Theory thread: How would you update C64?

[Gorf]

Originally Posted by ImmortalA1000

VDC is useless as it needs the EGA style monitor frequencies

The VDC is quite programmable frequency wise - it is not fixed to 20kHz EGA … but it has of course EGA-style voltage levels and digital colour-out.
But that could have been fixed quite easily with a resistance ladder …

So one nice possible improvement would have been to sync both frequencies (if the user wants it) and mix both signals (VIC-II and VDC) in a genlock-style fashion…
That would have given the C128 a dual play-field mode

[KONEY]

Fun fact: if you look at how much software and hardware is published today for C64 and Amiga you end up realizing we really live in an alternate timeline

[Gorf]

By the way: the VDC gets bashed a lot - but it is much more capable as most people think:

[ Show youtube player ]

[Cris1997XX]

Originally Posted by Tigerskunk

I think the C64 is great as it is. And in 1985, there was already the Amiga. So no room for a real C64 successor.

But if it was another timeline without the Amiga and ST: a C64 II with 256 kb, double SID and a 16 color palette that could be chosen from let's say 512 or 4096 colors, released in 1986, would have gone a long way, imo.

32 colors from a 512 overall palette would be a much bigger jump, honestly...almost like Atari ST games using raster effects

[ImmortalA1000]

Originally Posted by Gorf

The VDC is quite programmable frequency wise - it is not fixed to 20kHz EGA … but it has of course EGA-style voltage levels and digital colour-out.
But that could have been fixed quite easily with a resistance ladder …

So one nice possible improvement would have been to sync both frequencies (if the user wants it) and mix both signals (VIC-II and VDC) in a genlock-style fashion…
That would have given the C128 a dual play-field mode

The VDC was just something off the shelf Commodore had clogging up warehouse shelves. It's really two more or less mutually exclusive machines put onto a single motherboard and a decision is made early in the bootstrap process which 'machine' is going to take charge of the motherboard. Nothing about the C128 really made sense. Ideal option would be to have the Z80 and 8502 working in parallel and an 80 column chip that worked with RGB. That's how it should have been.

Still, it sold 4.5 million units based on the fact people believed it was a 2mhz 128k update to the C64 and waited patiently for those sort of impressive C128 exclusive games to turn up....which they never did

[Gorf]

Originally Posted by ImmortalA1000

The VDC was just something off the shelf Commodore had clogging up warehouse shelves.

sure - it was originally designed for the C900.
That fact alone does not make it a bad chip.
(the missing interrupt signal does, but that got fixed in later revisions)

It's really two more or less mutually exclusive machines put onto a single motherboard and a decision is made early in the bootstrap process which
'machine' is going to take charge of the motherboard.

It has its own RAM ... but so do all PC gfx-cards and also the gfx-chip of the Apple-IIgs
The problem was the requirement for an EGA-monitor - well at least for European customers, since in the US these monitors were rather cheap and easily available in comparison.

And as I said: this can be fixed - adapters exist. A sync-mode with overlay would have been quite easy to implement.
But Commodore desperately wanted to offer something more "business-like" ...

Nothing about the C128 really made sense.

something without the Z80 but still 128k of ram and possibly more speed would have been nice a year earlier instead of the 264 line
85 was a terrible timing and did cut into the Amiga sales ...

Ideal option would be to have the Z80 and 8502 working in parallel and an 80 column chip that worked with RGB. That's how it should have been. the >

no.
(the CBM-II line offered this, but virtually nobody was interested and they only sold about 20k units...)

[Cris1997XX]

Originally Posted by Gorf

something without the Z80 but still 128k of ram and possibly more speed would have been nice a year earlier instead of the 264 line
85 was a terrible timing and did cut into the Amiga sales ...

Dual-SID would've also been amazing, but that was more useful to music enthusiasts than anyone else

[Bruce Abbott]

Originally Posted by Gorf

By the way: the VDC gets bashed a lot - but it is much more capable as most people think:

[ Show youtube player ]

Interesting demo. The scrolling text at the end is very nice, except the scrolling is very jerky. The other parts appear to show significant limitations too, eg. a small graphics window for color images and only monochrome at full screen. maybe good for text adventures with small pictures, but not much else.

Originally Posted by ImmortalA1000

The VDC was just something off the shelf Commodore had clogging up warehouse shelves.

This is not quite right. The VIDC design was originally intended for the Z8000 based C900, but the VIDC chip used in the C128 was brand new.

The C128 inside story: Bil Herd

the very very very early concept of the C128 was based on the D128, a 6509 based creature (boo... hiss). The engineers on the project had tacked a VIC chip onto the otherwise monchrome (6845 based) in an effort to add some color to an otherwise drab machine. No one dreamed that C64 compatibility was possible so no one thought along those lines. I was just coming off of finishing the PLUS 4... I was not happy with the end result and had decided to make the next machine compatible with _something_ instead of yet another incompatible CBM machine... I was allowed/forced to put my money where my mouth was and I took over the C128 project.

I looked at the existing schematics once and then started with a new design
based on C64ness. The manager of the chip group approached me and said they had a color version of the 6845 if I was interested in using it it would definately be done in time having been worked on already for a year and a half...

Originally Posted by ImmortalA1000

It's really two more or less mutually exclusive machines put onto a single motherboard

The video circuitry yes. The CPU was the same, but when running at 2MHz it couldn't use the VIC because it was too slow. The VIDC used its own memory so this this wasn't problem, but like IBM CGA etc. it didn't interleave memory accesses so the CPU had to wait, dramatically slowing down rendering. In a text based system this wasn't too bad, and the VIDC also had a blitter which could scroll a whole screenfull of characters much faster than the CPU could do it.

The Z80 was another story, being an integration of the CP/M cartridge for the C64. In the C128 it was also used during initialization to set up the video display depending on which mode the machine would be running in. It was still possible to access the VIDC from C64 mode, so it was really just the VIC and VIDC that were mutually exclusive. Not much different from an Amiga with RTG card or a PC with CGA and MDA cards installed.

People think of the C128 as a C64 with 80 column text and Z80 thrown in, when it was really the opposite - the VIC and Z80 were the thrown in to provide C64 compatibility. This was a mistake, but less of a mistake than releasing the C128 without C64 compatibility.

What Commodore should have done was redesign the VIC to work at 2MHz so it could do 80 column text and graphics in a C64 compatible way. Combined with 128k RAM and a high performance floppy drive it would be a good update, like the A1200 was for the A500. If they used the same case design as the C65 it would be perfect!

[Gorf]

Originally Posted by Bruce Abbott

Interesting demo. The scrolling text at the end is very nice, except the scrolling is very jerky.

That must be because of emulation, capturing or or YouTube compression ... filmed from a CRT it is perfectly smooth:

[ Show youtube player ]

[ImmortalA1000]

I think it's fair to say I don't respect the C128 as a computer, my friend at University had one though and he loved it....even though he was playing the same games I was on my C64

The 128D is the Rolls Royce of systems to play C64 games on though today, which is why I have a brand new unused one in my collection. My fav' C64 compatible is the SX-64 but my favourite way of loading games, for nostalgic reasons, is from tape so that's no good to me. I prefer the SX-64 keyboard but the C128 has a nice keyboard no arguments there.

It just seems a waste of expensive hardware to not have a computer with the 2mhz 8502 and Z80 working in parallel via the VIC-II on a CRT TV that's all. Feels a bit thrown together as a design, As ever YMMV.

[TEG]

Originally Posted by ImmortalA1000

I think it's fair to say I don't respect the C128 as a computer, my friend at University had one though and he loved it....even though he was playing the same games I was on my C64

I had a C64 and then a C128 and I was in love with the latter too!

The 128 mode was for "serious" mood: programming with the nice Basic V7 (sounds, graphics and sprites instructions, 128K), eventually switching to 80 columns, hacking C64 games or programming the 8502 with the integrated assembler editor and editing sprites with the integrated sprites one! The C128 is underrated by whom did not use it because its nice ROM are masked by the shinning C64 mode for an external eye.

And of course there was the nice keyboard. Very important, especially because it was the first personal computer with a numeric keypad. Very handy to enter C64 hexadecimal listing found in magazines! French C128 had even an option to switch to Azerty keyboard.

+ the so nice design and the robust power supply.

When I had finished with the "serious" mood, I switched to the "games" mode, ie the the C64 mode which was 100% functional. So it was a very complete and lovely machine.

[eXeler0]

Originally Posted by ImmortalA1000

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Still, it sold 4.5 million units based on the fact people believed it was a 2mhz 128k update to the C64 and waited patiently for those sort of impressive C128 exclusive games to turn up....which they never did

The C128 was my first computer, got it at the end of 1985 and mostly I got it because a sales-dude hyped it up with stuff I eventually never used it for ((modem , 80 column display..) but also because most of my friends had C64 and I wanted something better and the C128 clearly looked cooler ;-)
But to be fair, when I didn't play C64 games (which was probably 90% use cases) I did use Basic 7.0 for writing basic programs and also used the built in Sprite editor for use in programs.

[ImmortalA1000]

BASIC Lightning, which Ocean bought the license for and released as Laser BASIC and commissioned a compiler for it, was a really advanced BASIC. It was £14.99 and more advanced than the Research Machines Nimbus PC's BASIC and Acorn's BBC BASIC from what I remember.

One thing I totally forgot about was, and was not included in the spec of the C65, is the addition of a Sine waveform oscillator for the SID chip. Triangle is OK but you waste the filters rounding off the sharp peaks to simulate Sine waves and it's the most notable thing the SID didn't have that commercial analogue synthesizers did have even in the late 70s. Would break compatibility though due to the register locations assigned to the SID in the memory map.

[Gorf]

Originally Posted by ImmortalA1000

One thing I totally forgot about was, and was not included in the spec of the C65, is the addition of a Sine waveform oscillator for the SID chip. Triangle is OK but you waste the filters rounding off the sharp peaks to simulate Sine waves and it's the most notable thing the SID didn't have that commercial analogue synthesizers did have even in the late 70s. Would break compatibility though due to the register locations assigned to the SID in the memory map.

I wonder how this could be implemented in a cheap and non-bulky way.
Analog synthesizers would have a dial connected to a potentiometer ... one could also use a varying capacity instead (that is how a Theremin) works.

All you need are some 555s and a spoon:
[ Show youtube player ]

But seriously:

If you modify the SID to include a sine wave gen, then you would probably not stop there, but end up with something like AMY or of course the Ensoniq chip...

[redblade]

Atari Lynx in computer form?

But would have to be mass produced for cheap to flood developing countries