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The default speed of the Mega65

  • To what Speed should the Mega65 default on startup? 37

    1. 3.5MHz (13) 35%
    2. 40MHz (24) 65%

    There's a discussion going on currently in the discord about whether the ROM should default to 3.5 or 40MHz. It looks like the 40MHz option won, but I only read discord because I don't have an account, so I still made this poll. :P


    There's those who say that 3.5MHz would be more true to the original C65, and those who say that nobody wants to use 3.5MHz anyway.


    I have to say I can understand those who argue for 3.5. The whole point of the Mega65 is to recreate a wacky computer from the 80s, and then improve it. Making it the other way around makes it feel like it's a modern retrocomputer that can also mimic a C65.

    The same argument that goes against 3.5 MHz also applies to the floppy drive, the memory layout, bitplane modes, etc. When you recreate all those things but then decide to make it run on 40MHz by default, it feels like the computer got schizophrenia in the last minute.


    Also, there's a reason old PCs had a Turbo button, not a slowdown button. It's way cooler to have a button that speeds up your computer than one that slows down your computer.

  • To me it always seemed a bit weird why it's 40 MHz. Since the C65 had 3.5 MHz, I could understand if it was 7 MHz or even 14 MHz, but 40 seems a bit arbitrary, especially the huge gap between 3.5 and 40.

  • Also, there's a reason old PCs had a Turbo button, not a slowdown button

    As is anybody ever switched off the turbo mode. Actually, it was a throttle button anyway and calling the default mode (with throttle disabled) "turbo" was just marketing.


    This being said: the C65 never went into production, I guess there aren't any games etc. that would rely on the 3.5MHz. If 40MHz is a supported frequency that complex games/tools can rely on, it must be either the default or switchable by register access. Now, if at some point most games will switch to 40MHz anyway and defaulting to 3.5MHz is not needed for compatibility with existing titles, what sense does it make to start with 3.5MHz?

    Or to phrase it differently: if the goal of implementing 40MHz wasn't to use it, why was it implemented in the first place?

    For comparison: the U64 can be sped up to 48MHz, but as the U64 is a C64 with almost all existing programs relying on the 1MHz timing, it wouldn't make sense to use anything else than ~1MHz as the default.
    This reason doesn't seem to exist on the Mega65. So why bother with throttling?

  • I like to start it slow, because

    A) most basic programs are written for the C64 currently, and timing issues wouldn‘t appear

    B) listing directories isn‘t fun in high speed, and wide listings will eliminate the direct loading comfort

    C) debugging is more valueable when going step by step, than all at once

    D) it‘s a nice showcase for newbiews to the retro machines showing them what once was and can be

    E) I don‘t drive at max. speed all the time, either

    F) it reminds me of working on the good olde C64, with TBS like enhanced Basic

    G) there is no further native speed improvement (due to FPGA‘s I/O limitation)

  • Short version: I prefer 40MHz because it’s a MEGA65 and not a C65.


    I really don’t understand why it should use the C65 mode as default. Just to run properly some tech demos, which were written to show the capabilities of the C65? In my opinion the MEGA65 is a more advanced computer with the genes of a C65. Therefore it should use the 40MHz as default speed.


    When the MEGA65 should behave like a C65 for the good old times then it can switch the frequency down to 3.5MHz.

  • 99% of all BASIC 65 programs available so far have in one of the first lines a command to switch the MEGA65 into the 40 MHz mode. ;)


    The BASIC 65 was optimized by Bit Shifter in months of work laboriously also on runtime and accelerated significantly. The MEGA65 extensions, all of which were not present in the C65, were included in the BASIC 65 and are now easily usable.


    To Bit Shifter 's chagrin, I am one of the "C65 advocates" and have always pointed out to him "the compatibility" with the C65 BASIC. :D


    But, the MEGA65 is not a C65.


    With an original C65 ROM from Commodore, you have at least what comes closest to the C65: BASIC 10 and 3.5 MHz at startup. Also further, if one selects e.g. the 911001 or 911210 ROM.


    But with a new MEGA65 ROM with BASIC 65 it would be downright "stupid" to start the MEGA65 with 3.5 MHz. Why to provide the BASIC 65 after all these optimizations artificially 10x slower than possible? The C65 also starts in his highest available speed 3.5 MHz and not with 1 MHz because "of the C64 inside". ;)

  • Well, if the default mode would be 40 MHz, then why should anyone EVER switch into 3.5 MHz mode?


    Whereas if the default mode was 3.5 MHz, some people would just accept it, even for their BASIC programs, and only if they needed more punch, they'd speed it up. In a way, we're all looking for "restrictions" in the retro community, and 40 MHz feels very far apart already from the usual restrictions we have in our Commodore world.


    If 3.5 MHz is the default, people who love restrictions feel as if they have a baseline for comparison, and only those who either don't care or who just want to use it as a fast BASIC machine, would switch to 40 MHz. But if someone creates a demo which runs in standard mode (3.5 MHz), be it either in assembly or BASIC, would still earn his respect. If 40 MHz was the default instead, things would feel differently. "Oh you made a demo for the 'slow' mode? Ok nice... but why?"


    Also, for me the MEGA65 is still a "vastly finished C65", it is often propagated this way ("finish what Commodore didn't finish"). Yes, it has more features, but actually I always found the 40 MHz mode a strange choice, even if it sure is a nice way out of BASIC slowness. 40 MHz is even a lot more than the typical Amiga has! It's really more of a "turbo" mode in my opinion, than a standard mode.


    In my opinion, "standard" mode (3.5 MHz) and "turbo" mode (40 MHz) makes much more sense than "standard" mode (40 MHz) and "super slow" mode (3.5 MHz).

  • Imo it should be started by default with 40 MHz. It's the Mega65, a new 8bit fpga machine which also offers compatibility to (and looks like) the c65 pre series models.

    And the people who want the c65 mode can use it, like with the c128 where 95% of users used only c65 mode.


    And why not a setting like "start mode: c65/m65"?

  • Well, if the default mode would be 40 MHz, then why should anyone EVER switch into 3.5 MHz mode?

    If no one want use the 3.5 Mhz why should it be the standard?

    Well as I explained, I think people might use the 3.5 MHz mode more if it was at least considered the "standard baseline", and 40 as a turbo mode (40 MHz is even considered turbo in the Amiga world). But if 40 MHz is standard and 3.5 MHz is "slow mode", I think no one is ever going to switch into it, which makes me wonder why it's even available at all (yes, maybe for running that one C65 demo, but apart from that?)

  • Well as I explained, I think people might use the 3.5 MHz mode more if it was at least considered the "standard baseline", and 40 as a turbo mode (40 MHz is even considered turbo in the Amiga world). But if 40 MHz is standard and 3.5 MHz is "slow mode", I think no one is ever going to switch into it, which makes me wonder why it's even available at all (yes, maybe for running that one C65 demo, but apart from that?)

    With SPEED 1 you can even switch to 1 MHz. :D


    Sorry, but I find it more than stupid to optimize a BASIC for months, among other things also for speed, and then not let the computer start at its maximum speed, but more than ten times slower than possible.


    The MEGA65 is a computer that runs at 40 MHz.


    And that is just the way it is. As I said, almost every BASIC65 programmer switches to the 40 Mhz anyway, because it just works.


    The C65 is also started in its maximum speed (3.5 MHz) and not with 1 MHz (because there is still a C64 mode).

  • Well you simply repeated your arguments, and now I could repeat mine once more, but this is not a discussion ;)


    To me, the 40 MHz always seemed like a bonus thing. A nice extra that you can use if you want or need it, added on top to the C65 heritage. When things are turned around, and "turbo" mode becomes default, then there is absolutely next to zero reason for the slow mode to even exist. Of course it would be even more mad to get rid of it, since that would break C65 compatibility once and for all. But still, if turbo becomes default, the former default becomes "slow mode", and thus a "feature" that will probably never get used at all.