Would it be possible to run H4th on a ZX80?

[Moggy]

As the title suggests, seeing as the ZX81 ROM chip can be dropped into a ZX80 and work off the bat as it were,if a suitable EPROM could be found or using the modern 8k chip replacement RWAP supplies would H4th run as it does on the ZX81 albeit in fast mode or are there other hardware constraints?

My logic being if one drop in solution works without alteration then surely all other would behave in a likewise fashion?

[Paul]

Only if the ROMs work in FAST Mode in all respects.

[Moggy]

Thanks for that Paul, almost makes me want to try it!

EDIT.

just tried the ZX81 ROM with Eighty One set as a ZX80 and that works ok however when I tried the H4th ROM I just get a blank screen, ah well never mind.

[Paul]

Hi Moggy,
I started H4th for the first time in mylife. On EightyOne.
It starts and works.
if I enter FAST the display disappers. it still seems to work because when I enter SLOW the display reappears.

If there is no no Display at all in FAST mode then it can't work in a ZX80 of course.

Thats what I meant with "in all respects"

The editor, inputs, pause etc. have to be working in fast mode.

I have no Idea if this is true for any available ROM. Maybe Azmic?

[dr beep]

Paul means in FAST mode that regularly the display must be called. unlike the ZX81 on the ZX80 this is not intruptdriven.

[Moggy]

Hi Moggy,
I started H4th for the first time in mylife. On EightyOne.
It starts and works.
if I enter FAST the display disappers. it still seems to work because when I enter SLOW the display reappears.

If there is no no Display at all in FAST mode then it can't work in a ZX80 of course.

Thats what I meant with "in all respects"

The editor, inputs, pause etc. have to be working in fast mode.

I have no Idea if this is true for any available ROM. Maybe Azmic?

Did you have Eighty One in ZX80 or ZX81 mode?

In ZX80 mode it will happily use the ZX81 ROM but when Eighty One is in ZX80 mode all I get is a blank screen when I select the H4th ROM.

[Paul]

It was in ZX81 mode.
The blank screen is all you get in FAST-Mode

[Moggy]

The point I'm making or question I'm asking is simply will the H4th ROM work on a ZX80 not ZX81 which we all know it does, and rather than burn an EPROM I tried using Eighty One in ZX80 mode with the H4th ROM and just got a blank screen and unresponsive keyboard.

My logic being that if a ZX81 ROM can be just dropped into a ZX80 and work then why cannot any other ROM meant for a ZX81 be used in a similar fashion?

FAST mode doesn't come into it as far as I can tell so if a ZX81 ROM just works on a ZX80 and also the Azmic ROM too, then why not the H4th ROM?

This is the question I'm asking but nobody seems to grasp my meaning and I cannot make it any simpler sadly so if the problem is too difficult I'll leave it at that.

[Paul]

Dear friend, basically a ZX80 is a ZX81 without SLOW mode.
We all know ist the other way round.
So a ZX80 is always in FAST mode and needs a special SLOW device in order to fully use the ZX81 ROM.
If there is a ROM whose Editor (and INPUT and PAUSE) works in FAST mode, then it will work with the ZX80 as well.
The ZX81 ROM was built with the ZX80 in mind. Therefore there is a "fallback" programmed that runs in FAST mode on a ZX80.
The AZMIC ROM was built without the ZX81 in mind. That's why it doesn't benefit from the possibilities of the ZX81.
The ZX81 tries to activate SLOW after the initial Setup (RAM test, initialize the system variables etc.)
When SLOW has no effect it simply stays in FAST.

H4th ROM is only designed for SLOW mode Programming.
It allows the KEYWORDS SLOW and FAST, but it lacks the Display when in INPUT, PAUSE or when using the editor.
I am not sure, but I think H4th works fine ZX80 mode, but simply doesn't show anything.
Does H4th allow using the printer?
Please try using H4th blind and use the Printer if possible.
Or does it support writing to reset resident RAM?
Maybe we can check in EO by inspecting the memory?

[Moggy]

Dear friend, basically a ZX80 is a ZX81 without SLOW mode.
We all know ist the other way round.
So a ZX80 is always in FAST mode and needs a special SLOW device in order to fully use the ZX81 ROM.
If there is a ROM whose Editor (and INPUT and PAUSE) works in FAST mode, then it will work with the ZX80 as well.
The ZX81 ROM was built with the ZX80 in mind. Therefore there is a "fallback" programmed that runs in FAST mode on a ZX80.
The AZMIC ROM was built without the ZX81 in mind. That's why it doesn't benefit from the possibilities of the ZX81.
The ZX81 tries to activate SLOW after the initial Setup (RAM test, initialize the system variables etc.)
When SLOW has no effect it simply stays in FAST.

H4th ROM is only designed for SLOW mode Programming.
It allows the KEYWORDS SLOW and FAST, but it lacks the Display when in INPUT, PAUSE or when using the editor.
I am not sure, but I think H4th works fine ZX80 mode, but simply doesn't show anything.
Does H4th allow using the printer?
Please try using H4th blind and use the Printer if possible.
Or does it support writing to reset resident RAM?
Maybe we can check in EO by inspecting the memory?

Excellent Paul I grasp what you are saying and will try what you say about the printer.

Many thanks Paul much appreciated.