MiniMig with AGA

[FrenchShark]

I doubt softcores are going to implement any cache anyway. They just rely on the brute execution power, faster memory etc.

I have a TG68 softcore with a 4-way 8KB unified cache running on an FPGA.
What's wrong with that ?
To use the massive throughput of an SDRAM, you have to put a cache.
Pure random access on an SDRAM is not better than an old DRAM : 60ns at best.

Regards,

Frederic

[FrenchShark]

So I assume the 68000 softcore has some kind of built-in cache to compensate for the slow memory interface, too?

The softcore from Tobias does not have a built-in cache but I added one. This is the beauty of VHDL.
The cache is more like a L2 than a L1 one (no instruction prefetch, no Harvard architecture). It works in write back mode too.

Regards,

Frederic

[FrenchShark]

@ MikeJ or Yaqube,

Can you please tell us the sysinfo speeds from the FPGAARCADE board ?
I realy want to now how fast the softcore speeds are and HDF speeds.

On http://www.a1k.org, Tobias has his new core having 6 MIPS with a 8-byte I-Cache and 7.6 MIPS with 16-byte I-Cache. This is with his new core.
You can expect maximum 6-7 MIPS with the first TG68 version running at 28MHz and a good cache.
The new core would certainly reach 15 MIPS.

Regards,

Frederic

[FrenchShark]

TG68K @ 7.09 MHz : 4.27 x A500 / 1.85 x A1200
TG68K.C @ 7.09 MHz : 5.81 x A500 / 2.52 x A1200

Why just 7MHz ? Is it because of the non cached SDRAM access ? (7MHz for the CPU, 7 MHz for the Chipset, 70ns access time).
Looking at the numbers, the new TG68K.C execute almost one instruction per clock : it is at the performance level of a '040 !
Tobias claims it can run at 40MHz on the fastest (and more expensive) cyclone II.

Hardfile read speed: 1900-2000 KB/s

Is it with SPI or 4-bit SDIO ? Is DMA involved ?

[FrenchShark]

Autofire generally uses a 555 timer. I'm not sure what joysticks you've taken apart, but they don't sound great. Unless the auto fire toggles on and off then it isn't auto fire & you can't do that with just a switch.
 
555's work best with higher voltages, so it might get upset with 3.3v
If might work, you'll have to test it.

We do not need joysticks with autofire anymore.
A variable speed autofire can be integrated in the Minimig core.

Regards,

Frederic

[FrenchShark]

Nope it's not faster then a 030 50Mhz.

The softcore speeds are:

TG68K @ 7.09 MHz : 4.27 x A500 / 1.85 x A1200
TG68K.C @ 7.09 MHz : 5.81 x A500 / 2.52 x A1200

Hello,

where did you get those numbers ? From Tobias on A1k.org ?
The TG68 seems to be twice faster than the MC68000. I had to slow it down to 3.5 MHz to make Battle Squadron runs with no graphics bugs.
But, I still get Turrican II main screen animation running too fast. Maybe, I have to go down to 1.75 MHz :-).

Regards,

Frederic

[FrenchShark]

I have seen the board in Essen. The PCB is very small.
The Minimig core runs great and the Kickstart thinks it is a 020 @ 14 MHz.
Good job !
I also have a nice talk with Jakub about possible optimization.
Mike can you make one with an Altera FPGA ? I do not like Xilinx tool and neither Jakub :-).
BTW, Quartus II Web edition 10.0 is out and it finally runs on Linux !

Frederic