The processing power didn't change a whole lot. For example, classic bally/stern used a 6800 8-bit CPU which ran at 1MHz. WPC games ran on a 6809 16-bit 2MHz CPU.

Computers during the WPC era were generally running at 60MHz in 1993, slowly increased up to 800MHz throughout the span of the 90s, and eventually broke the 1GHz barrier in March 2000.

One thing that did change rapidly was sound technology. Which is why sound chips & amps always seem to be hard to obtain today--they were only made for a short time before being discontinued and moving on to the next latest and greatest thing.

Display technology also leaped ahead in fits and spurts, but not nearly as quickly as sound tech.

But generally, the CPU in pinball machines didn't need to be too powerful. It followed a few simple if-then instructions and did some simple addition and multiplication, and that was about it.

1. Sound ability (whole separate CPU, often running faster than the main CPU)
2. Playfield design
3. PROM space: Sys3 had maybe 2KB of space for all its code, WPC had up to ~2MB iirc. Also cheaper ROMs meant more sounds
4. Competition with their older games (if your games aren't getting any 'better' it looks bad, so you need to keep outdoing yourself and your competitors). Technically, besides from a fancier sound, Black Knight and Hot Tip run on HW with the same capabilities, but they didn't make Black Knight then, because they didn't need to

ALIEN POKE HER......you deal.......

Mad powerful. Many gigaflops and terahoozits.

Comparing with computers of the late 70's and 80's is a tough comparison, because it wasn't until the mid to later 80's that people were really buying home computers. Obviously the servers of the time were much more powerful. And code applications and compilers were different than what was done with pinball.

Pinball MPUs really were using relatively inexpensive off the shelf processors & RAM for the most part, so they weren't overly powerful in comparison to even some of the home systems that were available. x86 & 680x0 processor based machines of the time were much more powerful.

So to answer your question, they weren't powerful for the time because they didn't really need to be. Technically they still don't need to be. You can build a happily functioning pin with an ATmega256 microprocessor. They only had to run fast enough to catch and register switch hits and run simple subroutines. And since they were programming these in straight-up assembly, they had the ability to maximize the order in which things occurred as to not clog up the CPU cycles with useless instructions and loops. In other words, these guys did amazing stuff with code.

What really is interesting was the choice to use the 6800 processor by Williams when the 6502 was available at a much cheaper price with roughly identical specs. Gottlieb took advantage of this, but they were the only ones. I don't know the full history behind those choices though.

The early bally computer runs at 0.6MHz, have 256x4bit + 128x8bit of RAM, and used 4kb of software. Its a pretty amazing they pulled off great games with so little.

Pure code. Really efficient ASM programmers that understood priority of instructions. It blows my mind when I watch the VPinMame Debug window and I see how quickly the CPU will get out of subroutines, with seemingly no time to spare, all while juggling all the other data being sent all over to the various peripherals. These guys were undoubtedly knee deep into the mechanics of the game layouts as well, not just code monkeys. I'd love to hear from some of the earlier game original programmers. They don't get as much recognition and credit as the layout designers and artists.

Bally multiplexed to the extreme. The PIAs do amazing work in these games too toggling between updating displays, reading switches, etc.. Bally uses two PIAs, WMS was using 4 or 5 in the same era.

Anyone know who was the main engineer when designing the Bally -17 electronic board set?

I can only image how much of a PITA programming on the Bally board must have been...at least initially while they were figuring out how to juggle everything. Programming in Assembly is not fun unless you're making a drinking song in it.
http://www.99-bottles-of-beer.net/language-6800-assembler-2423.html

That's the thing - there's no layers of crap over top slowing stuff down. No OS, no graphical interfaces, nothing but direct hardware addressing.

Can you imagine how fast modern computers would be without so much cruft?

I also wonder at the choice of the 6809 vs. 6502.

The 6809 was more advanced at the time, and from the article says, easier to write code for.

https://en.wikipedia.org/wiki/Motorola_6809

I'm not sure if they had more complex code or just better designed rules. Starting with system 7 Williams actually had a sophisticated, multithreaded byte code operating system allowing them to fit more rules in less ROM space. I've also noted Williams games tend to have a lot of sophisticated lighting effects (the pulsing bonus counter or the animated displays during multiball on black Knight, for instance). Stern and Gottlieb also supposedly switched to a state based architecture, while bally didn't make any changes, according to some things I've read, which supposedly caused them problems

There are advantages to both processors. The 6809 was apparently easier to program on and had more hardware registers (I think 6, vs 3 on the 6502). That right there could have been the crucial decision point. The 6502 was pipelined, which allows it to process more stuff in a single cycle.

I actually meant the 6800, which was out before the 6502.

I asked an industry veteran and he pointed out an important fact - Motorola was only 15 miles away from Williams on California Ave. compared to MOS, who were down in SV. So, proximity probably played a big role, as well as timing.

I think the xbox and PS dedicate a single core to the os if I'm not mistaken.

It is amazing to think about early SS games when they were new. I remember when calculators were new and expensive.Digital watches were LED and you mashed a button to see the time. Really cutting edge technology for the time. Cash registers and gas pumps I remember the old ones. I recall seeing my 1st SS Mata Hari and Power Play back in 78. And look at us now.

The 6803 is a rock solid design, definitely the best of the era. A shame it was the end of Bally on its own. They really managed to get huge mileage out of very little, considering the sounds deluxe near the end on some of those games was much more powerful than the MPU, using a 68000 CPU. For comparison, the Capcom SYS-1 CPU is entirely driven off of a 68000 CPU, a Z-80 (gameboy), & a Raster Display IC. CPS-1 was Street Fighter II, Strider, Ghouls & Ghosts, Magic Sword, etc.