More Chipram

[Piru]

@KThunder

would a bus snoop chip that watches for accesses above the 2meg and inhibit action in the blitter et.al. prevent this?

Can't see how it could, and even if it could, it would lack the actual blit operation that is expected to be performed.

And it's not just blitter, it's all custom hardware DMA, copper, blitter, bitplane DMA, Paula audio, floppy read/write etc etc.

[Karlos]

@leirbag

I really don't mean to sound harsh here but you just need to accept it. There are people here who have forgotten more about the amiga hardware than you, or I, will ever know. And you are the only person insisting this idea will work.

The thing is, even if I can add 8MB an amiga's Z2 area by hacking away merrily, there are only 21 working address lines gluing it together. 2^21 = 2097152, which oddly enough is 2MB worth of address space. Even if I used lots of really fine wire to add the other 2 I would need to get to 2^23 (8MB), where do I connect them to?

Answers on a postcard...

[KThunder]

Piru wrote:
Can't see how it could, and even if it could, it would lack the actual blit operation that is expected to be performed.

And it's not just blitter, it's all custom hardware DMA, copper, blitter, bitplane DMA, Paula audio, floppy read/write etc etc.

what i meant was the memory not the blitter etc. if the snoop chip saw a memory access to say a memory location above 2meg, that would cause problems because of the partial decoding of the bus but the custom chips, it would basically step in and let the custom chips know not to do anything.

[Piru]

@KThunder

it would basically step in and let the custom chips know not to do anything.

Yes, I got the idea, and I tried to say that even if it could stop the operation, it would still lack it, which in itself that can be fatal aswell. Various examples: Missing write to a floppy. Not reading data from the floppy to memory. Not decoding floppy MFM buffer properly.

[KThunder]

you could easily allow normal operations to continue. anything under 2megs.

[Piru]

@KThunder

you could easily allow normal operations to continue. anything under 2megs.

And anything above it would break.

AmigaOS doesn't check from which address it gets the memory from. If you would make above 2MB "chip memory" available to system, it would use it, and break.

[KThunder]

the os doesnt break under winuae

[Piru]

@KThunder

the os doesnt break under winuae

Because the WinUAE emulates chipset that works with > 2MB chip memory. WinUAE's custom chips don't ignore the uppers bits of 0x274000 pointer, but use 0x274000 as expected.

See?

[stopthegop]

@Leirbag:

Critics are a dime a dozen.  This is not impossible.  I'm thinking again about one possible solution that came to me back when I was in AT school in the Navy. I never got past sketches for it, but I believed then (as I do now) that this is not the Mission Im possible some here make it out to be.  A lot of people are just dead certain about this and have intractably closed their minds to any possibility of nuance.      

[KThunder]

Piru wrote:
@KThunder

the os doesnt break under winuae

Because the WinUAE emulates chipset that works with > 2MB chip memory. WinUAE's custom chips don't ignore the uppers bits of 0x274000 pointer, but use 0x274000 as expected.

See?

thats what im saying piru.
 you use a bus snoop chip to decode the upper bits and if anything over 2meg is being accessed it lets the custom chips know

[Piru]

@KThunder

you use a bus snoop chip do decode the uppeer bits and if anything over 2meg is being accessed it lets the custom chips know

And tell custom chips to do what? Don't do the operation? If they don't, the result is garbage, regardless.

Do or don't, the result is the same. Something is trashed.

[Karlos]

@Stopthegop

Look, nobody said that an 8MB chipram capable hardware amiga is impossible per se. You could do it just fine if:

1) You make a replacement chipset capable of accessing the full 8MB
2) rewire entire motherboard to take said chipset, included but not limited to adding extra addressing lines etc
3) Make a patch for the OS so that the 8MB are recognised
4) Find a fix for whatever problems stealing the address space away from other hardware that wants to reside there causes.

If you do all of this, you will find you have essentially replaced the entire system. It wouldn't exactly be an expansion, it would be an entirely new system.

Hmm, guess what WinUAE does...

Something like MiniMig has the potential for this type of thing, but as far as existing classics systems go, forget it. However, if you can find a way to make the existing custom chips sprout more address lines and be able to use them then I will stand corrected on the original point.

[Karlos]

KThunder wrote:

you use a bus snoop chip to decode the upper bits and if anything over 2meg is being accessed it lets the custom chips know

So you get a system with >2MB chipram that can't be used by the custom chips. It also means that things that are supposed to get done, arent, which probably means a crash. How is this useful?

[KThunder]

Piru wrote:
And tell custom chips to do what? Don't do the operation? If they don't, the result is garbage, regardless.

Do or don't, the result is the same. Something is trashed.

yes exactly if you are trying to use above 2meg as ram you dont want the custom chips to do anything right, you want them to share the bus with the cpu. you dont need the custom chips to do anything with above 2meg do you you just want to use the ram for the cpu for programs

[KThunder]

Karlos wrote:
So you get a system with >2MB chipram that can't be used by the custom chips. It also means that things that are supposed to get done, arent, which probably means a crash. How is this useful?

noone ever said not let the custom chips do aything. everything under 2meg would be left alone by the bus snoop chip so the custom chips would continue to do their job

[Piru]

@KThunder

yes exactly if you are trying to use above 2meg as ram you dont want the custom chips to do anything right, you want them to share the bus with the cpu. you dont need the custom chips to do anything with above 2meg do you you just want to use the ram for the cpu for programs

And this is: fast memory.

So what's the point in trying to make it chip memory, again?