Sinclair ZX80 / ZX81 / Z88 Forums

bwinkel67 wrote: ↑Mon Feb 13, 2023 10:28 pm I'm in the US...I wonder if that's adds any difference. It's running on 9V DC...would it be a 50 vs 60 Hz issue?

Very unlikely, as all practical mains frequency AC components should be removed by the combination of the smoothing (filter) capacitor in the PSU and the 7805 voltage regulator on the computer board.

Mark

1024MAK wrote: ↑Tue Feb 14, 2023 1:13 am Very unlikely, as all practical mains frequency AC components should be removed by the combination of the smoothing (filter) capacitor in the PSU and the 7805 voltage regulator on the computer board.

But don't the ZX81 and TS1000 run at slightly different speeds? I've done timings when compared to my ZXSimulator and one runs slightly faster. I though it had to do with the clock signal since one is NTSC and the other is PAL.

bwinkel67 wrote: ↑Tue Feb 14, 2023 7:41 pm

1024MAK wrote: ↑Tue Feb 14, 2023 1:13 am Very unlikely, as all practical mains frequency AC components should be removed by the combination of the smoothing (filter) capacitor in the PSU and the 7805 voltage regulator on the computer board.

But don't the ZX81 and TS1000 run at slightly different speeds? I've done timings when compared to my ZXSimulator and one runs slightly faster. I though it had to do with the clock signal since one is NTSC and the other is PAL.

I don't think in the '80s special tapes were released in America because european tapes wouldn't load.
During loading intrupts are disabled, so timing should be the same.

bwinkel67 wrote: ↑Tue Feb 14, 2023 7:41 pm But don't the ZX81 and TS1000 run at slightly different speeds? I've done timings when compared to my ZXSimulator and one runs slightly faster. I though it had to do with the clock signal since one is NTSC and the other is PAL.

In FAST mode, they both execute code at the same speed. They both use a 6.5MHz resonator (the Z80 clock speed being half of this, hence 3.25MHz nominal).

In SLOW mode, if using the normal BASIC system, a board configured for a U.S.A. TV system (525 line, 60Hz, NTSC) draws the screen more often, so there is less time for the Z80 to run ‘user’ programs, compared to a board configured for a European TV system (625 line, 50Hz) (not PAL, as PAL is referring to a colour TV standard, which came along after the monochrome TV standard).

This is all completely independent of what the local mains frequency is. All the timing is derived from the 6.5MHz resonator.

As the BASIC system does not run in SLOW mode, but runs in FAST mode when saving or loading, it should not make any difference.

The difference in configuration, is the fitment or not of resistor R30. It’s not fitted for European boards. A ten ohm resistor is fitted for U.S.A. boards. However, please note that although the Sinclair BASIC detects if this resistor is fitted or not fitted and uses this information, a machine code program that generates its own display may or may not do the same.

Mark

Here we are talking about the ZX81/TS1000. Could this, though impact a 3rd party software that is re-creating the ZX81/TS1000 loader on the 48K Spectrum? As I said, the audio files load just fine, generated by EightyOne (ZX81) on my actual TS1000, but when trying ZX Slowloader on actual 48K Spectrum, it cannot pick up the signal (whereas it does easily on emulated (EightyOne) 48K Spectrum?

I honestly can’t work out why your real ZX Spectrum loads Spectrum software okay, but not ZX81/TS1000 software when running the Slowloader program. When it works okay under emulation.

Hence why I suggested you try with a real ZX81/TS1000 tape to see if that works.

The other thing that would help, would be if someone else could try, and then report back on what results they got. Unfortunately, work, plus a new puppy are taking up most of my time. So I currently am not in a position to try this myself anytime soon.

Mark

A silly question perhaps but I'll ask it anyway as it hasn't been mentioned.

You only mention software so do you have the hardware interface that accompanies it and is needed for it to work ?

Hardware?

Mark

Yup summat plugs into the expansion port apparently (article to follow)

slowloader I used was software only and worked good in 1983.