one (if Tighe permits, its his board after all). The thing looks so rediculously simple, it can't be hard to reproduce
 
It's a 27MHz crystal, the original was just uner 20MHz (19.968). So that's about a 35% speed-up. The original 8080 was rated for 2MHz, however third-party and later versions may have higher speed ratings. So it may be "overclocking" the CPU. Of course, the EPROMs and RAMs and all the TTL also get operated faster... but it appears to be working fine for you.

I'm not sure how this hack handles the video sync rates. I'm a little surprised that the monitor can sync at a rate 35% higher (i.e. 60Hz * 1.35 = 81Hz) for the vertical rate, and 15kHz * 1.35 = about 20kHz for the horiz sync. Those sound high... it'd be worth a little time to look carefully over the board to see if any traces are cut, or jumpers placed, etc., to tweak the video sync frequencies.
 
it'd be worth a little time to look carefully over the board to see if any traces are cut, or jumpers placed, etc., to tweak the video sync frequencies.

Good point, didn't think of that. Unfortunately I know diddly squat about video signals, I thought the SN74S04N had something to do with it, but I dunno

I've got all the parts sourced, just waiting on Tighe and I can start building. Want me to scrape you one together if it works jbk?
 
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I'd take one of these too. I have a SID with the Braze kit, and would be curious to see if it would work together.

Heck, let me know what the kits would cost, I might take parts to make 2-3. I know a few guys in the area that have SI's who would want one. I could put them together, just need the components and a schematic...
 
Concider it done Guru!

The kits prolly won't cost much at all honestly. Just need the schematic
 
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Good point, didn't think of that. Unfortunately I know diddly squat about video signals, I thought the SN74S04N had something to do with it, but I dunno

The S04 is presumably replacing the two gates in the crystal oscillator circuit at A7 (snip from schematic attached). The two resistors & the capacitor also presumably replace those on the PCB right next to the original crystal. The socketed component (74160) is equivalent to the component on the schematic at C7 (9310, also see attached snip).

I can pretty much guess how everything on the little PCB is connected, but I'd still be curious to see a photo of the bottom side, if the OP is willing to share it.
 

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