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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 1st Oct 2017, 12:44 pm   #21
Biggles
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Default Re: Old arcade games

It's unbelievable Chris, when you think that nowadays even the simplest software seems to need acres of memory. The graphics were still pretty good if I remember right. Some of the tubes looked like the pixels were almost oblong, but maybe this was down to the tube rather than the software? I remember many a happy night playing Galaxians and Space Firebird. The sound effects are still clear in my head.
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Old 1st Oct 2017, 2:13 pm   #22
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Default Re: Old arcade games

Quote:
The graphics were still pretty good if I remember right.
For the time (and nostalgia) perhaps, but people want reality now and that costs resources. With the crash in the cost of memory the whole computer experience is now about presentation as much as than substance, like it or not!
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Old 1st Oct 2017, 2:22 pm   #23
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It was the eighties, and I was but a teenager, and for the time it was cutting edge. You are right, nobody would accept those graphics nowadays, what with 3D UHD and the like. But it was of the time. Rose tinted spectacles and all that. Things don't seem half as exciting nowadays...
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Old 2nd Oct 2017, 2:43 am   #24
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In my view, many of the coded versions of the original arcade games like Pong, Tank, Asteroids are very poor facsimiles of the real thing. Its better to get the real arcade boards/games if you can.

Even going back to the simplest examples, the reason coded (PC) based versions of the original ARCADE Pong were poor compared to the originals was because the coders had no knowledge of the original Pong circuit architecture in terms of the way it operated and made the game play.

For example in Pong, it turned out after the circuit analysis was done there were 42 states of motion of the ball and the specific paddle and ball interactions were elucidated.

The reason this wasn't common knowledge prior to the year 2012 publication cited below was that Atari didn't publish a "functional analysis" only the schematic....and it was not self evident from looking at the schematic what was happening. The circuit analysis was in fact "missing". This left the coders in the dark, so what they made looked like a pong with the ball bouncing off paddles and the screen edges, but it played quite differently.

(just like coded versions of other classic arcade games)

I wrote a very detailed description of Pong's circuit architecture which revealed the details, including the 42 states of motion, but even then, as explained in the article there was a PCB defect in the original Syzygy pcb's that reduced these (now called the Ghost in the machine bug) there were actually 6 bugs, also it contains interesting remarks from an interview with the inventor, it is here:

http://worldphaco.com/uploads/LAWN_TENNIS.pdf


Still, I have yet to come across a computer version that plays anywhere near as well or similar to the original Arcade version. The closest would be one implemented with an FPGA by a fellow in Germany. The same applies to Tank & Asteroids, but of course many people not particularly familiar with the subtleties of the original Arcade games would be perfectly happy with the coded versions. Also people were generally happy with the home Pong game, but many compromises were made when they forced the 66 TTL IC's of the original arcade pong into one LSI IC.

Another related article is here on a miniaturized version of the arcade pcb which discusses the bugs in more detail:

http://worldphaco.com/uploads/ARCADE_MINI-PONG.pdf
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Old 2nd Oct 2017, 10:21 am   #25
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Default Re: Old arcade games

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Originally Posted by Biggles View Post
It's unbelievable Chris, when you think that nowadays even the simplest software seems to need acres of memory. The graphics were still pretty good if I remember right. Some of the tubes looked like the pixels were almost oblong, but maybe this was down to the tube rather than the software? I remember many a happy night playing Galaxians and Space Firebird. The sound effects are still clear in my head.
Alan.
The pixels vary in size and shape, but almost all of the first generation of raster-based video games used NTSC-like timing but non-interlaced, typically 262 lines or thereabouts of which typically 192 are used for picture information. The CRT was typically turned sideways so the lines were actually columns, and the field scan was actually horizontal. The resolution in the other axis (horizontal in conventional video, vertical in reality) depended on the pixel clock speed, but 6MHz was quite common, giving 256 pixels in an active video period of about 42us.

One of the things I find fascinating about the design of these games is the amount of electronics devoted to creating the video display. There are typically anything between 50 and 200 or more TTL logic ICs, most of which spend their time doing something to do with the graphics. The whole thing is optimised to play only the game it's designed for. Galaxian, for example, couldn't draw a circle or plot a graph. It can only draw aliens! However, it can do it in real-time, to give the smooth movement and quick action that the game needs.

As a budding home computer programmer in the early 80s, it was a source of frustration to me that I couldn't match the graphics performance of the games I saw in the arcades, using a home computer's general-purpose graphics capabilities. Decades later, now I can understand why!

Chris
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Old 2nd Oct 2017, 10:25 am   #26
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By way of example, here's a picture of the circuit board from the classic Atari game 'Missile Command', dated 1979. You can see the sheer number of TTL chips involved. This game is actually rather unusual because it has (more-or-less) a general-purpose bitmapped display, but it happened to be on my desk

Chris
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Old 3rd Oct 2017, 1:36 am   #27
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That is a very lovely pcb !

One other thing I could have mentioned in my last post, is that the way the old arcade games played also had a lot to do with the player interface. In pong for example it was two Allen Bradley 5k pots with large knobs. In Tank it was a dual control handle pairs.

When these games are adapted to computers the Joystick interface is often hopeless compared to the original Arcade system. It can be worse...

I was contacted by a fellow coding a Pong game into a PIC microcontroller for use with an LCD screen. He had read my paper on how Pong worked, but he was baffled about one thing.....what was it that controlled the speed of the paddles ? So I explained it was the speed that the player themselves rotated the physical control pot which related to the skill of the player. That was a shock because all he had for the interface were two up-down buttons to move the paddles and no pots.

So not only are there many deficiencies in the way many original Arcade games get coded that don't match the functionality of the original game, the player interfaces are not the same either.
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Old 3rd Oct 2017, 8:22 am   #28
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I haven't a clue with computers, but I love old video games.
I met an enthusiast once, and asked him how I would go about learning to build-up JAMMA
cabinets with original boards.
He said "First of all, you need to start in the '80s..."
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Old 3rd Oct 2017, 9:07 am   #29
cmjones01
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Originally Posted by Argus25 View Post
One other thing I could have mentioned in my last post, is that the way the old arcade games played also had a lot to do with the player interface. In pong for example it was two Allen Bradley 5k pots with large knobs. In Tank it was a dual control handle pairs.

When these games are adapted to computers the Joystick interface is often hopeless compared to the original Arcade system. It can be worse...

I was contacted by a fellow coding a Pong game into a PIC microcontroller for use with an LCD screen. He had read my paper on how Pong worked, but he was baffled about one thing.....what was it that controlled the speed of the paddles ? So I explained it was the speed that the player themselves rotated the physical control pot which related to the skill of the player. That was a shock because all he had for the interface were two up-down buttons to move the paddles and no pots.

So not only are there many deficiencies in the way many original Arcade games get coded that don't match the functionality of the original game, the player interfaces are not the same either.
Yes indeed. I have a collection of original (and bootleg) arcade PCBs which I can play by plugging them in to a JAMMA harness. One of the challenges has been recreating the original control methods: a diagonal joystick for Q*Bert, for example. My most recent addition has been Atari Super Breakout, which originally used an analogue paddle like Pong. Since I'd added an FPGA to generate the screen colours and indications which would have been done by light bulbs on the original machine, I added some logic to encode a quadrature trackball (or mouse, indeed) and emulate the original paddle. It works really nicely. The code I wrote also supports using a joystick for the same job, but it doesn't feel right: direct control of the paddle position is a must!

Chris
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Old 3rd Oct 2017, 9:10 am   #30
cmjones01
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Quote:
Originally Posted by Brigham View Post
I haven't a clue with computers, but I love old video games.
I met an enthusiast once, and asked him how I would go about learning to build-up JAMMA
cabinets with original boards.
He said "First of all, you need to start in the '80s..."
Ha! Don't be afraid. They're delightfully simple really. The vast majority of games just take +5V and +12V power, control connections up/down/left/right/fire/coin/start, and RGB video out. The wiring is usually just a rearrangement of the same signals on a different connector.

Getting the original boards working properly can be a proper challenge, though.

Chris
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Old 4th Oct 2017, 12:06 am   #31
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Originally Posted by Terry_VK5TM View Post
Basically a little circuit that detected (via a short aerial) the static discharges and prevented credits being racked up.
The circuit in Atari pong consisted of 3 transistors in a set-reset configuration, the "antenna" was simply connected to the transistor's base, there was no base resistor, just diode backwards across the BE junction, so the collector-base leakage charged the b-e junction up and it sat just below the threshold where there was any significant collector current. Then if a static discharge occurred, or a burst of RF, it immediately reset the game.The circuit is described in the article I posted above.
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Old 4th Oct 2017, 11:40 am   #32
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That sounds like what we used (unfortunately, all the paperwork I had on this disappeared about two divorces ago).

Being so long ago, the fine details are lost in the memory fog, but I have a vague recollection that we were supposed to wire them into the credit switch circuit somehow.

The little pcb, which I think was about 1/2" by 3/4", was stuck to the coin door with double-sided tape.

We used to install them into everything - pinballs, table-tops and uprights.

Terry
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Old 4th Oct 2017, 12:31 pm   #33
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That sounds like what we used (unfortunately, all the paperwork I had on this disappeared about two divorces ago).
I've attached the circuit of the one used in Pong.
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Old 5th Oct 2017, 1:45 am   #34
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Thanks Argus25.

I did have a quick look at your PDF, but I will save this for future reference.

Haven't done any Game/Pinball servicing in a while now, other than a mates Firepower pinball that needs some TLC.

Terry
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