TO Grauw (and others, of course): YASVL

ページ 1/2
| 2

By PingPong

Prophet (3885)

PingPong さんの画像

04-01-2022, 01:41

OK, let's explain the acronym:
Y et
A nother
S tupid
V dp
Limitation

During investigation in r5 and r11 vdp registers (SAT attribute table address) i've found some 'peculiarities' of bits usage from the vdp when working in sprite mode 1 or 2.

I must admit, that after more than 30 years the vdp keep surprising me in how they managed to setup not needed behaviours that finally turns out to be another limitations.
After i've saw how lower bits in r5 are used in r5, another thing surprised me. the wiki say that the higher bits (> upper 64K range) are only used in screen 7-8.

I hope this is a documentation mistake, because otherwise this would mean that , if i need, i cannot set the SAT on the upper 64K (in a 128K vram machine, of course), when working, for example in screen 5, leaving page 0-1 free from sprite data.
I think this behaviour is unnecessary, why the VDP should mask out as zero those higher bits in screen 4-5-6? if i want to be on the lower 64K it's my responsability to keep them 0. By contrast, by forcing them to be 0 you remove me some flexibility in address placement.

Can anyone confirm this is true on a real machine? I CANNOT BELIEVE THIS. I CANNOT BELIEVE, REALLY. Maybe yamaha designers asked Kuttag for some stupid idea? oO :-( Question Crying Crying Crying

ログイン/登録して投稿

By Grauw

Ascended (10560)

Grauw さんの画像

04-01-2022, 09:36

PingPong wrote:

After i've saw how lower bits in r5 are used in r5, another thing surprised me. the wiki say that the higher bits (> upper 64K range) are only used in screen 7-8.

That’s not true, there is no such limitation on the high bits in r11, they can be used in any screen mode.

By Sandy Brand

Champion (276)

Sandy Brand さんの画像

04-01-2022, 10:57

Yes I can confirm. I have lots of sprite attribute tables in screen 5 page 3 and that all works as expected.

By PingPong

Prophet (3885)

PingPong さんの画像

04-01-2022, 11:17

then i think the wiki should be corrected as it does reports this 'feature'

By Pippo

Hero (521)

Pippo さんの画像

04-01-2022, 11:45

I kindly confirm as well: The sprites tables can be used anywhere. Smile

By Pippo

Hero (521)

Pippo さんの画像

04-01-2022, 11:52

It seems Yamaha Designers are not stupid, maybe others....

By PingPong

Prophet (3885)

PingPong さんの画像

04-01-2022, 15:11

I've suspected that docs were incorrect. However given the others stupid quirks on VDP (SCT being related to plane instead of pattern no, the stupid Y coordinate that gives trouble when dealing with vert scroll register, the EC bit at a scanline level) being doubtful it is understandable ...

By Pippo

Hero (521)

Pippo さんの画像

04-01-2022, 16:15

PingPong wrote:

I've suspected that docs were incorrect. However given the others stupid quirks on VDP (SCT being related to plane instead of pattern no, the stupid Y coordinate that gives trouble when dealing with vert scroll register, the EC bit at a scanline level) being doubtful it is understandable ...

I see.
But, it is good habit to think carefully before talking. Smile

By PingPong

Prophet (3885)

PingPong さんの画像

04-01-2022, 19:16

68 / 5.000
Risultati della traduzione
I hope I don't have to suffer criminal consequences for my claims

;-)

By Pippo

Hero (521)

Pippo さんの画像

04-01-2022, 21:42

PingPong wrote:

68 / 5.000
Risultati della traduzione
I hope I don't have to suffer criminal consequences for my claims

;-)

However, I always think you are in the wrong forum. Smile

By Pippo

Hero (521)

Pippo さんの画像

04-01-2022, 22:23

I really think I am in the wrong forum too.
Due to the moderator could take action, I have to close the discussion.

ページ 1/2
| 2