General Instrument CP1600

[juice2839]

Anyone have a busted up junker parts console. I have a really nice console with only a bad CP1600 (CPU). Also I have another one that needs a left side controller if thats decent on a parts console. I know fixer uppers go cheap on ebay, but I kinda cringe when I have to destroy one to make another one good. If someone had one that was physically busted or pretty much junk but good parts at least its better then wrecking another one that can be fixed.

 

Thanks in advance.

[intvnut]

Are you certain the CPU is bad? Have you tried swapping just the CPU with another working system? (I'm assuming an Inty 1 with socketed CPU.) I guess my question is: How do you know the CPU's bad and not something else?

 

I've seen the clock driver transistors next to the CPU go bad, which will make the CPU not function. These are cheap and easily replaced.

[juice2839]

Are you certain the CPU is bad? Have you tried swapping just the CPU with another working system? (I'm assuming an Inty 1 with socketed CPU.) I guess my question is: How do you know the CPU's bad and not something else?

 

I've seen the clock driver transistors next to the CPU go bad, which will make the CPU not function. These are cheap and easily replaced.

 

Swapped out the CPU and the unit worked perfectly.

[pimpmaul69]

 

Swapped out the CPU and the unit worked perfectly.

i have 3 boards lying around. Need to get a system running first then i can send you one.

[juice2839]

i have 3 boards lying around. Need to get a system running first then i can send you one.

 

Cool. Thanks.

We should start a thread with symptoms and repairs. I just had one that the transformer got really hot and the game would come up 1 out of 4 tries. It ended up having an open diode on the power supply.

Edited December 25, 2014 by juice2839

[intvnut]

 

Swapped out the CPU and the unit worked perfectly.

 

Gotcha. Yep, sounds like a bad CPU then.

[JohnPCAE]

Has anyone ever thought about making a pin-compatible replacement with an FPGA? The CPU runs so slowly that it seems like it shouldn't be hard to do (though admittedly I don't know anything about FPGA programming).

[intvnut]

Has anyone ever thought about making a pin-compatible replacement with an FPGA? The CPU runs so slowly that it seems like it shouldn't be hard to do (though admittedly I don't know anything about FPGA programming).

 

I know Kevin Horton has done a full Intellivision in FPGA.

 

I've toyed with doing bits of an Intellivision in microcontroller, actually. The CPU's slow enough you don't need an FPGA to meet all the bus protocol and what-not and remain cycle accurate, I'm almost certain. With a PIC24H @40Mhz, you have about 45 microcontroller cycles per CPU clock. When you consider the average CPU instruction takes 8 cycles (and the fastest take 4), that's more than enough time when your only job is to emulate the CPU. Most CP1600 instructions could be emulated on that MCU in 1-2 clocks. The rest of the time is bookkeeping for the flags and asserting bus phases on schedule.

 

(I guess to keep it locked to the bus clock, you'd probably have to run at some multiple of NTSC colorburst, such as 35.79545MHz, or 39.374995MHz if you could coax a 11x multiplier out of the PLL. Still, more than enough cycles to make it work without having to learn Verilog or VHDL.)

Edited December 28, 2014 by intvnut

[juice2839]

All very possible, but with a parts INTY at about $20 it's not worth it for me to do all that work . Might be easier to rewrite or port the games for a different processor LOL.

[HunterZero]

A modern drop in replacement RA-3-9600 RAM chip and AY-3-8914 PSG would be really useful too. Perhaps the RAM could be onboard with a drop in replacement CP1610? Might need a null passthrough for the RAM socket then to connect the bus.

[intvnut]

A modern drop in replacement RA-3-9600 RAM chip and AY-3-8914 PSG would be really useful too. Perhaps the RAM could be onboard with a drop in replacement CP1610? Might need a null passthrough for the RAM socket then to connect the bus.

 

The STIC side of that interface is non-trivial. But, I'm sure with some effort entirely doable. Not that I can let that distract me from finishing LTO Flash....