Re: about the plus4

On 04/19/2012 02:17 PM, Steve Gray wrote:

> 2. It does share peripherals and the bitmap graphics modes are mostly
> the same

Multicolor Bitmap is not quite the same as with the VIC-II. As a bonus 
TED got you more colors, a hardware cursor, hardware blinking and 
hardware reverse mode.


> 3. Sound is much like the VIC. Remember originally the TED series was a
> low-end machine to compete with the $99 Sinclair ZX-81.

I think the competitor was the ZX spectrum. Compared to the video and 
audio circuit of the spectrum, TED was still better.

In case you don't know it, sound in the spectrum is done with the CPU by 
flipping a single port bit. About the simplest sound hardware possible.


> In stead of making the TED perhaps commodore should have updated the VIC
> to 80 columns....

That would have meant a complete redesign of the memory controller and 
bus interface. Remember, the original VIC was only able to do 22 or so 
chars per line in color with the affordable memory back then. And even 
that was only possible since it had the extra 4 data lines for the color 
RAM.

To be able to get 40 chars per line in color from this memory speed with 
the VIC-II meant to add internal 40 x 12 memory for char pointers and 
color information and the famous badline per character row to grab fill 
that memory.

TED has only 8 bit to do everything, that meant 2 badlines per character 
row already. As a bonus you get more colors. If you need a second 
badline, why use only 16 colors, you have 8 Bits for attributes now.

The only way Commodore would have been able to get 80 chars per line 
would have been to double the memory access speed (with 150ns DRAM you 
can do a complete RAS/CAS-Cycle every 260ns) and since video and CPU are 
using the same bus alternatively, also double the CPU speed. Or 
implement page mode. Also you'd need a faster char ROM.



> Since most of the work is in the TED the machine is quite simple. With
> 60k+ free memory for BASIC it makes a nice system to learn programming
> on. I like the case and keyboard.

I have to say I prefer the C16 over the Plus/4. The Plus/4 keyboard 
never agreed with me and they get flaky with age. :(

  Gerrit


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