SymbOS MSX multitasking operating system - help needed!

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By Prodatron

Paragon (1788)

Prodatron's picture

01-01-2016, 19:50

edoz wrote:

Bitmaps are in normal memory because MSX is the only machine that has a VDP.

...and because:
- bitmaps can use any amount of memory within the supported 1024KB ram
- there is not much video ram left, if using SymbOS in screen 7, beside the ram used for the display a huge amount of ram is used for the cached system font (to be able to plot it very fast with all 16 colour combinations)

By flyguille

Prophet (3029)

flyguille's picture

01-01-2016, 20:22

within the supported 1024KB ram. Why only 1024KB?

By edoz

Prophet (2179)

edoz's picture

01-01-2016, 20:28

flyguille wrote:

within the supported 1024KB ram. Why only 1024KB?

Because the CPC does not support more that that Wink

Don't forget the MSX is the beast amongst the 8 bit home computers Wink It can have a lot of memory and it does have a VDP.. which is less normal for 8 bit home computers Big smile For the information it is hard to get the 1024 full in SymbOS Big smile

By edoz

Prophet (2179)

edoz's picture

01-01-2016, 20:30

Manuel wrote:

My guess is that it's due to the aforementioned VDP I/O delay on the turboR. But it's a guess... I don't know the details at all and thus I might be completely wrong.

interesting.. do you want to say the the VDP cannot handle the fast r800?

By Manuel

Ascended (15825)

Manuel's picture

01-01-2016, 21:02

Quoting Wouter from http://www.msx.org/forum/development/msx-development/3d-rayc...

Quote:

Actually it's not about having always more than 52 cycles between VDP IO operations. It's about having to do less work 'outside' VDP operations. If the S1990 detects an IO to the VDP that is less than 62 cycles after a previous IO, it will stall the R800. The IO itself takes 10 cycles, so that means
there is room for 52 other cycles to do useful work. So what I tried to do is move as much work from before the 1st or after the 2nd IO instruction to between the 2 IO instructions.

The R800 is slowed down if it tries to access the VDP too quickly. So to optimize stuff, you'd better prevent that :)

By edoz

Prophet (2179)

edoz's picture

01-01-2016, 21:29

Wow! thanks for sharing! This is very interesting ... so when it stalls the R800 the CPU time is lost?
Somehow it is cool to see this back in the score Wink

By Prodatron

Paragon (1788)

Prodatron's picture

01-01-2016, 21:42

@Manual/Wouter: Very interesting! I will have a look at the VDP routines if it's possible to optimize it.

flyguille wrote:

within the supported 1024KB ram. Why only 1024KB?

Due to it's CPC origin, which is limited to 576KB, I decided to limit the address space to 20bit (16bit+4bit) = 1MB. Though most functions would even allow 24bit (16+8) = 16MB - so it could be possible to expand it, but at the moment it won't make much sense, as the number of applications (24) and processes (32+32) are limited as well. TBH when I started this stuff on the Z80, I didn't imagine that there would be an issue with these "limitations".

By flyguille

Prophet (3029)

flyguille's picture

01-01-2016, 22:12

Prodatron wrote:

@Manual/Wouter: Very interesting! I will have a look at the VDP routines if it's possible to optimize it.

flyguille wrote:

within the supported 1024KB ram. Why only 1024KB?

Due to it's CPC origin, which is limited to 576KB, I decided to limit the address space to 20bit (16bit+4bit) = 1MB. Though most functions would even allow 24bit (16+8) = 16MB - so it could be possible to expand it, but at the moment it won't make much sense, as the number of applications (24) and processes (32+32) are limited as well. TBH when I started this stuff on the Z80, I didn't imagine that there would be an issue with these "limitations".

Yeah, it is prefferable, unless you already give other meaning to msbs don't limit it to just 1MB, my humble MSX2 has internally 2MB already.

By -Neo-

Champion (380)

-Neo-'s picture

07-01-2016, 19:12

@Prodatron
I understood you have GR8NET running on SymbOS. Is that version downloadable somewhere?

By edoz

Prophet (2179)

edoz's picture

07-01-2016, 20:01

Hi neo, what is your msx configuration? Prodatron is very busy creating a new release package for fair in Nijmegen. Kind of last pre release package. There are still some bugs but i maybe I can send you a copy of my current installation so you can test it. But therefore I need your config. Which msx , which storage device in which slot.

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