ZX80/ZX81 core [new]

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slingshot
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ZX80/ZX81 core [new]

Post by slingshot »

Just for exercising FPGA programming, I've created a new ZX80/ZX81 core based on Sorgelig's much improved T80. Feel free to try out:
https://github.com/gyurco/ZX8X_MiST
RobeInie
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Re: ZX80/ZX81 core [new]

Post by RobeInie »

Thanks !!

I will try next week, when I arrive at home,
Nice to see turbo loading in features !
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Re: ZX80/ZX81 core [new]

Post by squid4 »

Great to see the ZX81 getting some more love! What is the rom supplied with this, doesn't look like a UK ZX81 one to me (actually looks to be ZX80 only). Tried using an original ZX81 ROM but it doesn't work - from here https://k1.spdns.de/Vintage/Sinclair/80 ... ZX81/ROMs/

Update: Figured it out, start it, F12 change to ZX81 and 16K then select reset. Starts as ZX81 then. Doesn't save the settings so it needs to be done each time it is started. Can it default to ZX81 16k instead of ZX80? Tried Mazogs and it loads instantly and works great! Also nolimits.p demo works well.
DanyPPC
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Re: ZX80/ZX81 core [new]

Post by DanyPPC »

Thanks for this new core :cheers:
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

Figured it out, start it, F12 change to ZX81 and 16K then select reset. Starts as ZX81 then. Doesn't save the settings so it needs to be done each time it is started. Can it default to ZX81 16k instead of ZX80? Tried Mazogs and it loads instantly and works great! Also nolimits.p demo works well.
You can save the setting as in other cores: press RIGHT at the OSD, then choose "Save settings".
desUBIKado
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Re: ZX80/ZX81 core [new]

Post by desUBIKado »

Thank you slingshot for your core. It's great see new cores for MiST

I have tried your core a little and I've saw a visual issue with the first lines of the screen
M800_20180817_212303.jpg
M800_20180817_212045.jpg
These images are on 15 KHz RGB output, but I get the same result with VGA output, on 50Hz or 60 Hz, with my Mistica FPGA16.
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slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

desUBIKado wrote: I have tried your core a little and I've saw a visual issue with the first lines of the screen
There's a 2 clock cycle skew in the HSync counter at the first line, which I don't know if it's a problem with the T80, my ZX81 implementation, or it's just there with the original hardware, too. For example, it is hardly noticeable on my TV, but with scandoubling it's very obvious.
Also there are conflicting informations on the net when the HSync counter should be synchronized, Grant Searle's site says it's synced to INTACK, but other places says it's synced to VSync. So if somebody has more information about it, please share. Currently it's synced to INTACK.
Sorgelig
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Re: ZX80/ZX81 core [new]

Post by Sorgelig »

slingshot wrote:if it's a problem with the T80,
Apply my recent DI_Reg fix from SAM Coupe core - it may help.
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

So released a new version, with the HSync signal shifted by two clock cycles, which seems to solve (or hide?) the problem.
Also added 64k RAM pack support, so the great remake:
https://problemkaputt.de/hero.htm
can be played!
If it is not displayed with scandoubler, try setting the frequency to 60Hz.
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Re: ZX80/ZX81 core [new]

Post by squid4 »

Last good one on my Sony CRT 15khz was zx8x_20180815.rbf. Any after that the picture is very dark.
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

squid4 wrote:Last good one on my Sony CRT 15khz was zx8x_20180815.rbf. Any after that the picture is very dark.
I fixed this (at least it looks good on my TV). Please try today's release.
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Re: ZX80/ZX81 core [new]

Post by squid4 »

slingshot, Wow! you've fixed it. Skew problem, that also affected the older core I worked on, has been fixed and the video looks perfect on SCART - looks better than my real ZX81!

With your permission I'll replace the old core on the official Mist website with this core.
Last edited by squid4 on Mon Aug 20, 2018 8:21 am, edited 1 time in total.
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

Of course you can put it on the main MiST binaries site.
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

Released a new version:

- Joystick support (keys 67890)
- AY sound chip (with ZON X-81 compatible ports)

https://github.com/gyurco/ZX8X_MiST/blo ... 180825.rbf
NML32
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Re: ZX80/ZX81 core [new]

Post by NML32 »

Nice job on the core.
Thanks for adding joystick support.
desUBIKado
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Re: ZX80/ZX81 core [new]

Post by desUBIKado »

Glad to see the first line issue is fixed. Great job.
20180826_113853.jpg
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slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

Thanks to Sorgelig, he fixed the NMI cycle of the T80, so now the core is cycle perfect. Still has some hsync shift in FAST mode (only in 2 lines), but this seems to be present on the original machine, too.
New release:
https://github.com/gyurco/ZX8X_MiST/blo ... 180828.rbf
slingshot
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Re: ZX80/ZX81 core [new]

Post by slingshot »

Just added CHR128 character board support.
Changed the releases structure, new release is here:
https://github.com/gyurco/ZX8X_MiST/releases
DanyPPC
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Re: ZX80/ZX81 core [new]

Post by DanyPPC »

Many thanks for this update !
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