Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
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Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
33pF improved it but 100pF has fixed it!
Edit - cap in board:
Many thanks to all!
Edit - cap in board:
Many thanks to all!
Last edited by Lardo Boffin on Mon Jan 15, 2024 8:38 am, edited 1 time in total.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
- Flatulentia
- Posts: 93
- Joined: Sun May 14, 2023 3:58 pm
- Location: Cambridgeshire, UK
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
Yay! Thank YOU! I now know roughly what capacitor value I'm likely to need.
ZX81 with ZiLOG Z84 CMOS Z80, 32KB battery-backed Toshiba 55257 SRAM with charge status LED, Wilf's "Why Wait?" mod and switch-mode 5V regulator. 50/60Hz mode switch, composite video output with Zigg's back porch mod and 1080p60 HDMI output.
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
Just a question:Lardo Boffin wrote: ↑Sat Jun 03, 2023 8:48 pm 33pF improved it but 100pF has fixed it!
Many thanks to all!
IMG_2144.jpeg
IMG_2143.jpeg
I see DOGCATCHER. How did you get that version?
The original is MAKE A SHIT and the version DOGCATCHER was intended to be used for a video only if the name MAKE A SHIT could be to offensive.
Did I release a wrong version?
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- Posts: 2160
- Joined: Sat Nov 26, 2016 2:42 am
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
From here:dr beep wrote: ↑Sat Jun 03, 2023 9:47 pmJust a question:Lardo Boffin wrote: ↑Sat Jun 03, 2023 8:48 pm 33pF improved it but 100pF has fixed it!
Many thanks to all!
IMG_2144.jpeg
IMG_2143.jpeg
I see DOGCATCHER. How did you get that version?
The original is MAKE A SHIT and the version DOGCATCHER was intended to be used for a video only if the name MAKE A SHIT could be to offensive.
Did I release a wrong version?
viewtopic.php?t=3124
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
- 1024MAK
- Posts: 5101
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
In answer to the earlier question about the type of SRAM chip used, it’s because the modern chips have too quick an access time. The capacitor maintains the control signal for a faction longer. Hence the SRAM continues to output data for a bit longer, allowing it to be read. The hi-res timing appears to be more timing critical than the normal display routine.
The resistor in the other modification is only needed for configurations where you are trying to use battery backup.
Mark
The resistor in the other modification is only needed for configurations where you are trying to use battery backup.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
Ah.... that's true.Lardo Boffin wrote: ↑Sat Jun 03, 2023 9:54 pmFrom here:dr beep wrote: ↑Sat Jun 03, 2023 9:47 pmJust a question:Lardo Boffin wrote: ↑Sat Jun 03, 2023 8:48 pm 33pF improved it but 100pF has fixed it!
Many thanks to all!
IMG_2144.jpeg
IMG_2143.jpeg
I see DOGCATCHER. How did you get that version?
The original is MAKE A SHIT and the version DOGCATCHER was intended to be used for a video only if the name MAKE A SHIT could be to offensive.
Did I release a wrong version?
viewtopic.php?t=3124
It was a small demogame and it is not MAKE-A-SHIT from the 1K hires series.
- Flatulentia
- Posts: 93
- Joined: Sun May 14, 2023 3:58 pm
- Location: Cambridgeshire, UK
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
I'll correct my saved copy of the schematic then as it says that resistor is for HRG8 and the other one is for battery backup. Thanks.
ZX81 with ZiLOG Z84 CMOS Z80, 32KB battery-backed Toshiba 55257 SRAM with charge status LED, Wilf's "Why Wait?" mod and switch-mode 5V regulator. 50/60Hz mode switch, composite video output with Zigg's back porch mod and 1080p60 HDMI output.
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
I like your BBC owl coaster peeking out in the photo!
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- Posts: 2160
- Joined: Sat Nov 26, 2016 2:42 am
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
The kids made it for me. You arrange loads of beads on a grid and then iron it to melt them together.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
- Flatulentia
- Posts: 93
- Joined: Sun May 14, 2023 3:58 pm
- Location: Cambridgeshire, UK
Re: Internal 16K RAM mod doesn’t quite work with Dr Beep hires games
This is weird!
RudeDogRetros make the same mod I'm using (minus battery backup) as a plug-in module and that has a link that appears to either connect/disconnect that 10K resistor to enable/disable HRG8. This is the second commercial product I've found with the 10K resistor claiming it gives HRG8 capability.
Is everyone just copying it blindly and getting it wrong?
https://rudedogretros.co.uk/product/zx8 ... ade-board/
RudeDogRetros make the same mod I'm using (minus battery backup) as a plug-in module and that has a link that appears to either connect/disconnect that 10K resistor to enable/disable HRG8. This is the second commercial product I've found with the 10K resistor claiming it gives HRG8 capability.
Is everyone just copying it blindly and getting it wrong?
https://rudedogretros.co.uk/product/zx8 ... ade-board/
ZX81 with ZiLOG Z84 CMOS Z80, 32KB battery-backed Toshiba 55257 SRAM with charge status LED, Wilf's "Why Wait?" mod and switch-mode 5V regulator. 50/60Hz mode switch, composite video output with Zigg's back porch mod and 1080p60 HDMI output.