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Old 07 February 2019, 19:15   #1
Sim085
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Accelerator card in A500 bottom expansion slot?

I have always been under the impression that the bottom expansion port was there only to provide the A500+ with an extra 1MB of ChipRAM, and the case of the A500, with an extra 512KB of SlowRAM and Battery.

However today I came across this:
http://amiga.resource.cx/exp/powerpc

From what I can understand this takes control from the motherboard 68K processor to its own NEC V30 processor to emulate a PC on the amiga. This sounds similar to the accelerator boards of the A1200 where the processor on the accelerator board takes over control from the 020 on the motherboard.

So I was wondering; does the design of the A500 and A500+ allow for-example an 020 or 030 accelerator card to be installed in the bottom expansion port? If yes how come (to my knowledge) no 68K accelerator was designed in this fashion?

Last edited by Sim085; 07 February 2019 at 20:14.
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Old 07 February 2019, 22:32   #2
ovale
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The website is wrong. It adds chip/slow RAM not fast RAM. Indeed, all the ads don't say it is fast RAM.

I think it works by having both the 68k and x86 running in parallel.

The RAM is shared and used to exchange data and commands. On the Amiga side runs software that serves request from the x86 side interfacing with the keyboard, serial, HDD, etc. The Amiga emulates the EGA/CGA and sound cards too.

The RAM disk is because the original a500 (Agnus really) cannot address more than 0.5mb of slow RAM.

The Amiga fast RAM can be seen by the x86 because EMS is a bank switching system. I imagine the driver just copies the data back and forward when the BIOS wants to switch bank.
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Old 07 February 2019, 23:08   #3
Niklas
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Quote:
Originally Posted by Sim085 View Post
So I was wondering; does the design of the A500 and A500+ allow for-example an 020 or 030 accelerator card to be installed in the bottom expansion port? If yes how come (to my knowledge) no 68K accelerator was designed in this fashion?
The trapdoor expansion does not allow for a 68k accelerator; it's a DRAM bus only. However, as pointed out by ovale, the memory on that bus can be shared with another processor which can then be used as a co-processor. The project mentioned here also does this: http://eab.abime.net/showpost.php?p=...8&postcount=13

If you're interested you can have a look at the schematics, https://www.amigawiki.org/dnl/schematics/A500_R6.pdf, page 4 (sheet 3), to see what signals are connected to the trapdoor expansion slot.
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Old 08 February 2019, 15:37   #4
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That really looks like a great project. Does this project (A314?) have its own page? I have gone through the linked thread.

How is this planned to be used? the onboard processor offloads instructions to the co-procesor (in this case the raspberry pi) through the shared memory and then collect the execution results?

Or a way to share the raspberry pi resources (ex: network interface) with the amiga?

Quote:
Originally Posted by Niklas View Post
The trapdoor expansion does not allow for a 68k accelerator; it's a DRAM bus only. However, as pointed out by ovale, the memory on that bus can be shared with another processor which can then be used as a co-processor. The project mentioned here also does this: http://eab.abime.net/showpost.php?p=...8&postcount=13

If you're interested you can have a look at the schematics, https://www.amigawiki.org/dnl/schematics/A500_R6.pdf, page 4 (sheet 3), to see what signals are connected to the trapdoor expansion slot.
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Old 10 February 2019, 17:02   #5
Niklas
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Does this project (A314?) have its own page?
I'm afraid there's no web page for it yet; it's on the to do-list.

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How is this planned to be used? the onboard processor offloads instructions to the co-procesor (in this case the raspberry pi) through the shared memory and then collect the execution results?
Here's a short description of how it works. There are drivers running on both sides; DEVS:a314.device on the Amiga side and a314d on the Raspberry side. A program on either side (but typically the Raspberry side) can register a service. A program on the other side can connect to that service, and a logical channel is established between them. Messages (packets) are sent through those logical channels. Each service is free to define how packets sent to and from it are interpreted. The A314 implements interrupts to notify either side that there are packet(s) available for reading in a logical channel.

For example, the file system a314fs works as follows: a program on the Raspberry (a314fsd) registers a service with a certain name ("a314fs"). The file system is implemented on the Amiga side as a file system handler (L:a314fs) which immediately connects to the "a314fs" service and thus establishes a logical channel. After that, the Amiga side forwards each file system operation (list files, read file, etc) to the Raspberry through that logical channel, the Raspberry performs the file operation on its local file system, and then sends a packet back with the result of the operation.

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Or a way to share the raspberry pi resources (ex: network interface) with the amiga?
Exposing the Raspberry's network interface on the Amiga is certainly possible (see http://eab.abime.net/showthread.php?...52#post1294452).
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Old 18 April 2019, 12:43   #6
Eriond
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Sneak preview

A few boards have been made in their latest iteration, beta-2. They work perfectly, hours on end. We have identified one (!) issue where the board wasn't working properly, and that was the combination R5 motherboard - 8371 Agnus - HC508 turbo @ 50 MHz. Change any of those parametrs, and it works just fine
And here's the hardware p0rn you've been waiting for:
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Old 18 April 2019, 13:23   #7
indigolemon
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Excellent work
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Old 18 April 2019, 13:31   #8
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Can't wait to get one!
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Old 18 April 2019, 14:22   #9
PR77
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I'm really excited to see more on the A314. Keep up the great work.
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Old 19 April 2019, 18:45   #10
Mark sealey
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Awesome project....I want one too lol
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