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Virtual Motorola 68000 "m68k" Machine With Up To 3.2GB RAM Expected For Linux 5.19

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  • ayumu
    replied
    Originally posted by Chewi View Post

    Great explanation! I still fondly remember this icon.

    That is a workaround for very early, buggy applications.

    The very first Amiga only shipped chip ram, and some early applications failed to request chip ram for memory that actually needs to be visible by the chipset, such as graphics data to be set up as display. Forcing all allocations to be on chipram would help these few, poorly programmed early applications work on any Amiga configuration.

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  • hotaru
    replied
    meanwhile, in an m68k chroot with qemu user mode emulation:

    Screenshot 2022-04-19 19.28.32.png

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  • F.Ultra
    replied
    Originally posted by stesmi View Post

    That's a way to put it!

    The Amiga chipset shared memory bus with the CPU, and the chipset could address 512KiB/1MiB/2MiB (8361/8367 Thin-, 8370/8371 Fat Agnus could do 512KiB, 8372A could do 1MiB, 8372B could do 2MiB, some 8375 could do 1MiB, some 2MiB, and everything later could do 2MiB). This RAM is then called "Chip RAM". The memory is slow, due to several factors.
    The shared memory bus could also take more RAM than that, but the chipset couldn't use it. The speed was still as slow as Chip RAM. This is generally referred to as "Slow RAM".
    Then there's other memory ranges that don't touch the chipset at all, and that memory is way faster, and therefor called "Fast RAM".

    What you have, with your 128MiB upgrade, is Fast RAM, but you still have 2MiB of Chip RAM, so that's why 128+2 = 130MiB.

    // Stefan
    Exactly, which is why even the Vampire have only 2MB of ChipRAM unless you use the SAGA where it goes up to 12MB but now we are no longer talking original hw.

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  • F.Ultra
    replied
    Originally posted by stesmi View Post

    Yup! I mean, you could theoretically stick 1GiB I believe into an Amiga A3000/A4000 using existing memory upgrade boards, but looking at the memory map I don't see a reason why that couldn't be roughly 2GiB. EDIT: 0x08000000 - 0x10000000 is available for Z3. 1920MiB.

    And with existing boards, I mean either a BigRAM Plus (256MiB per board) or ZorRAM (128/256MiB per board). Use 4 of those and voilá, 1GiB of RAM.

    Using a big enough hammer, I guess one could use 0x80000000 - 0xFF000000 as well, adding almost 2GiB more, but there could be limitations I'm not aware of. Z3 wouldn't autoconfigure it, I'm sure, but that wouldn't stop something else doing the deed.



    For sure, the I really liked the architecture. The 68008, I believe, was developed sort of at the same time, slightly after the 68000. I believe it was added due to some company (I can't remember who anymore) asked for it, so they wouldn't need to use a 16bit bus.

    // Stefan
    The total hardware memory space defined by the Amiga Zorro III expansion bus specification is actually only 1792 MB so that is the hard hw limit.

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  • Chewi
    replied
    Originally posted by stesmi View Post

    That's a way to put it!

    The Amiga chipset shared memory bus with the CPU, and the chipset could address 512KiB/1MiB/2MiB (8361/8367 Thin-, 8370/8371 Fat Agnus could do 512KiB, 8372A could do 1MiB, 8372B could do 2MiB, some 8375 could do 1MiB, some 2MiB, and everything later could do 2MiB). This RAM is then called "Chip RAM". The memory is slow, due to several factors.
    The shared memory bus could also take more RAM than that, but the chipset couldn't use it. The speed was still as slow as Chip RAM. This is generally referred to as "Slow RAM".
    Then there's other memory ranges that don't touch the chipset at all, and that memory is way faster, and therefor called "Fast RAM".

    What you have, with your 128MiB upgrade, is Fast RAM, but you still have 2MiB of Chip RAM, so that's why 128+2 = 130MiB.

    // Stefan
    Great explanation! I still fondly remember this icon.

    Leave a comment:


  • StarterX4
    replied
    16GB RAM in 2030

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  • stesmi
    replied
    Originally posted by Chewi View Post

    I suppose so, but I'm not sure that you can treat them equally. I was only a kid when I had my Amiga, so I never really took the time to understand the difference. Now I have so much that it doesn't matter!
    That's a way to put it!

    The Amiga chipset shared memory bus with the CPU, and the chipset could address 512KiB/1MiB/2MiB (8361/8367 Thin-, 8370/8371 Fat Agnus could do 512KiB, 8372A could do 1MiB, 8372B could do 2MiB, some 8375 could do 1MiB, some 2MiB, and everything later could do 2MiB). This RAM is then called "Chip RAM". The memory is slow, due to several factors.
    The shared memory bus could also take more RAM than that, but the chipset couldn't use it. The speed was still as slow as Chip RAM. This is generally referred to as "Slow RAM".
    Then there's other memory ranges that don't touch the chipset at all, and that memory is way faster, and therefor called "Fast RAM".

    What you have, with your 128MiB upgrade, is Fast RAM, but you still have 2MiB of Chip RAM, so that's why 128+2 = 130MiB.

    // Stefan

    Leave a comment:


  • Chewi
    replied
    Originally posted by ayumu View Post

    You sure you don't have 130? (128mb 32bit fastram + 2mb chip)
    I suppose so, but I'm not sure that you can treat them equally. I was only a kid when I had my Amiga, so I never really took the time to understand the difference. Now I have so much that it doesn't matter!

    Leave a comment:


  • stesmi
    replied
    Originally posted by SteamPunker View Post

    I was thinking the same thing. And the fact that Michael originally hails from Germany, where the Amiga was particularly popular, makes this omission even more awkward.

    Anyway, the fact that the m68k architecture continues to thrive in virtual form to this day, supporting almost 4GB of RAM(!!!)
    Yup! I mean, you could theoretically stick 1GiB I believe into an Amiga A3000/A4000 using existing memory upgrade boards, but looking at the memory map I don't see a reason why that couldn't be roughly 2GiB. EDIT: 0x08000000 - 0x10000000 is available for Z3. 1920MiB.

    And with existing boards, I mean either a BigRAM Plus (256MiB per board) or ZorRAM (128/256MiB per board). Use 4 of those and voilá, 1GiB of RAM.

    Using a big enough hammer, I guess one could use 0x80000000 - 0xFF000000 as well, adding almost 2GiB more, but there could be limitations I'm not aware of. Z3 wouldn't autoconfigure it, I'm sure, but that wouldn't stop something else doing the deed.

    Originally posted by SteamPunker View Post
    and having first class support in Linux, really speaks for the amazing forward compatibility that the 68000 was endowed with when it was initially designed and developed. If only IBM had gone with the 68000 CPU in the original IBM PC design, instead of the 8088, the PC platform would have been so much nicer, with much smoother generational upgrades.

    Maybe if Motorola had released the low cost 68008 variant a few years earlier. Alas.
    For sure, the I really liked the architecture. The 68008, I believe, was developed sort of at the same time, slightly after the 68000. I believe it was added due to some company (I can't remember who anymore) asked for it, so they wouldn't need to use a 16bit bus.

    // Stefan
    Last edited by stesmi; 19 April 2022, 02:37 PM.

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  • Waethorn
    replied
    Didn't they remove the floppy drive code already?

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