Re: Crosspost: Did the cpu influence the display?

["Bill Plenge" <B_Plenge@NoSpam.com>]

Bill H wrote:
> Peter van Merkerk wrote:
>> Bill H wrote:
>>> ===========================================================
>>> This message has been cross-posted to a number of revalent usenet
>>> groups, so please do not start a "My system is better than your
>>> system flame war".
>>> ===========================================================
>>>
>>> Relying on my memory and a cursory check on a number of websites it
>>> appears that the majority of Z80 cpu based computers had black and
>>> white displays, where as the majority of 65xx computers had a color
>>> display.
>>
>> I don't think that is true, at least not for home computers.
>>
>> There are plenty of (early) 6502 based system which supported only
>> B/W display, and there are also plenty of Z80 systems which
>> supported color (ZX Spectrum, MSX, Amstrad CPC, Sharp MZ series,
>> Enterprise...etc).
>>
>> If we include CP/M computers (which are Z80 based) then what you are
>> saying might be true. However those where intended for business use.
>> In those days color was not deemed to be important for business
>> computers.
>>
>
> I probably should have specified a time period. I was thinking more of
> the 78 - 82 time period and computers that were available for home use
> mainly in the US (only because that is where I am and have the most
> experience with). During that time period the popular computers on the
> Z80 side where the Tandy's (and clones), the zx81, ts1000 and some
> CP/M machines. On the 65xx side where the Apple ][s, Atari's and
> Commodores.
>

Given that time period I think you'll find the major reason being the cost 
of RAM (circa '78 16K was about $80, by '82 64K-128K could be had for the 
same price) and color monitors at the time.  Combine that with the general 
publics attitude that home computers were just a fad and you can see the 
resistance a company would have designing a color system for general use in 
those early years.

>>> Now there are exceptions to this, but it makes me wonder, did the
>>> CPU influence the display?
>>
>> There is no technical reason for having a correlation between color
>> support and the CPU.
>>
>>> Is there an inherent reason why most Z80 computers had b/w displays
>>> and 65xx computers had color?
>>
>> I don't think that statement is true, so the answer is no.
>>
>>> You may think it would have been cost, b&w would be cheaper than
>>> color, but in the majority Z80 computers where more expensive than
>>> 65xx computers.
>>
>> I doubt that is true either. For example the Sinclair ZX Spectrum was
>> significantly cheaper than most 6502 based systems, and did support
>> color.
>>
>>> Now it could have been display size, many Z80 computers used 80
>>> columns which is hard to achieve when using a TV as a monitor. But
>>> on the other hand, with color you need more memory to achieve a
>>> good working resolution.
>>
>> See my remark at the beginning.
>>
>>> So the question is, did the cpu influence the display?
>>
>> No, at least not whether the system supported color or not. Of cource
>> the CPU is one, but not the only, factor that affects how fast a
>> display can be updated, but that is another story.
>
> One reason I was thinking that the cpu could influence the display is
> that z80 had a larger instruction set that allowed you to do more with
> the cpu than the 65xx. So on the 65xx side you needed more support
> chips to do things that the cpu could not.
>
> For example on a 65xx would it be possible to drive the display as is
> done on the zx80 (not the ts1000 or zx81 which used a custom chip) and
> the cpu with only a few off the shelf logic chips?