Posted By
Claude
on 2019-02-06
03:58:32
|  Re: Possible Plus4 successor
@Frederick:
I want to be independent from specific boards for two reason. At first these boards include functionality which is not needed but for which you pay. My optimal solution would be just a single chip (SoC would be nice), external memory and all required cards for peripheral connectors. The second reason is not so obvious. Most SoC are not complete documented (exceptions are the PIC32 boards from Olimex and to a greater extend Raspberri Pi). Writing an optimizing machine-code translator require bare-metal knowledge of all relevant functionality, including the integrated GPU. For the same reason it makes no sense to me to base this program on an operating system like Linux and all proprietary binary blobs which would only complicate the implementation and cost run-time performance. This is important because simulating video output to a frame buffer can result in some latency already. For most emulators I know this is not visible, anyhow you will recognize this at some point as the C64 mini shows. To be said raw emulation does not help either in this respect. An AOT compiler (not JiT which also depend on interpretation) have the advantage to detect common access patterns to video memory as part of code generation. This can be exploited to generate optimized native code in these cases. This way the latency problem is in most cases avoidable (the exception are dynamic generated code sequences with graphic output).
In regard to the mentioned boards and chips:
I think the Propeller II would be ideal. Anyhow I can't see to get one soon and the long time support from Parallax is in my opinion somewhat questionable. Sadly I found also the TI DSP somewhat unaccessible (well, it seems there customers are mainly large companies) so I changed my opinion and will use a PIC32mx DA instead (which includes a complete documented 2D GPU, a very capable DSP, USB controller, 512 KByte internal RAM, 2 MByte Flash memory and cost under 8 Euro). For this chip exist an Olimex board so I can start with the implementation beside board design which is nice.
|
