Posted By
MMS
on 2022-10-16
18:17:08
 |  Re: C16 JUGGLER board is under development.....
you know I like your upgrades. :-) Due to the ESD protector and the two remaining non-operating Plus/4 I own I am interested too.
Just a curious question I raised previously in a PM:
if this is not a real 6502 CPU, and the CPU is just the slave of the TED, during the periods the CPU works alone on the borders, there is no way to make to add to the package a switchable CPU FRQ doubler or more? If the "CPU" can manage such speeds.
It would not make the project much more expensive, on the ebay it is close to 1€/pc
https://swharden.com/blog/2016-08-31-ics501-simple-frequency-multiplier/
AFAIK noone ever made a CPU upgrade option for the Plus/4, while other 8 bits had it.
It could be the first on this platform, and could provide really something new:
-C64 had the 4MHz external 6502 and the CMD 20MHz SuperCPU
(Ruud Baltissen developed an internal replacement with 65816 CPU with potential 16MB mem, but did not offer speed increase http://www.baltissen.org/newhtm/02to816.htm)
-BBC Micro had the CPU cards with different, fast CPUs (including (Z80 and 6502 @4Mhz)
-C128 had the integrated Z80, though it was pretty slow, in practice only 1MHz  , but 7502 could be switched to 2MHz
-Atari 800XL has 6809 upgrade, but no programs made to use it.
While the SuperCPU and the C128 Z80 required special programming, in this case nothing to be added, and it comes from the special architecture the 264 series has:
the CPU simply would work faster on the border, than normal (instead of the 1.76MHz the 2x means 3.5MHz or maybe the 5x 8.8 MHz).
I mean if a higher than 1MHz comes from the TED, it would be doubled, 5x or so.
In this way it would not influence the picture, sound or sync or any other things, as handled by the TED on his own frequency.
Different CPU speeds is a huge problem on other platforms (due to video and sound issues), but (I think) it is not a big issue in our case.
How it could be used on our platform?
-Better quality digi SID emulation by higher sampling rate.
-More time for proper (and more) soft-sprites
-4 channel 4bit digi tracker as seen on ZX Spectrum with their 3.5MHz CPU (3.5MHz with 6502 code would be more than enough).
https://www.youtube.com/watch?v=g_Ox3fSCSEw
-Better decompression times
I hope you see my point and the potentials of it... If the slewed down CPU in the TED periods would not cause a problem.
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