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Old 27 September 2019, 18:34   #1
Sim085
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Bought a 68010

Bought a 68010P12 from China. Might never arrive but who knows. Anyway, going to the real question, read many people say that a 68010 is not worth it because some software does not work on it. I found this (Fix68010.lha) on aminet. Is this enough for a stable system? Or I need further patches?

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Old 27 September 2019, 18:43   #2
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You probably don't even need that with modern software. Whatever modern means. Anything done after 1990 probably.
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Old 27 September 2019, 20:39   #3
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The 68010 improves a couple of things:
  • Small instruction cache for really small loops
  • Allows moving the VBR to fast ram.
Expect a 10% speedup. I think there are some WHDLoad improvements.
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Old 27 September 2019, 22:29   #4
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the only visible improvement under whdload is that it uses VBR moving to install quitkeys if slave doesn't have 68000 quitkey support.

Also if the game catches an illegal instruction or such, whdload can trap that, instead of crash/custom game exception handling that is just useless as it displays a red screen & loops or whatever.

Of course if the slave has been reworked to add a 68000 quitkey and doesn't crash, it's not that useful It could be useful if you use your machine to develop whdload slaves. But in 2019 that would be very hardcore when we have winuae & cross development tools like vasm.
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Old 01 October 2019, 22:10   #5
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I'd say expect a 5% speedup, 10% is very, very optimistic. The virtualization features are pretty much the only win in the 68010, which does help with WHDload but does mean that a lot of very old stuff will now *have* to be run with whdload patches instead of running the original releases.
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Old 01 October 2019, 23:34   #6
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I was thinking, given this is a P12 can I change the crystal on the A500 to a 12Mhz? or that the other stuff on the board don't work at that speed?
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Old 02 October 2019, 00:20   #7
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No, the 28 MHz cystal also steps all other chips. Even if they would take the higher frequency, video would be out of sync. You can try to just clock your CPU at 14MHz, half of the main clock instead of a quarter. But you'll have to look up the details. There will be a howto on aminet if it's doable.
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Old 02 October 2019, 11:10   #8
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Quote:
Originally Posted by Sim085 View Post
I was thinking, given this is a P12 can I change the crystal on the A500 to a 12Mhz? or that the other stuff on the board don't work at that speed?
Find a schematic for a 14MHz solution that divides down from the main 28.xyz clock, and takes care of E-clock, etc.
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Old 02 October 2019, 17:32   #9
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that is intresting ... but wouldn't 14MHz fry a 12MHz CPU? Or it is within the limits of this?

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Find a schematic for a 14MHz solution that divides down from the main 28.xyz clock, and takes care of E-clock, etc.
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No, the 28 MHz cystal also steps all other chips. Even if they would take the higher frequency, video would be out of sync. You can try to just clock your CPU at 14MHz, half of the main clock instead of a quarter. But you'll have to look up the details. There will be a howto on aminet if it's doable.
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Old 02 October 2019, 18:03   #10
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It would probably be fine, it's not a huge overclock and the 68000 only gets a little warm. But the bigger issue is that, even with the CPU running at double the speed, most operations won't get any faster because the bus is still running at the original speed. You really need some local fast RAM than can use the CPU's extra speed to make it worthwhile.
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Old 03 October 2019, 12:51   #11
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If the CPU is on its own board does that mean the A500 motherboard would keep its original crystal while the new board would have its own crystal?



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It would probably be fine, it's not a huge overclock and the 68000 only gets a little warm. But the bigger issue is that, even with the CPU running at double the speed, most operations won't get any faster because the bus is still running at the original speed. You really need some local fast RAM than can use the CPU's extra speed to make it worthwhile.
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Old 03 October 2019, 13:27   #12
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Well, that might work in theory with a bit of extra circuitry, but that's not how the hack normally works. The best way of doing it would be to derive a 14MHz clock from the motherboard clocks so that the CPU remains in sync with the rest of the machine, and it all still runs off the motherboard's crystal as before. Some of the other signals e.g. the peripheral clock will run at an incorrect speed too, which could cause problems but can easily be rectified with a small bit of logic.
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Old 03 October 2019, 15:29   #13
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This sounds similar to the overclocking mod carried out on the megadrive but in that all most do is lift pin 15 of the chip and route your own higher clock to that from a seperate crystal. Its very hit and miss thought. I tried it myself and it works but the machine is only stable for seconds before everything gets out of sync and you get graphics corruption.

It may work on the A500 with a double clock so 14mhz but I find it very unlikely it'll be stable or it'll actually be of any use. I mean if it was than why doesn't everyone have this mod done or why didn't commodore do it themselves.

It wouldn't be that hard to do though so might be worth a go if just to see what happens.
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Old 03 October 2019, 16:08   #14
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It should be stable if it's synchronised with the motherboard, the main problems are:

- the peripheral clock will also be double speed, messing up things like CIA timing that can affect some games (fixed using a toggle flip-flop to halve its frequency)

- it's mostly pointless because the CPU has to wait for the motherboard RAM to do anything anyway. The 68000 has no cache to use, and the 68010 cache is so small that only very specific code can take advantage of the speed. So your 68000 could be 1GHz, but it still has to access the chip RAM at 7MHz to load an instruction or data and store a result.
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Old 03 October 2019, 21:13   #15
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It should be stable if it's synchronised with the motherboard, the main problems are:

- the peripheral clock will also be double speed, messing up things like CIA timing that can affect some games (fixed using a toggle flip-flop to halve its frequency)
Many years ago (1993?) I was living in the Netherlands and I bought a 16Mhz 68000 board from a local fair. It had this problem. The system clock ran twice as fast!
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Old 03 October 2019, 23:19   #16
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Ok, please bare with me as I am no hardware wizard at all. I went to check and from what I can see the crystal on the A500 is 28.37156MHz (tbh I always thought it was 7.09MHz). So - based on this thread - I understand that the 7.09Mhz is derived from the 28.37156MHz clock (division 4).

So are we saying that if, from this crystal we also derive a separate 14.18MHz for the CPU, and the CPU has some fastRAM available to it, then you would gain an advantage without any incompatibility?
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Old 04 October 2019, 11:03   #17
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Basically, yes, dividing the 28MHz signal by two will give you your 14MHz synchronous CPU clock. You can use the same idea then to divide the peripheral clock from the CPU by two as well, avoiding problems with CIAs etc.

If you're adding some fast RAM though, you'll need a RAM controller. You might as well also add the additional logic needed to make it asynchronous, and then run it at any speed that the CPU can by having a separate crystal. This is how most accelerators work.

The Amiga uses a ~28MHz crystal to control the video output, and all other clocks are derived from that so that everything on the motherboard runs in sync.
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Old 04 October 2019, 12:29   #18
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Out of interest has anyone tried to overclock the whole machine and use a different crystal to control video sync only?
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Old 06 October 2019, 11:03   #19
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Quote:
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Out of interest has anyone tried to overclock the whole machine and use a different crystal to control video sync only?
Can't do that, because the entire video generation, DMA fetch, audio frequencies, bus arbitration, etc. is ALL in lockstep with NTSC/PAL. At best you'd have some weird "time-warp" Amiga operating on a different plane of existence, and you could build a special video scan converter to bring the framerate back into reality (couldn't do anything about the audio though, really) and things would still be moving too fast.

In physical practice even this wouldn't really work as the Amiga custom chipset was never designed to clock at higher rates and would fail as you bumped up the overclocking, RAM chip latency would break fetches (RAM is built around analog latency limitations), etc.

Regarding just building a small PCB that runs the CPU at a multiple of the system bus frequency, this was actually a very common practice back in the day for inexpensive accelerator cards -- e.g. ICD AdSpeed, SupraTurbo, lots of no-name 68020 accelerators, etc. It dramatically simplifies bus arbitration letting you use very simple glue logic, with the added benefit of preserving maximum bus speeds. Some bits of software that were very sensitive to chipram bus latency don't work properly on many expensive asynchronous cards, but work fine on cheap synchronous ones because the bus signals always line up orthagonally.
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Old 07 October 2019, 20:44   #20
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Can't do that, because the entire video generation, DMA fetch, audio frequencies, bus arbitration, etc. is ALL in lockstep with NTSC/PAL. At best you'd have some weird "time-warp" Amiga operating on a different plane of existence, and you could build a special video scan converter to bring the framerate back into reality (couldn't do anything about the audio though, really) and things would still be moving too fast.

In physical practice even this wouldn't really work as the Amiga custom chipset was never designed to clock at higher rates and would fail as you bumped up the overclocking, RAM chip latency would break fetches (RAM is built around analog latency limitations), etc.
You can do that and it was made already on Amiga for Macintosh emulator to deal with variable speed FDD, almost each genlock do this on regular basis. If you re-clock Amiga then all timing will follow external clock - this has pros and cons (inability to read floppies after passing DPLL lock-in and track thresholds) another limitations will be related to DRAM cycle and of course overall IC's OC capabilities. I've made some experiments many years ago (by replacing main generator) and Amiga was easily accepting over 30MHz clock source.
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