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Re: [MiNT] Re[2]: GEM boost




I wonder if my NeXT could run MiNT.  I've had it running Linux and I
also have a Mac OS emulator for it.  Running Atari software on the NeXT
would be slick, even if its only a 25Mhz 040, it should do ok.

Getting MiNT to run on an '040 NeXT would be a neat thing. That NeXT even had the same 56001 DSP as the Falcon (perhaps all of them did?).
I've always wanted to get hold of a black NeXT cube...

Considering the stock 030 can't do a bus access every clock cycle (not

Definitely not without support for burst mode, which isn't possible with a 16 bit bus.

that I know of anyway), Atari didn't have a reason not to interleave bus
cycles with video and DNS devices.   I wouldn't be surprised if the CPU
only gets 1/2 or 1/4 of the bus cycles.

This is asynchronous memory we're talking about here, and the CPU doesn't have a direct connection to it. But of course there is still a clock that decides when to do what while communicating with the memory. Anyway, I don't know what the total bandwidth to ST RAM might have been, but I'm pretty sure you could run video modes on the standard hardware that used up around 30 Mbyte/s. But that cut down the bandwidth available to the CPU rather significantly, IIRC.

So, the system wasn't nearly as simple as "just give the CPU some percentage of the bus", rather the CPU seemed to get whatever it could of what was left after video was satisfied. I believe there was some internal buffering so that two consecutive 16 bit accesses hitting in the same 32 bit word didn't both have to go all the way to RAM.

It's funny, though, that if that measly sub-10 Mbyte/s bandwidth is used to communicate with a reasonable graphics card, even the Falcon will feel really speedy. (Granted, you don't want to go blitting large
...

As long as your demos are 320x200 x4bpp, you only have about 32K per
...

I was talking about normal work above, not demos. That is, using the VDI running GEM programs, in for example 1024x768x32 bit mode. With a graphics card like the Eclipse/RageII, that is very speedy in spite of the 4 Mbyte/s bus on my AB040 machine. Of course, that's because of the graphics card having really fast memory itself, and hardware accelerated drawing.

--
| Why are these | johan@klockars.net
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| so hard to do | http://www.klockars.net
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