4 ms·

Yep. The bummer is that the Apple ][ relies on the clock speed of the 6502 to handle some of its functionality (most notably video handling), so you can’t just

by dhosek 3y ago

Yep. The bummer is that the Apple ][ relies on the clock speed of the 6502 to handle some of its functionality (most notably video handling), so you can’t just run a cable to the CPU socket on the Apple motherboard. I wonder if any of the other classic 6502 machines (Commodore, Atari, Acorn, BBC, etc.) would work?

basementcat 3y ago
This is true of the Commodore 64 as the VIC-II chip timing is closely coupled to the NTSC color burst (note below joke about "up-scanning to 60 Hz") Also disk I/O and RS-232 are bit-banged.
- anyfoo 3y ago
  > Also disk I/O and RS-232 are bit-banged. You could easily slow that down as well. The big problem is really the CRT (and possibly other ICs in the computer that don't like the extreme slowdown). As noted below, if you went through the arduous process of replacing and retuning components to be able to slow the beam down, your phosphor coating is still too fast, and probably doesn't like having the beam passing only slowly over it. (You thought regular burn-in was bad!) However, replace the CRT with something else, like an LCD with some extra buffering circuit, and it could work. Yes, the color burst will be at a much lower frequency as well, but just demodulate color at this lower frequency, then.
  - dhosek 3y ago
    Yeah, I’m thinking that the solution would be something that takes the analog monitor signal and uses it to control a digital display.
tombert 3y ago
Again, I know basically nothing about hardware, so this is likely a dumb question: could you conceivably get an oscillator/clock chip that also operates at 1/20th the speed, wire that into the Apple ][, and then wire in this giant CPU?
- duskwuff 3y ago
  Unfortunately, no. The CPU would work, but memory retention would be unreliable (because the DRAM is now going ~20x too long between refreshes), and the composite video output would fail to display on a monitor (because it's the wrong frequency).
  - tombert 3y ago
    Well now I'm wondering; it might not directly run an Apple ][, but what about the Apple ][ compatibles like the Laser 128 [1]? It doesn't use the same ROM as Apple, they licensed Microsoft Basic directly from Microsoft and then added the missing functionality themselves. I guess someone would have to see how similar it is to a vanilla Apple ][. [1] https://en.wikipedia.org/wiki/Laser_128 https://en.wikipedia.org/wiki/Laser_128
    - duskwuff 3y ago
      From what I can tell from documents like [1], the Laser 128 was very similar (possibly even identical) to an Apple II on a hardware level. It'd have the same issues running at a higher/lower clock speed than it was designed for. [1]: http://www.applelogic.org/files/VTECHL128.pdf http://www.applelogic.org/files/VTECHL128.pdf
    - anyfoo 3y ago
      Again, the answer is almost certainly no, unfortunately. A Laser 128 isn't that fundamentally different to an actual Apple II. In fact, from a wider point of view, they are "almost identical". DRAM needing timely refresh is universal to DRAM itself: It's because DRAM is literally made of a transistor and a capacitor holding your bit, and if you don't access it every so often, that capacitor discharges eventually. The most realistic path to "slow DRAM" would be to replace DRAM with SRAM altogether, which is effectively made of transistors only, and holds its content as long as just power is applied. It's not that hard to replace DRAM with SRAM: Apart from not needing refresh, SRAM behaves similar to DRAM. It's just more expensive (and usually faster, which is also not a drawback), and the DRAM refresh, while not doing anything useful, wouldn't hurt. But as for video output, that's just a consequence of how Apple II's (most microcomputers of that era, actually) video output works: By literally controlling the electron gun in the CRT, with only some analogue electronics in between. The monitor however wants to move the electron beam at a certain speed (or, if you had a fancy Multisync monitor, a set or range of speeds). But even if that wasn't the case, the phosphor on the screen glows only for a short amount of time, so draw your picture too slow, and you will only see small parts of it. The latter can be demonstrated by just pointing a camera at a CRT. In all likeliness, the camera's frequency will be slightly off from the CRT's frequency, so that you capture different parts of the beam's path at each frame, simulating what it would look like if you'd slow down the beam itself: https://pub.mdpi-res.com/sensors/sensors-22-01871/article_deploy/html/images/sensors-22-01871-g010.png?1646125960 https://pub.mdpi-res.com/sensors/sensors-22-01871/article_de... Would it be possible to decouple the video output circuit from the microprocessor's timing? Absolutely! And this is in fact what virtually any modern computers has been doing for many decades by now: Even if you still can find analogue VGA with a CRT, that VGA card had its own clock that is completely independent of the CPU's clock. But that's just not how simple home computers of that era usually operated.
geon 3y ago
Still, you could compile your own custom microsoft basic like Ben Eater did on youtube recently.
- anyfoo 3y ago
  The software is really not an issue. I saw the MOnSter 6502 live running BASIC, and it was MS BASIC as far as I recall. It just wasn't simply hooked up as the CPU of an Apple II or similar.

by dhosek 3y ago

basementcat 3y ago

This is true of the Commodore 64 as the VIC-II chip timing is closely coupled to the NTSC color burst (note below joke about "up-scanning to 60 Hz") Also disk I/O and RS-232 are bit-banged.

anyfoo 3y ago
> Also disk I/O and RS-232 are bit-banged. You could easily slow that down as well. The big problem is really the CRT (and possibly other ICs in the computer that don't like the extreme slowdown). As noted below, if you went through the arduous process of replacing and retuning components to be able to slow the beam down, your phosphor coating is still too fast, and probably doesn't like having the beam passing only slowly over it. (You thought regular burn-in was bad!) However, replace the CRT with something else, like an LCD with some extra buffering circuit, and it could work. Yes, the color burst will be at a much lower frequency as well, but just demodulate color at this lower frequency, then.
- dhosek 3y ago
  Yeah, I’m thinking that the solution would be something that takes the analog monitor signal and uses it to control a digital display.

tombert 3y ago

Again, I know basically nothing about hardware, so this is likely a dumb question: could you conceivably get an oscillator/clock chip that also operates at 1/20th the speed, wire that into the Apple ][, and then wire in this giant CPU?

duskwuff 3y ago
Unfortunately, no. The CPU would work, but memory retention would be unreliable (because the DRAM is now going ~20x too long between refreshes), and the composite video output would fail to display on a monitor (because it's the wrong frequency).
- tombert 3y ago
  Well now I'm wondering; it might not directly run an Apple ][, but what about the Apple ][ compatibles like the Laser 128 [1]? It doesn't use the same ROM as Apple, they licensed Microsoft Basic directly from Microsoft and then added the missing functionality themselves. I guess someone would have to see how similar it is to a vanilla Apple ][. [1] https://en.wikipedia.org/wiki/Laser_128 https://en.wikipedia.org/wiki/Laser_128
  - duskwuff 3y ago
    From what I can tell from documents like [1], the Laser 128 was very similar (possibly even identical) to an Apple II on a hardware level. It'd have the same issues running at a higher/lower clock speed than it was designed for. [1]: http://www.applelogic.org/files/VTECHL128.pdf http://www.applelogic.org/files/VTECHL128.pdf
  - anyfoo 3y ago
    Again, the answer is almost certainly no, unfortunately. A Laser 128 isn't that fundamentally different to an actual Apple II. In fact, from a wider point of view, they are "almost identical". DRAM needing timely refresh is universal to DRAM itself: It's because DRAM is literally made of a transistor and a capacitor holding your bit, and if you don't access it every so often, that capacitor discharges eventually. The most realistic path to "slow DRAM" would be to replace DRAM with SRAM altogether, which is effectively made of transistors only, and holds its content as long as just power is applied. It's not that hard to replace DRAM with SRAM: Apart from not needing refresh, SRAM behaves similar to DRAM. It's just more expensive (and usually faster, which is also not a drawback), and the DRAM refresh, while not doing anything useful, wouldn't hurt. But as for video output, that's just a consequence of how Apple II's (most microcomputers of that era, actually) video output works: By literally controlling the electron gun in the CRT, with only some analogue electronics in between. The monitor however wants to move the electron beam at a certain speed (or, if you had a fancy Multisync monitor, a set or range of speeds). But even if that wasn't the case, the phosphor on the screen glows only for a short amount of time, so draw your picture too slow, and you will only see small parts of it. The latter can be demonstrated by just pointing a camera at a CRT. In all likeliness, the camera's frequency will be slightly off from the CRT's frequency, so that you capture different parts of the beam's path at each frame, simulating what it would look like if you'd slow down the beam itself: https://pub.mdpi-res.com/sensors/sensors-22-01871/article_deploy/html/images/sensors-22-01871-g010.png?1646125960 https://pub.mdpi-res.com/sensors/sensors-22-01871/article_de... Would it be possible to decouple the video output circuit from the microprocessor's timing? Absolutely! And this is in fact what virtually any modern computers has been doing for many decades by now: Even if you still can find analogue VGA with a CRT, that VGA card had its own clock that is completely independent of the CPU's clock. But that's just not how simple home computers of that era usually operated.

geon 3y ago

Still, you could compile your own custom microsoft basic like Ben Eater did on youtube recently.

anyfoo 3y ago
The software is really not an issue. I saw the MOnSter 6502 live running BASIC, and it was MS BASIC as far as I recall. It just wasn't simply hooked up as the CPU of an Apple II or similar.