Posted By
MMS
on 2020-03-29
15:36:10
 |  Re: Sidekick264 - software defined cartridge
Sorry to not react to this topic earlier, as the whole project sounds great and very very exciting.
I had some nice impressions about few projects baced on PI beforehand (like 1541 emulator), this level of integration and communication is beyond my imagination.
Once I saw a YT video about a BBC Micro using the PI as a cooprocessor, I though wow, but the BBC Micro had such a cooprocessor slot by default.
C='s Sound Expander FM card emulation is especially a sweet spot for me. Yamaha FM chipset has low added value for a C64 (and customers really did not understand why C= released it--> very few sold), but it could have been a great add-on by Commodore to one of the most critised part of the 264 (sound).
Now check out the color of the FM cartridge (black, together with the IEEE interface and digitizer) and the Ext.Audio pin on the 264 expansion port: I mean the 264 project team could originally seems to have an idea to use an external audio card...
(I suppose after the failure of the 264 series on the market all HW and SW projects quickly stopped to prevent further losses for Commodore).
The SW realized SIDs (especially dual SID) is a great idea, especially at the times SID chips started to cost my kidney 
The flexibility of the project sounds great.
Using it as an external cooprocessor? Wow. I saw George's fantastic 3D routine, and the main blocking point was the slow floating point 5 byte arithmetic of the 8501. The 8087 FPU of the 8086 made the 3D rendering 5x gfster, and even the 8086 was not so bad. Imagine a much faster gfx, or even able to do most of the tricks inat the border, like SW-sprite. Such an external FPU/GPU like expansion unit could make all the 264 gfx shine.
Ideas?
-Maybe mapping the PC mouse to the Plus/4? Could be mapped as an 1351 mouse, same address as NST's SID card using.
Although I was thinking a little on that (how to optimize BSZGG's code) and maybe 1 byte precision for the X coordinates could be enough for the 264 series (160 positions), it would be 1 pixel step in multicolor, and 2 pixel step in HIRES.
Actually the RS232 mouse is available only for the +4 only due to user port, while this card would make the mouse more available (not only for +4), not to mention the current price of the 1351 mouse (but real RS232 mouses became really expensive too).
I remember how easy was to work with PC Norton Commander when used the character screen mouse, or programming with Plus4emu.
Few comments:
The GeoRAM was a cheaper method to provide big enough memory for GEOS users without the extra price or REU.
Yes, with NeoRAM it could be extended to 2MB, that sounds great.
On the other hand, GeoRAM told to be a kind of slower approach without MMU, and the small 256 bytes long blocks seems to be a little weird for me, though it is told to be easy to program.
http://www.cbmhardware.de/show.php?r=1&id=4/Georam
Does it have any benefits VS the Hannes RAM expansion unit?
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