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Author Topic: 8 Mb CHIP RAM on All Amigas  (Read 19676 times)

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Offline motorollin

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #74 from previous page: June 04, 2006, 11:00:27 AM »
I'm starting to think this thread is a wind-up :lol:

@leirbag
Please, please prove us all wrong by re-designing the custom chips, rewriting kickstart and extensively modifying an A4000 motherboard. When I see the board, and watch the machine boot with no startup sequence and report 8MB of chip RAM, then I will believe it is possible :roll:

--
moto
Code: [Select]
10  IT\'S THE FINAL COUNTDOWN
20  FOR C = 1 TO 2
30     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NAAAA
40     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NA-NA-NAAAAA
50  NEXT C
60  NA-NA-NAAAA
70  NA-NA NA-NA-NA-NA-NAAAA NAAA-NAAAAAAAAAAA
80  GOTO 10
 

Offline thewalrus

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #75 on: June 04, 2006, 11:18:09 AM »
With regard to 2 MB chip ram I run out of chip memory when trying you open large graphic files or pictures even when opening files on a graphics card. Any way around this?
 

Offline motorollin

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #76 on: June 04, 2006, 11:21:52 AM »
The files you are opening, are the opening on to an RTG screenmode, or a native Amiga screenmode?

If they are opening on an Amiga screenmode then the app may use chip RAM. Try FBlit, it may be able to move the graphic in to fast RAM. Alternatively, open the graphic on an RTG screenmode and it should use fast RAM.

--
moto
Code: [Select]
10  IT\'S THE FINAL COUNTDOWN
20  FOR C = 1 TO 2
30     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NAAAA
40     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NA-NA-NAAAAA
50  NEXT C
60  NA-NA-NAAAA
70  NA-NA NA-NA-NA-NA-NAAAA NAAA-NAAAAAAAAAAA
80  GOTO 10
 

Offline whiteb

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #77 on: June 04, 2006, 11:37:42 AM »
A500 WAS able to handle 2MB chip.  You needed....

1) 2MB Agnus
2) Perform motherboard trace modifications

One day I'll get out the instructions for my 4MB trapdoor expansion.
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Offline whiteb

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #78 on: June 04, 2006, 11:43:03 AM »
Quote

@leirbag
Please, please prove us all wrong by re-designing the custom chips, rewriting kickstart and extensively modifying an A4000 motherboard. When I see the board, and watch the machine boot with no startup sequence and report 8MB of chip RAM, then I will believe it is possible :roll:
moto


I cannot see that is ISNT possible, talking about Minimig, if someone was to give Dennis the specifications so he can apply them to the Agnus section of the Minimig core.

Problem being, is then you need 8MB of ram on the minimig board for Chipmem, PLUS fastram.. and I believe that Dennis (last I heard) is running low on transistors on the core for the package he is using to store the chipset on.
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Offline motorollin

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #79 on: June 04, 2006, 02:13:39 PM »
Quote
whiteb wrote:
if someone was to give Dennis the specifications so he can apply them to the Agnus section of the Minimig core.

They don't exist...

--
moto
Code: [Select]
10  IT\'S THE FINAL COUNTDOWN
20  FOR C = 1 TO 2
30     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NAAAA
40     DA-NA-NAAAA-NAAAA DA-NA-NA-NA-NA-NA-NAAAAA
50  NEXT C
60  NA-NA-NAAAA
70  NA-NA NA-NA-NA-NA-NAAAA NAAA-NAAAAAAAAAAA
80  GOTO 10
 

Offline Doobrey

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #80 on: June 04, 2006, 02:44:59 PM »
Quote

whiteb wrote:

I cannot see that is ISNT possible, talking about Minimig, if someone was to give Dennis the specifications so he can apply them to the Agnus section of the Minimig core.


IMHO,the big problem will be compatibility with existing hardware.
The way UAE adds 8Mb of chip mem is to simply add another 6Mb at $200000(plus associated address decoding).
 But this memory range is already reserved for other things like the PCMCIA slot on the A1200/600 and ZorroII memory boards, and there's really no other place it can be added inside the 24bit address range.
 And you're stuck with a max of 2Mb fast mem if you're using a 68000 or 68ec020..plus you'd have to hack expansion.library to stop it configuring any boards into the 'new' chip mem area.
On schedule, and suing
 

Offline xeron

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #81 on: June 04, 2006, 04:30:34 PM »
Any suggestions of using MiniMig to create a replacement chipset for an existing Amiga motherboard won't come to anything, either. The schematics are not available for the chipset, and the MiniMig doesn't aim to emulate the chipset at a hardware level. It really only emulates the chipset at a register level so AmigaOS can run on it.
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Offline hazydave

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Some True Stuff from Dave
« Reply #82 on: June 04, 2006, 05:16:27 PM »
Hey all-

I think most of you are on-target here for the question, but I'll summerize.

The basic issue around existing chips is ONLY Agnus/Alice. There are internal and external limits to memory addressing on any device.

For the external world, on the chip bus, there are actually two: the limits on the system address bus to Agnus/Alice (how much of the CPU bus can the chips see) and the limits to addressing of the memory chips themselves on the multiplexed DRAM bus. Internally, there's the secondard issue of how much memory Agnus/Alice can directly access in DMA.

The reason upgrades were possible at some point in time was simply that these two didn't match. It was fairly easy, for instance, when going from thin Agnus to Fat Agnus, to allow a larger CPU and memory address bus.. that was all new logic, and kind of on the periphery of the chips (in the thin Agnus circuitry, much of this stuff was done in the system, not the chip anyway).

So an Agnus chip might allow CPU access to 1MB of memory, but only 512K of that could actually be chip memory, since the internal addressing counters in Agnus only supported 512K of address space. Once you had a similar design with more bits for actually memory addressing directly by Agnus/Alice, all of that addressed memory could be chip RAM. If you added more address bits still, that wouldn't help, since then the external interfaces would be limited in address space (much like the 68000 was logically 32-bit inside, but only brought out 24-bits worth of address space).

It's only Agnus/Alice in question, due to the way the chip work together. Agnus is generating all of the chip RAM addresses, regardless of what's happening on the chip bus. Sometimes, it's a memory cycle from the main CPU, sometimes it's a display fetch or audio cycle, sometimes a blit cycle, etc. In conjunction with the memory address bus there's the register access bus (RGA bus), which is seen by Paula and Denise/Lisa.

The specific register access code tells the whole chip bus what kind of access this is. Sometimes, it's Agnus or the CPU writing to a register physically located in another chip, which means there's no DRAM cycle at all. On a video fetch, for example, the memory access will be put out from Agnus's video counters, and the RGA code tells Denise to read the DRAM bus and shift that value into one of the bitplane shift registers. Same idea with Paula accesses... all of the memory access/counting stuff takes place in Agnus or Alice. So that's the one chip that would need to change if you wanted more chip memory.

Even AAA worked much the same, with the Andrea chip doing the Alice/Agnus piece. There was some additional complexity, like dealing with the line buffer chips (Linda), the ability to handle VRAM or dual Linde/Monica pairs to support a 64-bit graphics bus (the graphics data bus wasn't always the same as the main chip databus), but the basic idea was similar.

In an emulator, of course, you can try to perfectly emulate an existing Amiga chip, but there's no reason you can also emulate chips that never existed. If it's a simple thing, like more Chip RAM, the OS already supports it, maybe with a little help (eg, it may not detect 8MB automatically, but it knows what to do with it when it's there).

The 8MB/2MB jumper in the A4000 was put in there based on the identical jumper in the A3000+. When we were working out the last details of the AA chipset (we == me, Bob Raible, Victor Andrade, and George Robbins), Bob was building Lisa in CMOS, Victor was doing Alice in NMOS. The NMOS design limited the changes that could be made ... Agnus was already close to the limits of that technology. We hoped to be able to do a followup AA+ with a CMOS Alice, and if so, that was going to handle at least 8MB of Chip RAM. So we stuck the means for that into the early design, and we (meaning mostly Greg Berlin and Scott Schaeffer, with a little of my help) carried it forward into the A4000. But there was never a chip built that could use it.

If someone built an add-on that could perfectly replicate the function of the custom chips, there no reason they couldn't support 8MB of Chip RAM, of course. However, this is inherently a hack, because the only place you can all the signals needed to replace the three chips is at the chip bus itself. You'd have to physically replace the custom chips, you couldn't do this on a Zorro card, at least not without big software changes (interrupts you can't generate on the expansion bus, things like that).

-Dave
 

Offline Matt_H

Re: Some True Stuff from Dave
« Reply #83 on: June 04, 2006, 05:30:00 PM »
@ hazydave

Thanks, Dave!

@ all

The master has spoken. End of discussion :-D
 

Offline Zac67

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Re: Some True Stuff from Dave
« Reply #84 on: June 04, 2006, 05:40:49 PM »
 :bow:

One thing confuses me though: in the A4k, Alice has the complete address bus connected, so in theory you would 'only' need to
- redesign Alice for larger registers
- the 11 DRAM bus lines should be enough for 8 MB
- put in an 8 MB PS/2
and off you go (apart from OS/Zorro issues).
 

Offline redrumloa

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Re: Some True Stuff from Dave
« Reply #85 on: June 04, 2006, 06:21:28 PM »
Nice to see your input here Dave, thanks :-)
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Offline Tricky

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #86 on: June 04, 2006, 06:23:41 PM »
Quote

Piru wrote:
Not quite. For example the blitter queue of the OS itself is run from interrupts. Forbid() + WaitBlit() doesn't guarantee that further blits won't happen.


So you are saying there is no way to wait until the blitter finishes?  I find that rather hard to believe.  Surely a lot of games rely on the OS not suddenly using the while its running.  At least nothing more will be added to the queue whilst you are in forbid mode.

Quote

You misunderstood. Audio interrupt occurs when the sample playing has finished, where the interrupt code is located is irrelevant.

No I think you misunderstood me.  I know what the problem is with audio interrupts, and I wasn't disagreeing with you.  I was saying that there may be a lot of other interrupts that also may access chip ram and cause a problem.

Quote

Quote
I know it's common, but the official commodore line was always that you weren't supposed to use the hardware directly.

It was? Where did they say that? If so, why did they publish hardware reference manual with examples on how to use the hardware directly?

That's what I was always led to believe, at least for O/S friendly applications.  I guess they publish the hardware details for games writers.

Quote

Quote
Even still, as I already said, you'd need to be on the workbench screen to swap the app out anyway so this won't apply.

I wouldn't consider this very usable solution then.

I don't see why, as you have to be on the workbench screen anyway to run another program.
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Offline KThunder

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #87 on: June 04, 2006, 07:28:16 PM »
hey dave,
what do you think of the minimig project? most of us think its pretty cool but i dont think i saw your opinion on it anywhere.
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Offline Piru

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #88 on: June 04, 2006, 08:16:50 PM »
@Tricky
Quote
So you are saying there is no way to wait until the blitter finishes?

Sure there is, but your proposals are not working.

Quote
I don't see why, as you have to be on the workbench screen anyway to run another program.

You say it is possible to write such "swap" program. I still think it's not very stable solution, various things can easily break it. Lets agree to disagree, shall we?

I will hold my POV until you provide a working chipmem extender program. :-)
 

Offline Tricky

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Re: 8 Mb CHIP RAM on All Amigas
« Reply #89 on: June 04, 2006, 09:34:02 PM »
Quote

Piru wrote:
You say it is possible to write such "swap" program. I still think it's not very stable solution, various things can easily break it. Lets agree to disagree, shall we?


I don't even think we need to go as far as that.  You are exactly right, it wouldn't be fool proof, but it would be interesting to see if it could be done at all.  As I said, I'd have to write a lot of disclaimers in the readme!

Quote
I will hold my POV until you provide a working chipmem extender program. :-)

That's fair enough.  I have other things to write just now, but I'll write a memory tracker patch as a first step soon as I finish Mr Beanbag.
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