[sdiy] New to list - and DSP development

[René Schmitz]

Hi Magnus, Rainer et al.,

> 1,8432 MHz = 96 x 19,2 kHz

Hmm, more like 115.2kHz * 16, higest rate generally used with RS232, and 
  the factor 16 because the UARTs use to oversample at that rate.

> When IBM created the IBM PC they did these choices. I guess they had the
> intention that graphical cards would easilly be able to be simplified by
> already operate synchronous with the NTSC colour-burst. I have only seen one
> graphical card able to output TV-signal, and then only in greyscale. Actually,
> that card was sitting in the spare-part built PC I run my first UNIX ever on,
> the SCO Xenix. It had a wooping 8 MHz 286 motherboard, a 20 MB HDD and a 360 kB
> FDD. I used the familly 26" TV for that one, using a SCART contact to get in
> there. It worked, but I never lifted with XENIX but kept dreaming about hacking
> a real OS like UNIX. Today I am very happy hacking away on Linux I might add.

I had a PC where there was a 24Mhz Xtal for the 8086 CPU (div 3 = 8Mhz) 
and a 28.636MHz clock for the video generation (CGA modes...)

(Infact you could hack it to use the video clock also for the CPU, to 
get a whopping 9.54MHz...)

>>>Most other units would also be able to handle this. It's a mystery why
>>>this was not included into the standard, or maybe it's not as much of a
>>>mystery :-P
>>
>>Interestingly, a number of internal buses of older machines run off
>>"double MIDI".
> 
> 
> Standards are good, everyone should have their own, but in reality everyone
> run multiple standards for themselfs.

My guess would be that they used whole number MHz clocks in those early 
MIDI synths, and they chose to run the UART from that too. And didn't 
need to be compatible with teletypes anyway.
The PC wasn't really a home machine back then. And homecomputers had 
often whole numbered multiples of 31.25k as clock frequencies, like 2, 
3.5 or 4MHz, often without dedicated serial interfaces.
Infact I have read that there was a game on the ZX Spectrum which could 
put out midi on the cassette port...
So at that time there wasn't the notion of an established standard.


Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159