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Old 22 March 2021, 17:09   #1
amiga_amigo
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Problem with configuring memory

Hello all,

i'd need some help from the Amiga gurus - so please halt your meditation for a second...
I recently got an A2630 for my aged Amiga2000 and now wanted to emulate my real system using WinUAE 4.4.
Since both of my internal floppies and my Syquest sq3270s external drive died, i hadn't touched this Amiga for years and getting it running again is a bit tedious.
I borrowed a floppy from my A500 for testing and that worked. Now, i'd like to try installing an sd-card "harddisk" using WinUAE and get a SCSI2SD for my A2000.
But step by step...
First about configuring WinUAE correctly. Two problems:

1) memory configuration:

My system:
Amiga (B)2000 (rev.6), 1MB chip
A2091, 1MB, rom v6.6
A2630, 4MB, rom v7

I started with an A500 quickstart config and modified it to use the A2000 chipset extra, CPU 68030, MMU, 68882 FPU enabled, 25MHz custom CPU frequency.
The "Chip" slider in "Ram" / "Memory Settings" is set to 1MB.
For the A2091 (configured with correct rom in "Expansions", DMAC-01), i used "Z2 Fast Ram #1" from the "Advanced Memory Settings" and set the slider to 1MB.
Manufacturer is set to 514 and Product to 2.
For the A2630 (configured with correct rom in "Expansions") i set the "Accelerator board memory" slider to 4MB.
Since these 4MB didn't show up anywhere, i used the "Z2 Fast Ram #2" from the "Advanced Memory Settings" and set the slider to 4MB as well. Manufacturer 514 and Product 81.

Now "Hardware info" shows this:
Code:
 -  A2620/A2630    0x00f00000 0x00010000 -
Z2  Z2 Fast RAM[2] 0x00200000 0x00400000 0x0202/0x51
Z2  A590/A2091     0x00e90000 0x00010000 0x0202/0x02
Z2  -Z2 Fast RAM   0x00600000 0x00100000 0x0202/0x51
First entry is the A2630 rom (?), second entry 4MB memory. Product id 0x51 == 81 ok.
According to the 2630 manual, memory is auto-configured first, so memory start at x200000 is fine i guess.
Third entry is the A2091 rom. Product id 02 ok.
But why is the 1MB ram assigned to id 0x51 instead of 0x02?

ShowConfig from Workbench also displays the 1MB as A2630 board instead of A2091.
Emulation works, but nevertheless i'd like to know what i'm doing wrong.
Surely the 4MB shouldn't be Z2 Ram, right? It's sitting in the processor slot...

So the questions are:
How do i configure the 1MB for the A2091 (or my whole system for that matter) correctly? Any tutorials i missed?
Also - how is the "Accelerator board memory" slider supposed to work? The 4MB are not appearing unless i use the "Z2 Fast Ram #2" slot.
But if i use this slot, i can set the "Accelerator board memory" slider to whatever i want - makes no difference (apparently).
Maybe someone can enlighten me?

2) 68000 fallback (maybe related to memory config?):

When booting with right mouse button pressed and selecting the 68000 fallback option, WinUAE reboots but stops immediately with a HALT2 condition.
Checking the GUI, i see the processor was set back to the 68000, MMU and FPU disabled, but emulation speed is still set to my custom 25MHz.
Pressing reset from the GUI restarts emulation with the 68030 again (which is fine).
Is the HALT2 due to my faulty memory configuration, a bug or is the fallback option simply not supported?

Thanks for your help,
Michael

Last edited by amiga_amigo; 22 March 2021 at 19:45.
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Old 23 March 2021, 18:00   #2
Toni Wilen
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Could you attach your config file?

I guess something goes wrong when there are multiple RAM boards and one of them is accelerator board, probably some combination that was missed.

It shouldn't affect how the board works so 68000 fallback probably is caused by something else.
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Old 23 March 2021, 18:33   #3
teppic
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On a real 2630 the 4MB is autoconfigured in the 8mb Z2 space, but it supports additional memory via a connected board and this isn't autoconfigured. I don't know if the ROM is supposed to deal with this or not.

I assume WinUAE is using the slider for this extra memory rather than the 4MB autoconfigured memory. It looks like you have to add the auto configured memory manually like you did.
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Old 24 March 2021, 09:10   #4
amiga_amigo
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Thanks for responding - here's the config.
Attached Files
File Type: uae My_A2000.uae (12.1 KB, 33 views)
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Old 25 March 2021, 19:01   #5
teppic
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Toni, I've a question on top of the OP's related to this - does WinUAE support the slow down that a 68030 like this would have when accessing the rest of the system? i.e. it runs at 25MHz when accessing its own RAM, but if it goes to chip RAM or the RAM on the hard drive it will drop to 7MHz, obviously causing a huge slowdown (on top of it being only 16bit).
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Old 25 March 2021, 19:51   #6
amiga_amigo
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I don't think the clock drops to 7MHz when accessing 16bit memory (chip or fast).
The manual mentions that appropriate waitstates are inserted to slow down the 68030 while accessing "A2000 resources" (so yes - it's similar to dropping the clock to 7MHz).
The 32bit memory on my 2630 is rated at 80ns whereas the 16bit ram on the 2091 is 70ns.
So i guess there are waitstates with onboard ram as well and the only difference in memory access is 16 vs 32 bits.
The 68030 has a (small) instruction and data cache to gain speed (don't know if the cpu/mmu does prefetch, though).

Last edited by amiga_amigo; 25 March 2021 at 20:02.
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Old 25 March 2021, 20:09   #7
teppic
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Yeah, it should use enough waitstates so that it is effectively 7MHz since it's not doing anything the rest of the time. If WinUAE doesn't emulate this though it'll be accessing the system at full 25MHz, making it a lot faster than the real hardware. (The latest beta has an option to set the extra RAM as 16bit, by default it'll incorrectly be accessed at 32bit)
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Old 25 March 2021, 20:40   #8
Toni Wilen
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Yes and no.

In cycle-exact mode ("memory cycle-exact" is enough) emulator does wait for free chip ram bus cycle but execution times aren't accurate.

68020+ internals are too unknown to be able to have cycle-accurate emulation ("unfortunately" 68020+ bus sequencer and instruction scheduler run separately).
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