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Offline FrenchShark

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Re: minimig 4000
« on: November 23, 2007, 04:28:00 PM »
Let's call it Maximig :-)

Seriously, my remarks:

- 2GB of Chip RAM will break compatibility, the Amiga architecture is limited to 8 MB of Chip RAM due to the memory map.
- To limit the the number of I/Os on the FPGA you can use the 040/060 in multiplexed bus mode (32 wires for address and data instead of 64).
- A coldifre is less expensive than a 040/060 and you can achieve a 100% accurate emulation (not the illegal instruction hack) with an average of 20 CPU cycles per instructions.
- A drop-in replacement of an A4000 board will be very expensive because of the board size, most of the PCB will be empty since the FPGA can integrate most of the A4000 components.
- Using a off-the-shelf evaluation board is less expensive: Altera is selling its NiosII evaluation kit WITHOUT the software for $395. The Altera FAE told me that the new Cyclone III NiosII evaluation kit should be available for December. It should integrate a VGA output. The price is still $395.
 

Offline FrenchShark

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Re: minimig 4000
« Reply #1 on: November 23, 2007, 05:25:28 PM »
Quote

A6000 wrote:
Quote

FrenchShark wrote:
- 2GB of Chip RAM will break compatibility, the Amiga architecture is limited to 8 MB of Chip RAM due to the memory map.


It should not break compatibility, the zorro III bus can have 1.75GB of fast ram, the 2GB ram would be used as fast ram with DMA and a smaller block of this ram is used for graphics and sound, whether that is limited to 2MB, 8MB, or more remains to be seen.


Most of the games expect the Chip RAM to be located at 0x00000000. According to the memory map 10MB are available from 0x00000000 to 0x009FFFFF. So a max of 8MB of Chip RAM can be used (managing the remaining 2MB with the chipset will be a pain).
 

Offline FrenchShark

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Re: minimig 4000
« Reply #2 on: November 23, 2007, 05:29:10 PM »
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alexh wrote:

Yeah right... NOT!

Emulation is good in a closed environment, as soon as you introduce external inputs, interrupts, exceptions etc. the house of cards comes tumbling down.

If it was possible and the speed was anywhere near a 50MHz 060 we'd have Dragon(?) boards by now.


According to my tests, the speed is near a 25MHz 040.
Maybe Elbox dropped the project or they are busy re-writing the KickStart with coldfire code.
 

Offline FrenchShark

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Re: minimig 4000
« Reply #3 on: November 23, 2007, 10:48:34 PM »
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Donar wrote:
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According to my tests, the speed is near a 25MHz 040.

Out of interest, which Coldfire and 68k emulator do you use? And what code did you use for testing?


The coldfire : the fastest (MCF548x) : 400 MIPS.
The emulator : my own emulator, it has to run from the internal SRAM of the coldfire. It uses self-modifying code.
 

Offline FrenchShark

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Re: minimig 4000
« Reply #4 on: November 24, 2007, 01:12:56 AM »
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Donar wrote:

Did you try if it is faster on 68060 optimized code than on average 68k code? From my understanding 060 optimised means less non implemented instructions, so the emulation only would be some kind of "pass through" for these instructions maybe giving more speed.


It does not change anything, EVERY instructions are emulated by the emulator. The only impact on the emulator is the use of simple addressing mode vs. complex addressing mode.