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FPGA64 on Minimig V1.1 board
http://minimig.net/viewtopic.php?f=6&t=46
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Author:  dwyloc [ Tue Apr 19, 2011 9:24 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

*bump*

I take it there is still no progress on a working releasable C64 core for the minimig?

Author:  espskog [ Wed Apr 20, 2011 10:19 am ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

Yes..big bump, indeed. A working C64 core which has IO to the SD card would be very good.

Author:  frenchshark [ Sat Apr 23, 2011 1:27 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

espskog wrote:
Yes..big bump, indeed. A working C64 core which has IO to the SD card would be very good.


I am not sure there is enough LUTs to implement a 1541 emulation along with the C64 core on the Minimig FPGA.
Currently, on the MCC, for the 1541, the 6502 takes 750 LUTs, the 6522s 600 LUTs and the drive mechanism 500 LUTs.
The complete C64 takes around 6000 LUTs. The Spartan 3S400 has around 8000 LUTs...
Moreover, you would need to use the 68000 to manage the D64 images in RAM. You cannot access the images directly from the SD-Card since the timing is very sensitive.

One day, if I have some time, I will do it...

Regards,

Frederic

Author:  AW72 [ Sat Apr 23, 2011 9:17 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

Maybe it would be possible, that at least one-filers in .prg format could run. Anyway, the most games on the C-64 are one-filers. They can be loaded completely in the memory at once and would not need drive-mechanism.

Author:  frenchshark [ Sat Apr 23, 2011 9:41 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

AW72 wrote:
Maybe it would be possible, that at least one-filers in .prg format could run. Anyway, the most games on the C-64 are one-filers. They can be loaded completely in the memory at once and would not need drive-mechanism.


Yes, one filer is really straight-forward. You still need to use the 68000 and share the SRAM between the 6502 and the 68k.
Basically, you patch the KERNAL to skip the memory test and wait for the BASIC to start (8 VBL interrupts), then you load the game into memory by directly writing it with the 68000 (beware of endianness !).
Important : the BASIC pointers EAL, VARTAB, ARYTAB and STREND have to be updated accordingly.
Then, with a bypass mechanism that you put on the PS/2 to C64 matrix emulation, you automatically type RUN + enter.

This is pretty much how the MCC loads the first file and starts it with some little differences :
- It is a softcore NIOS and not a 68000
- The keyboard PS/2 to C64 matrix is done in SW by the NIOS (not hardcoded in HDL), this way different keymaps can be managed and the RUN + enter is easy to implement.
- The PRG file is loaded from a D64 image that resides in SDRAM and not from a file on the SD-Card.

You can also have a pretty good drive emulation by porting the SD2IEC AVR code to the 68000.
But, this is a lot of work.

Regards,

Frederic

Author:  espskog [ Sun Apr 24, 2011 8:35 am ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

The current FPGA64 core uses the spare-io on the minimg to connect to a IEC device. We might use the same stuff on the FPGA Replay board (probably with some tweaking of the core) but at least we can load from a IEC device like the SD2IEC or the C64DTV-III unit. It's a good alternative and a IEC unit is small enough to fit inside any Mini ITX cabinet if you like. I testet the FPGA64 core for Boing4000 and used a couple of the spare-io pins on the minimig to ook up to a uIEC unit and it worked like a charm. :)

Author:  AW72 [ Mon Apr 25, 2011 10:24 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

frenchshark wrote:
You can also have a pretty good drive emulation by porting the SD2IEC AVR code to the 68000.
Frederic


Yes, i have two SD2IEC`s here. One on a C-64 and the second on my C-64DTV. The drive-emulation (d64-files) work not as perfect as on a 1541-Ultimate, but quite good. With some fast-loaders it has problems. I would say, from the games on d64`s, i tried on it until now, about 70% work. t64 and prg-files work 100% there.

What i really like on the SD2IEC is, that M2I-files work. This format can put many d64-disksides together to one file. No more disk-changing necessary in games with many disks. This is really a big advantage of this file-format. by the way, good M2I-side here: http://www.creepitz.de/downloads/m2i/
I hope that, in next firmwares, my 1541-Ultimate can also load M2I. Until now it can not.

Author:  gibs [ Sun Mar 29, 2015 7:37 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

Hello,

So no FPGA64 for Minimill 1.1 has been released ?

Author:  boing4000 [ Tue Mar 31, 2015 9:43 pm ]
Post subject:  Re: FPGA64 on Minimig V1.1 board

No release and no more work at the core by now.
Problem also is the timing of the FPGA64. It will not be possible to match 100% cpu speed to support 1541 speedloader, so only standart or single file load function works.

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