RGB mod for TMS99xx based computers

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1024MAK
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Location: Looking forward to summer, in Somerset, UK

Re: RGB mod for TMS99xx based computers

Post by 1024MAK »

gunrock wrote: 12 Feb 2021 11:54 I'm guessing that people have seen:

tms-rgb-board.png

It's a RGB modification for TMS99xx machines. It actually mentions the Memotech MTX on it's landing-page at:

https://tms-rgb.com/

It's quite pricey if you buy it ready to install, about 32 EUR from Ireland (plus postage). Has anybody seen it or tried it? Or does everybody only run CP/M? :lol: :lol:
Interesting. Unfortunately in BREXIT Britain, we can’t currently order it from the Irish seller, as they are currently In the process of adapting to the new trading arrangements :(

Mark
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gunrock
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Re: RGB mod for TMS99xx based computers

Post by gunrock »

I know Mark, I have the issue the other way, goods from the UK over 9.40 GBP (at today's rates) incur Danish VAT at 25% and depending on the item, customs charges.

Add to that the PostNord (Denmark & Sweden's state-run postal service) handling feed of 160 DKK (18.80 GBP at today's rate), it's excruciating.
Tony Brewer
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Re: RGB mod for TMS99xx based computers

Post by Tony Brewer »

Bill B wrote: 12 Feb 2021 16:04 The issue is the difference between 50Hz and 60Hz.

Games use the VDP interrupt to update the VDP only when it is not refreshing the screen. Since the Propeller is running at a different refresh rate, it frequently draws the screen partly through an update, resulting in display artifacts such as spurious sprites.

To do better, the Propeller would need to either synchronise with the VDP interrupt (tricky), or completely replace the VDP, in which case it would need to do sprite collision detection and generate the frame interrupt.

Some TV/Monitors (mine for example) will accept 640x480 VGA at 50Hz rather than 60Hz.
To synchronise a Propeller, how about putting /VDPINT on the system bus by soldering a wire (must be yellow) from VDP pin 16 or CTC pin 23 to A25 on J10? This assumes LK12 is missing.
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Dave
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Re: RGB mod for TMS99xx based computers

Post by Dave »

Tony Brewer wrote: 24 Feb 2021 15:16 To synchronise a Propeller, how about putting /VDPINT on the system bus by soldering a wire (must be yellow) from VDP pin 16 or CTC pin 23 to A25 on J10? This assumes LK12 is missing.
The obvious downside of that is that it would stop the board from being "plug & play", most folks who have bought stuff from me wouldn't have the confidence or inclination to solder wires onto the MTX - however easy that might be. (I suspect that many people wouldn't be keen on the RGB Mod board for the same reason.)

For others though, I guess that soldering a single wire wouldn't be too much of a barrier

regards
Dave
Tony Brewer
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Re: RGB mod for TMS99xx based computers

Post by Tony Brewer »

Dave wrote: 24 Feb 2021 17:26
Tony Brewer wrote: 24 Feb 2021 15:16 To synchronise a Propeller, how about putting /VDPINT on the system bus by soldering a wire (must be yellow) from VDP pin 16 or CTC pin 23 to A25 on J10? This assumes LK12 is missing.
The obvious downside of that is that it would stop the board from being "plug & play", most folks who have bought stuff from me wouldn't have the confidence or inclination to solder wires onto the MTX - however easy that might be. (I suspect that many people wouldn't be keen on the RGB Mod board for the same reason.)

For others though, I guess that soldering a single wire wouldn't be too much of a barrier

regards
Dave
One alternative with no soldering (for the end-user) might be to remove the CTC and replace it with a thin PCB to which a CTC is soldered or in a low-profile socket ideally. PCB also has a pin to connect /VDPINT to a Propeller board via a flying lead. Headroom permitting.

Or leave CTC as is and clip a flying lead onto pin 23.

Or supply replacement CTC with lead soldered to pin 23.
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Dave
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Re: RGB mod for TMS99xx based computers

Post by Dave »

Ah, some good ideas there, one of those would do the trick
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