Of FPGAs and the way forward

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@SamuraiCrow,

I'm not sure if I follow your thinking here. The FPGA issues aside, since they have been covered by AlexH... I don't uderstand your left brain/right brain metaphore...

Lets look at my aged Althon64 PC (and contrast it with my one of my A1200s with 4meg FastRam)...

The Athlon: It has a CPU on a bus with some memory, local and for the CPU only.
The A1200: It has a CPU on a bus with some memory, local and for the CPU only.

The Athlon: It has a separate main System bus for all support systems (GFX, Audio, I/O).
The A1200: It has a separate main System bus for all support systems (GFX, Audio, I/O).

The Athlon: It has a GFX CoProcessor (a Nvidia 8600) with it'a own RAM (512Megs) that performs all gfx functions, and capible of massively parallel GP processing.
The 1200: It has a GFX CoProcessor (The Blitter, Copper and barrel shifter) with its own RAM (well shared with the Audio and I/O).

The Athlon: It has a dedicated Audio DSP and its own RAM.
The A1200: It has a DMA fed DAC, and RAM shared with the GFX and I/O

I could go on... but my point is made, the Athlon is structurally rather similar to the A1200, but massively improved on the idea. Each of the various subsystems are powerful independant devices in their own right. I don't really see how this relates at all to your mataphore?

[bloodline]

SamuraiCrow wrote:

@bloodline
The right-brain analogy was for the custom chips having their own memory bus.  

Well, all systems use separate busses for different parts of the system... that's nothing unique to the Amiga.

On the NatAmi there are 16-megs of Chip RAM built in to the FPGA.  

Is that an FPGA with 16megs?

It is used as local-store memory for the custom chips and functions like a software cache for multimedia chip accesses.

I don't understand... software cache?

Oddly, for whatever reason, the custom chips on the Natami can access the Fast bus and gain a huge amount of memory.  So whether it's fully a dual-bus Amiga remains to be seen.

Again, I don't understand... if the Custom chips can access the CPU local bus, then why bother with it?

Your analogy of the PC being like an Amiga holds very true.  Many graphics cards do have their own memory and are like Amigas in that aspect.  If the GPU were used for doing all of the sound mixing like is proposed on the NatAmi, your AROS system could be an Amiga.

Why not just use a DSP for the Audio mixing? Leave the GPU to do GFX stuff... perhaps?

[bloodline]

Downx, perhaps if you sort out your quotes I'd be able to follow it...

I honestly have no idea what you are talking about... I think you've misread my post...  since I know you're not stupid... so reread it, cheers :-)

Oh, and yeah, I actually have a DSP in my Athlon desktop (with a Gigabyte Nvidia4 chipset)... and since I was comparing MY Athlon with MY A1200..

PS have you read the old AMD Athon64 technical docs right?

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-D- wrote:

downix wrote:

The Athlon ... Is limited to an 8-bit DMA system.

:-o

I can only think he is referring to the old southbridge DMA... I guess he doesn't know that it's not used any more, since DMA is an old concept... with USB, FIrewire and PCI-E

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SyrTran wrote:

bloodline wrote:
I can only think he is referring to the old southbridge DMA... I guess he doesn't know that it's not used any more, since DMA is an old concept... with USB, FIrewire and PCI-E

Wow.  just Wow.

I hope you didn't mean that the way you typed it.

Ok, I will have to go into detail then... (Can't anyone on this board use Google?)

I should probably let Nate answer this himself, as I'll probably get it as wrong as you did.  Yes, DMA is old.  It's as old as the IBM System 360, and it's as old as the Nvidia GTX 280.

DMA stands for Direct Memory Access.  It's not (just) a theoretical concept, or an antique type of data bus, it's a data transfer method, regardless of bus.  It's the method a peripheral device uses to put/get its data into/from memory without getting permission from the CPU.  It's written into the PCI/AGP/PCI-e specs.

An nVidia SLI setup uses DMA.  It doesn't wait for the CPU to fill its (3-way) 3 Gigabytes of texture/data RAM, the CPU tells the GPU where in main memory the data is, and the GPU goes and gets it, itself.  If you have a network connector, it will also DMA its data, as will any SCSI, and most SATA and PATA controllers (hint: UDMA mode).

BTW, Firewire, aka IEEE-1394, aka Sony iLink, also uses DMA.

DMA is also the reason there's a patch for A1-XEs.  If the OS isn't critically careful, the peripheral DMA data can get overwritten by the CPU - while the DMA transfer is still in progress.

When you refer to DMA on the IBM-PC compatible architecture you are refering to the old 16bit ISA system, the DMA in this part of the system can only access the lower 16megs of the adderss space. Almost nothing uses this any more... but it is all still included in the southbridge... this is where things like Serial ports, Parallel port, the Floppy drive, Real time clock, Legacy IDE, PS/2 ports and god knows what else antiquated hardware sits.

All modern parts of the system, GFX cards, Sound cards, I/O (USB, Firewire, ATA/S-ATA, Ethernet, etc...) sit on the PCI/PCI-E bus. Which is then connected via the northbridge to the CPU. The CPU has a second local bus where the main system RAM is located... I hope Downx wasn;t suggesting that the System RAM was located on the PCI/PCI-E bus because that would be a pretty horrific architecture. The Athlon64 is slightly different at the top as it use HyperTransport, and my particular Athlon64 actually has three Hyper transport links and its own RAM controler... but that just confuses this issue.

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@Downx

Are you smoking crack? My mouse and Keyboard are on USB, which itself is on the PCI-E bus, which is connected to the CPU via HyperTransport... the RAM is connected directly to the CPU, not via an HT link.

Your idea of a computer system seems 15 years old!!!! The only thing on the south bridge is pretty much just the BIOS now (since I don't use any of the legacy ports or floppy disk)...

Start here to refresh your memory:

http://en.wikipedia.org/wiki/Hyper_transport
http://en.wikipedia.org/wiki/Socket_939


And here is a nice picture of the standard PC architecture (Note the different Busses):

[bloodline]

downix wrote:

bloodline wrote:
@Downx

Are you smoking crack? My mouse and Keyboard are on USB, which itself is on the PCI-E bus, which is connected to the CPU via HyperTransport... the RAM is connected directly to the CPU, not via an HT link.

Your idea of a computer system seems 15 years old!!!! The only thing on the south bridge is pretty much just the BIOS now (since I don't use any of the legacy ports or floppy disk)...

Start here to refresh your memory:

http://en.wikipedia.org/wiki/Hyper_transport
http://en.wikipedia.org/wiki/Socket_939


And here is a nice picture of the standard PC architecture (Note the different Busses):

Um, dude, that is what I just said.  The "Northbridge" which includes the RAM controller is integrated onto the die with the CPU in the Athlon, with a HT bus connecting the CPU to the southbridge.

So you agree, for anything to utilize system RAM, it must go through the northbridge, now handily contained within the silicon of the Athlon CPU?  Or what are you saying?

Of course... and in that way, System RAM on a PC is like FastRAM on the Amiga. Which was my original point. Just as the Amiga Chipset does not access FastRAM, the Gfx chips and Audio chips do not access System RAM... like the Amiga there is RAM dedicated to the task.

That picture you have is several years old, only Intel still uses that architecture, and Intel is abandoning that next year with their next-generation interconnect technology.  Death to the Front Side Bus!

Given the two biggest PC architectures are AMD and Intel... and the biggest of those is Intel, then that picture is more than adequate!

Now if we refer back to your original post... You will agree that it bears no relation to the modern system.