OUTI takes 1 extra cycle on Turbo machine

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By Manuel

Ascended (15756)

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27-07-2018, 23:39

There might be some useful info here: https://github.com/openMSX/openMSX/issues/989

By Eugeny_Brychkov

Paragon (1097)

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28-07-2018, 00:41

Anyone tried to play with signals ICE (I) and WAIT (I/O)? There're jumpers J1 and J2 on the circuit diagram of the TurboR-ST. Removing J2 and J1 must stop Z80 getting wait states from S1990 (hopefully ICE is having pull down resistor so that it is inactive when jumper is removed, and WAIT acts as input). GT has ICE jumper only (J303, however it seems to be physically shorted on the board).

(I hope I interpreted Kanji properly Smile )

By MsxKun

Paladin (922)

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28-07-2018, 12:01

Eugeny_Brychkov wrote:

Anyone tried to play with signals ICE (I) and WAIT (I/O)? There're jumpers J1 and J2 on the circuit diagram of the TurboR-ST. Removing J2 and J1 must stop Z80 getting wait states from S1990...

If for any reason I'd open my TR to do that I'd probably faint Tongue

By gdx

Prophet (3041)

gdx's picture

28-07-2018, 15:33

J2 and J1 jumpers are for video signal.

If J2 is shorted and J1 cut then YUV + Csync.
If J1 is shorted and J2 cut then Csync only.

It seems usefull for a few monitors.

https://m.blog.naver.com/overrich/220858124558

By Grauw

Ascended (8457)

Grauw's picture

28-07-2018, 15:36

On the GT the J1 and J2 jumpers are related to the change they made to make room for the MIDI connectors, removing the composite output plug and instead putting it on the RGB connector in stead of CSYNC. You can use them to undo that. See 2.3) Panasonic FS-A1GT jailbar fix. Works really well btw, my turboR GT’s RGB output is now jailbar-free.

But although I haven’t looked at the ST’s schematics while saying this, I reckon on the ST these jumpers probably have a different function. It wouldn’t make much sense to offer that csync/composite choice on the ST, given that all the connectors are still in place.

I’m also curious about whether the S1990 registers have any secrets left to uncover (such as disabling VDP wait, one can only dream), certainly their functions are not fully known.

By Eugeny_Brychkov

Paragon (1097)

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28-07-2018, 16:12

Grauw wrote:

I’m also curious about whether the S1990 registers have any secrets left to uncover (such as disabling VDP wait, one can only dream), certainly their functions are not fully known.

So let me repeat...

1. is there any research on it - better more or less complete?
2. Anyone having Turbo is willing to make own research (with my assistance)? Ideally the person having GR8NET because it has good way to test for wait states - playing video;

In general information provided in this thread leads me to suspect there's no such secret as wait state disable or adjust, otherwise there would be no A/B/C versions of the T9769 chip and adjustment would be made on BIOS/software/firmware level. However probability of some secrets is still high, as there seem to be a lot of unexplored room in register space!

By Grauw

Ascended (8457)

Grauw's picture

28-07-2018, 16:29

1. What I know is here.
2. I would like to do experiments at some point in the future but not now.

Eugeny_Brychkov wrote:

In general information provided in this thread leads me to suspect there's no such secret as wait state disable or adjust, otherwise there would be no A/B/C versions of the T9769 chip and adjustment would be made on BIOS/software/firmware level. However probability of some secrets is still high, as there seem to be a lot of unexplored room in register space!

For sure! I agree though that probably there’s no such thing as a wait disable, we would be extremely lucky if someone found there was.

By gdx

Prophet (3041)

gdx's picture

28-07-2018, 16:37

I don't think that it has any effect but try with the register 25 (bit WTE) of the VDP.

By Grauw

Ascended (8457)

Grauw's picture

28-07-2018, 20:32

You can save yourself the time, it has no effect, WAIT output pin is not connected.

By the way, going back to the topic starter;

Eugeny_Brychkov wrote:

Recently I was told, and actually shown, that GR8NET video player performs worse on Turbo machine than on MSX2+ machine in terms of performance - on Turbo machine it is slower and audio hiccups.

To be clear, most MSX2+ machines also have these wait cycles, even two of them:

0 cycles: Sony HB-F1XDJ, Sony HB-F1XV
1 cycle: Panasonic FS-A1WSX, Panasonic FS-A1ST, Panasonic FS-A1GT, Aucnet NIA-2001
2 cycles: Panasonic FS-A1FM (MSX2), Panasonic FS-A1FX, Panasonic FS-A1WX, Panasonic FS-A1WSX, Sanyo PHC-35J, Sanyo PHC-70FD, Sanyo PHC-70FD2, Al Alamiah AX-370

By Eugeny_Brychkov

Paragon (1097)

Eugeny_Brychkov's picture

28-07-2018, 21:13

Grauw wrote:

0 cycles: Sony HB-F1XDJ, Sony HB-F1XV

Sony HB-F1XV machine is proven to play video properly. As well as GR8BIT with configurable wait state engine Smile

Do other machines also use T9769 chip?

Grauw wrote:

To be clear, most MSX2+ machines also have these wait cycles, even two of them:

And I guess it is not defined in the MSX standard... One more reason why MSX faded away from the market - companies started to make/release "custom" hardware competing with PC. This is very small deviation or variation on the design, but severe obstacle for using machine for RTOS and real time tasks like audio and video.

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