Sinclair ZX80 / ZX81 / Z88 Forums

Andy Rea wrote:CLCKFREQ.P new record (for me anyway)

frames taken: 194
speed 960.3%
freq 7.68Mhz

this is 20Mhz turbo mode, Wilf's Why wait circuit (coded in the CPLD), and the SG81_b rom as posted by Zsolt.

now then.... how do i get to 1000%...

Regards Andy

does this count.... even thought CLCKFREQ would report a normal speed ZX81... this sucker runs 10X faster than normal including video generation... which is then fed to a VGA-submodule...

https://www.youtube.com/watch?v=Y9ZIVzMZvJE

Andy

Meh, doesn't count IMHO.

Although ... In Mahlerts I asked many people to define what a zeddy was. I think the general answer was - if you can run any piece of ZX81 software on there unaltered then it's a zeddy. I suppose this FPGA implementation technically passes that test.

For me though - it has to have (at least) 4 chips. End of.

C

sirmorris wrote: For me though - it has to have (at least) 4 chips. End of.

C

For me, it has to be slow to be a real Zeddy.

In fact any hardware modification is allowed for me except increasing the clock frequency.
So 3.25 MHz for Z80 is a must, every hardware mod making it faster is good, any software mod is good same (SG81 rom).

Hello again,

Since the "Towers of Hanoi" i dealt with a lot of BASIC programming - again - but...

Because of this topic I returned to the machine code, and the first results are in the attachment.
Enjoy,
Zsolt

Wow! So it is now possible to get 25,5% more speed from our Zeddies just by replacing the original ROM.
This without modding any hardware, breathtaking!

Hi,

Do you remember this BASIC trick: nnnn POKE 16418,0 (where the 'nnnn' is a BASIC line number) ?
Using this trick, you can write on entire screen - the zeddy accepts the PRINT AT 23,xx

But What about PLOT and SCROLL
The PLOT origin (0,0) does not change - see on the picture below - the SCROLL destroys the system.
You can find in the attachment:

SG81_d.rom - the patched ROM
SG81_d.asm, newSCROLL.asm, newPLOT.asm, newPOINTERS.asm, new_e-to-fp.asm - the source codes
bottomlines.p, print_at23.p, plot48.p, scroll24.p, neg-pr-pl.p - the examples

The latest source code (new_e-to-fp.asm) is a little step to solve the zeddy's "printing a floating point number" problem - see this topic.

Regards,
Zsolt

EDIT: the latest version is here - the plot-mod was removed because of the backward compatibility.

Does that also mean, that e. g.
POKE 16418,10
sets the origin for PLOT 10 lines up?

And does SCROLL then only scrolls up the first 14 lines and does not touch the lower 10 lines?
If yes, that could be used to scroll parts of the screen, maybe useful in games, when POKE 16418 is set to several values depending of the state of the game ...

Siggi

siggi wrote:Does that also mean, that e. g.
POKE 16418,10
sets the origin for PLOT 10 lines up?
And does SCROLL then only scrolls up the first 14 lines and does not touch the lower 10 lines?

Exactly (btw. the latter effect was available with the original rom also)
Regards,
Zsolt

I loaded SG81 into my ZXNU and ran the POKETEST. Works fine
AFAIK the final POKE 16418,2 is not necessary. I never used that in my programs, after I had used the full screen. It seems to be set to default at the end of the program.

Siggi

Andy Rea wrote:CLCKFREQ.P new record (for me anyway)

frames taken: 194
speed 960.3%
freq 7.68Mhz

this is 20Mhz turbo mode, Wilf's Why wait circuit (coded in the CPLD), and the SG81_b rom as posted by Zsolt.

now then.... how do i get to 1000%...

Regards Andy

Did you already try the latest SG81 Rom?

Siggi