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Thread: A2091ToFast: Even more A2091/A590 speedup possible!

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    Lightbulb A2091ToFast: Even more A2091/A590 speedup possible!

    A2091ToFast V2.5
    Original code by Chris Weber 1998 (Aminet). Updated and enhanced by SpeedGeek 2015.

    INTRODUCTION:
    A2091ToFast copies the A2091/A590 ROM code into Fast memory similar to the CPU FastROM command but does not require an MMU. This allows it to work with many other CPUs which don't have an MMU or free the MMU to perform other tasks. More importantly, it can speed up the execution of the SCSI driver code by SEVERAL HUNDRED percent!

    Note: Zorro2 Fast memory and Zorro2 ROMs operate at the same bus speed so there is no benefit to using A2091ToFast on a "Bog Standard" 7 MHz 68000. However, unlike the Zorro2 ROMs the Zorro2 Fast memory can be cached so the L2 cache on some 68000 accelerators (or the L1 cache on 68020+ accelerators) may still realize some benefit.

    I've uploaded RSCP images showing PIO speed on my system is now a little faster than original DMA speed (and much faster than ROM based PIO speed). Enjoy!

    P.S. If I were AndyLandy I would not be surprised it's possible to squeeze a few more drops of performance from our trusty old C= SCSI controllers!

    P.P.S. Another thread will posted on EAB to satisfy non-Amibay member download issues.
    Attached Thumbnails Attached Thumbnails A2091TOFAST_PIO.PNG   A2091ROM_PIO.PNG  
    Attached Files Attached Files
    Last edited by SpeedGeek; 24th July 2015 at 15:00.

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    decrunching Amibayer! Paul_s's Avatar
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    Excellent mod.... you should change your name to Dave Haynie

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    Cheers SpeedGeek. Ima try it and report back
    Visit my Amiga Blog: http://www.mfilos.com
    - A600: Vampire V2, 128MB, A604n, 16GB CF, Indivision ECS, RapidRoad USB, Ratte's auto RTG/ECS switch, Gotek w/HxC-LCD + Slim floppy (internal)

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    Haven't checked what the code actually does, but the os does not execute driver code on zorro2 cards from their rom.

    The content is copied into system memory at boot and ends up in whatever fully autoconfig memory that has the highest priority, which should be your fastest ram unless you have a quirky mem-expansion. Just check under devices in say sysinfo to see what's the case.

    If you have a quirky expansion the driver could end up I'm chipmem though.

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    Quote Originally Posted by SpeedGeek View Post
    P.S. If I were AndyLandy I would not be surprised it's possible to squeeze a few more drops of performance from our trusty old C= SCSI controllers!
    With guys like you around, the sky really is the limit! It wouldn't surprise me if one of these days you'll have an Amiga running a 500MHz 68k CPU core and a custom Zorro bus that runs at 1:1 with it!

    Awesome stuff on the mods there. It never ceases to amaze me what folks (you in particular) seem to be capable of making our old hardware do!

    Thinking about accelerating your A1200? Check out my buyer's guide.

    Projects past and present: Amiga 2000/030 | Amiga 3000/040 | Amiga 4000/060

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    @Paul_s
    I might be able to pull that off in U.K. but here in U.S.A. I could easily get sued for defamation of character, slander, theft of intellectual property, etc.!

    @mfilos
    I didn't even know you had an A2091/A590 my friend! But I'm happy to see your full report: mfilos = Beta tester par excellence!

    @Patrikax
    Sorry, most expansion ROM drivers don't get copied into any memory (the Guru ROM being a notable exception here). What does get copied in memory is the ConfigDev info for the device and a jump table for any libraries or task structures used by that particular driver.

    @Thread
    Here is some interesting info from the Amiga RKRM:
    "The A2091, A590 and A3000 drivers always do programmed I/O for data transfers under 256 bytes or when the DMA chip doesn't support the required alignment."
    Last edited by SpeedGeek; 2nd July 2013 at 20:35.

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    Are you sure about them not being copied to system ram in the general case?

    It's very long time since I messed with that stuff, but I remember that there were provision even for supplying the driver rom as 4-bit wide rom (indicated somehow via autoconfig) and the 68000 could not run code directly from such a rom.

    So got the impression that in the general case stuff was copied. Of course you should be able to do solution where you point to the rom instead in a small init code (if it is presented as 16-bit on the bus), letting the CPU execute directly from it and save a little bit of memory.
    Last edited by Patrikax; 1st July 2013 at 09:45.

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    Thank you

    I'll give it a try next weekend.

    :rainbow:Amiga + C64 :rainbow:

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    Quote Originally Posted by Patrikax View Post
    Are you sure about them not being copied to system ram in the general case?
    Yes, I'm quite sure. In post #1 I've uploaded an RSCP image for ROM based PIO on the same system. It takes several minutes to run the test and the results speak for themselves!

    Also, it appears as though you have confused Auto-Config ROM with expansion driver ROM.

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    Not saying that the A2091 doesn't run the code directly from the rom - it is after all a card with double eproms (odd/even) design which would be a quite unecessary if the rom data is just copied to ram.

    However, the general case - zorro2 cards usually only have one 8-bit rom with very slow access time (200ns). Even with the logic to deliver it 16-bit at a time to the cpu to allow execution to even take place, it would result in slow execution times of the driver code even on a plain 68000 and should be a well known performance problem of cards with cpu-intensive code, say PIO-only cards.

    I found the rkrm libraries part I remembered about the copying (DiagArea):
    http://gega.homelinux.net/AmigaDevDo....html#32-3-3-1

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