sony/news_68k_iop.cpp: Implement NWS-831 driver

[briceonk]

Let me know if any of this should be split out into a separate PR and I will do so.

Highlights:

• Working dual-processor system that can boot both NEWS-OS 2 and NEWS-OS 4
• Basic peripherals work (serial, SCSI, networking kinda)
• Lots of custom stuff that has been partially reverse-engineered like the front panel and the custom MMU

Lowlights:

• Networking stability is bad
• The amount of custom stuff means that this driver has a lot more educated guesses in it than the NEWS r3k, r4k, and single-processor 68k drivers do.
• NEWS-OS 4 installer uses unemulated tape drive commands, so the OS install process doesn't work right now. Instead, I used a script I wrote a while back to generate an image from the bitsavers dump of NEWS-OS 4.1C: https://github.com/briceonk/news-os/tree/master/src/news-inst
• The SCSI DMA setup is really hacky (just like the Macintosh stuff) because iopboot uses the features of the 68k that allow it to use narrower buses to do longword transactions

Front panel traced schematic:

[happppp]

As you can see, MAME doesn't have other brands of chips unless there are differences to emulate.
For example, see there's no HD68000 or TMP68000
Or for exact types, no MC68000P8 or MC68000P12

If you want to document exact brands/types of chips used, you could add hardware notes or a PCB diagram to the driver.

[briceonk]

As you can see, MAME doesn't have other brands of chips unless there are differences to emulate. For example, see there's no HD68000 or TMP68000 Or for exact types, no MC68000P8 or MC68000P12

If you want to document exact brands/types of chips used, you could add hardware notes or a PCB diagram to the driver.

Ha, guess I didn't see that :) Will remove those.

[briceonk]

As you can see, MAME doesn't have other brands of chips unless there are differences to emulate. For example, see there's no HD68000 or TMP68000 Or for exact types, no MC68000P8 or MC68000P12

If you want to document exact brands/types of chips used, you could add hardware notes or a PCB diagram to the driver.

Should be fixed now.

[briceonk]

I figured out the cause of the monitor ROM hang after I synchronized with master and fixed it, so I will work on your code review feedback next. Thanks for the review! :)

[briceonk]

I will address the remaining comments this week. Didn't have a chance to get to all of them this weekend.

[briceonk]

@cuavas @pmackinlay I think I resolved all of the feedback, so this should be ready for re-review.