50/60Hz switch for MSX-DOS that checks VDP version?

Page 6/7
1 | 2 | 3 | 4 | 5 | | 7

By NYYRIKKI

Enlighted (5874)

NYYRIKKI's picture

10-07-2021, 00:29

sdsnatcher73 wrote:

This also explains why it worked on NYYRIKKI’s CX-5MII and not my CX-11

No, it does not work that way... I did not test on any computer real or emulated. I know how the system works and that is why I can give this kind of advices. This might sound exteremy bold, but I know ie. Grauw can share my thoughts. Once you know the system well enough, you don't anymore need to test these kind of things. It is just elecronics and assembly working together as is.

By gdx

Enlighted (4694)

gdx's picture

10-07-2021, 01:21

NYYRIKKI wrote:

To me "reserved" means do not touch... That means you should not try to write it or expect to read any meaningful value...

Yes but these ones are values we need for programs so these ones should be initialised to avoid this kind of problem. Reserved BIOS entries are initialised to 0. Not do it also for system variables is a mistake (even if this is not useful in the majority of the time).

By NYYRIKKI

Enlighted (5874)

NYYRIKKI's picture

10-07-2021, 01:30

gdx wrote:

Yes but these ones are values we need for programs so these ones should be initialised...

Yes... Extremely easy to say now... but I don't think that Nishi or other people were even aware that "next version" is going to be made by Yamaha... and even if they did I doubt they would know how these memory addresses would be used on Yamaha design.

I think it is fair to say that some addresses may be used for future enhancements and not used now, but saying "now we need them and you should make them work on previous generations" is a bit... well... not fair.

By gdx

Enlighted (4694)

gdx's picture

10-07-2021, 01:46

Anyway, the only solution to fix this problem is to modify the Bios or to upgrade the MSX1s with V9938 to MSX2. We can't make a command 100% operational.

By NYYRIKKI

Enlighted (5874)

NYYRIKKI's picture

10-07-2021, 01:47

gdx wrote:

Reserved BIOS entries are initialised to 0

And BTW not a good idea... initializing with #C9 would have been much better. While looking from my point, not well thought call that eventually ended up to middle of keyboard handling routine was a real killer ie. on Nemesis III

By NYYRIKKI

Enlighted (5874)

NYYRIKKI's picture

10-07-2021, 02:00

gdx wrote:

Anyway, the only solution to fix this problem is to modify the Bios or to upgrade the MSX1s with V9938 to MSX2. We can't make a command 100% operational.

No, I would say that is wrong approach... I would say it would be better to make V9938 registers readable by CPU from the start. I have actually suggested this many times, but unfortunately HW engineers have not been interested... and I feel it is a bit shame. This would make it possible to do all kind of nice tricks ie. save states and such. Today that would not take much effort and as you know, we can't change the past.

By gdx

Enlighted (4694)

gdx's picture

10-07-2021, 02:33

We can't change the past but we can change the BIOS. Wink
And to upgrade an MSX1 with V9938 to MSX2, we need only 2 VRAM chips and an MSX2 BIOS with its sub-ROM.
This is cheap and not complicated. No interest to let this machine in MSX1.

By NYYRIKKI

Enlighted (5874)

NYYRIKKI's picture

10-07-2021, 03:03

You talk about 4 chips and few passive components... Yes, been there, done that. Imagine a chip/cartridge that just listens I/O and captures the few going to VDP... Naturally few exceptions like palette and auto increment registers should be considered, but generally just a very simple device sitting on a bus.

Ok, I'm once again 1000 miles from the subject, but it already got out of hand quite long ago. Smile
(sorry)

By Grauw

Ascended (10062)

Grauw's picture

10-07-2021, 10:22

gdx wrote:

We can't change the past but we can change the BIOS. Wink
And to upgrade an MSX1 with V9938 to MSX2, we need only 2 VRAM chips and an MSX2 BIOS with its sub-ROM.
This is cheap and not complicated. No interest to let this machine in MSX1.

But I don’t want to upgrade it Smile. I think it’s a cool quirky MSX1+ machine as it is, I don’t need another MSX2. And it’s good for software testing to leave it in its original state. Though I did swap the memory board for an 1M one, which is nice for VGMPlay.

By gdx

Enlighted (4694)

gdx's picture

10-07-2021, 10:50

Nyyrikki, do not think I'm trying to disparage your version. I'm only saying that there can't be an ideal solution except by upgrading to MSX2.

I stay always in the central issue from the start, And you do not have to apologize for not being agreed.

About the CX11 upgrade, You are right. It isn't as simple as for the CX5MII, YIS-503II and YIS-603.

The best would probably be to make a little board with the Z80, Sub-ROM and required RAM expansion (thus also an EPM) to replace the Z80. Alexey may have already done so.

https://www.msx.org/forum/msx-talk/hardware/yamaha-msx2-upgrade
https://tabajara-labs.blogspot.com/2018/07/a-transformacao-d...

In addition, internal RAM must be removed to improve the compatibility with software. In short, the upgrade is not so simple indeed.

Page 6/7
1 | 2 | 3 | 4 | 5 | | 7