ZX80 8K ROM original keyboard layout

[sirmorris]

Seriously? No restore line number eh. That's weird.

[poglad]

Well I've emailed Steve Vickers to find out whether he has any memory of these little details. You never know, eh?

[poglad]

Okay, here's what Steve Vickers had to say:

I don't have the original ROM, and can't remember the answers to your specific questions. The fundamental problem at the time was that the ROM was full with less than a dozen bytes to spare, and we had to be fairly ruthless about dropping features that could be programmed in Basic. You can see, for instance, DRAW given in the manual. You are right that for the Spectrum we more or less just reinstated the code we had dropped.

Now I must have inadvertently included some of his space optimizations from the ZX81, as I currently have more than a dozen bytes spare. However, it obviously takes up more space to have the line number and multiple-variable handling in RESTORE and READ, and those were present in the Spectrum version, so it seems to me that probably we should include them in the ZX80 version too. Anything that contributes to the space problems they had is probably original! I also notice that the Sync magazine is incorrect in at least one other place - it doesn't show NEXT as taking a variable. So we should probably not treat it as 100% perfect.

The remaining doubt in my mind concerns the font. Vickers had no memories to offer, unfortunately. The question is, did Vickers change wider font of the ZX80 into the square font of the ZX81 at this point in the ROM's development, or subsequently?

What he does say is the following:

I was taken on to write the floating point maths pack, and I ended up doing most of the adaptation and new code for the ZX81 and Spectrum.

Now, if your remit is to expand the ZX80's maths package, it seems doubtful that you'd set about redesigning its font. However, the appearance of the characters would become important later when the ZX Printer routines were added, if it was felt that the printed characters would look better with a redesign. On the other hand, Vickers already had to at least re-order the character set at this stage so that his PLOT routine would work, as the quote character was in amongst the mosaic characters. Would he have used that as an excuse to redesign the font?

Personally, I'm now inclined to think that the ZX80 font survived until the ZX Printer testing, and was redesigned in order to make the print-outs look better. What do you all think?

It looks like, with a reinstated RESTORE line number, reinstated READ variable list, and possibly reinstated ZX80 font - we could have our ROM recreated.

Paul

[sirmorris]

I think you're on to something. I love the fact that Mr. Vickers responded Not to mention the fact you wrote in the first place!

[poglad]

Well I've updated the ROM file on my share folder - it now has the above changes, including the font. Give it a spin when you have time!

[Paul]

I tried the actual version of your rom with EightyOne.
Works nice. This font looks far better.
Restore with line number works great.
Save does not go into the tape manager. I wonder why?
Kind regards
Paul

[poglad]

Probably because the SAVE/LOAD entry points have moved. I'll see if they're far out, I can probably move them a few bytes either way so that they line up with where they were in the ZX81 ROM. There could be several emulators that detect it that way, so it would be good to be able to work with them.

With the wider font, it now actually looks like a ZX80 ROM doesn't it!

[poglad]

Ah, I've just had a look at EO and it seems that several ROM entry points are trapped to support the saving and loading. For the ZX80, it will expect the routines to follow the layout of the original ZX80 routines but of course this new ROM follows the ZX81 layout as it supports saving with a filename. So EO would probably have to have some extra cases added in order to recognize this ROM - perhaps sirmorris knows more about that?

Ditto for getting it to show the updated keyboard overlay when you press F1.

[sirmorris]

I haven't touched EO for a while now but I suspect it's possible. I'll PM you.

[poglad]

Okies. I've looked at the (out of date?) EO source online and I don't think it would be difficult to add support for it alongside the other ROMs - if it's wanted, of course. I still don't know if the ROM even works on real hardware!