Ah, the Commodores that should never have been. Ironic really, since I may not have been here at this PC if it hadn't been for the C16.
In 1983, Commodore were doing extremely well with their well specified but expensive Commodore 64, but they were loosing out in the budget computer market. The 5K Vic 20 was looking dated with its 20 column display and 8 colour palette, and here in England at least, its "real keyboard" wasn't enough of an advantage to persuade potential buyers away from the 48k Sinclair Spectrum that all of their friends had bought.
Having decided that integration was the key to lowering costs, the 'TED 8360' chip was created to power the new generation of 264 series computers, providing graphics, sound and I/O control in a single chip.
VIC-II style sprite graphics were out, as was the popular SID chip, but in came a 121 colour palette, a new improved version of BASIC, a built-in assembler and machine code monitor and for the first time a parallel disc drive interface in addition to the standard Commodore serial interface.
The MOS 7501 CPU was selected to drive the TED chip, and ran at 1.1Mhz
So, this new chipset was placed into a tiny case along with a Spectrum-like rubber membrane keyboard with 16k of RAM and the Commodore 116 was born, but completely failed to sell. Presumably, because it wasn't compatible with the huge C64 software library and it had a horrible keyboard. If people wanted a horrible keyboard and didn't care about C64 compatability, they would (and did) buy ZX Spectrums instead.
Now, at this point, Commodore spotted a couple of issues that would probably have been glaringly obvious to any other company before going into production.
First, Why use a new case and membrane keyboard when you've already got a factory tooled up to produce almost identical VIC 20 and Commodore 64 cases and keyboards? Take a C64 case design, modify the holes in the back and order the case in dark brown and the keys in ivory, and you've got the makings of a Commodore 16. The C16 was moderately successful, and was the computer that my Grandad bought "for the grandkids to play with"
The second minor problem of course, was that the 264 was in a lot of ways more powerful than the C64. The 10% faster CPU, improved colour palette and parallel disk interface meant that although it lacked the hardware to compete with the C64 in the games market, it was perhaps better suited to education and business markets.
With this in mind, Commodore set about designing the Plus/4. Once again, they scrapped the VIC 20 case and went for a more compact design, but this time they used a regular keyboard in place of the 116's membrane. The on-board RAM was upped to 64kb and to further demonstrate that this was no games machine, Commodore included office software in ROM in the shape of "4-in-1", possibly the world's worst word processor, spreadsheet, graphing tool and database.
The Plus/4 sold OK as well in the end and still has a loyal fan-base, but there were never as many around as C64s. There just wasn't a large enough market for two computers so similar, and the C64 had already had a head start in terms of software availability.
stupot asks: "How the heck do you get a 121 colour palette? I can't figure it out..."
Well, technically you could be lead to believe that it's 128 colours, since it's 16 colours, each of which has 8 shades. However, one of the colours, black, looks exactly the same whichever shade you specify, hence (15x8)+1 colours.
asks: "Ok... next question... how do you get 16 colours to have 8 shades of? Are there 2 bits of one component, plus 1 bit each of the others? This sounds like a very odd system indeed!
It's more simple than it sounds. The sixteen base colours were predefined, ie. black, white, red, green, light green (Yes, as a separete base colour). The Commodore 64 used a similar set of predefined colours, but for reasons known only to Commodore, they are different.
Now, for each of those base colours you could specify a shade value, which adjusted either the brightness or the saturation of the colour. I don't remember which, but I'll find out!