Nextor - openMSX

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By Piter Punk

Master (184)

Piter Punk's picture

31-03-2014, 23:32

konamiman wrote:

Ok. Could you please try the following:

Open the Nextor ROM file in a hex editor and change the 3rd and 4th byte of each 16K bank, from D6-47 to F6-40.

If that works then I have some hard work to do...

I don't know if this is good or bad news to Nextor development, but with this change now I can boot Nextor on OpenMSX.
Boot with an empty HD file. I am formatting it using _FDISK now.

By Marcelo_Zoffy

Supporter (15)

Marcelo_Zoffy's picture

01-04-2014, 00:24

konamiman wrote:

Ok. Could you please try the following:

Open the Nextor ROM file in a hex editor and change the 3rd and 4th byte of each 16K bank, from D6-47 to F6-40.

If that works then I have some hard work to do...

Worked here after changes. Thank you so much!

By konamiman

Paladin (922)

konamiman's picture

01-04-2014, 10:10

Long and boring explanation of what's going on in case someone is interested:

The original MSX-DOS 2 kernel works as I had explained in my previous message. The first 255 bytes of all 16K banks are identical, and the INIT vector (the 3rd and 4th bytes of these initial 255 bytes) points to a short piece of code that ensures that bank 0 is selected (by calling the bank switching code at 7FD0h), and then jumps to the real initialization code in that bank. So far so good, but...

This scheme works fine as long as you are using a ROM mapper that works with 16K banks. If you use a mapper with 8K banks (such as ASCII8, the mapper used by MegaFlashRom SD SCC+), you cannot do the same thing, since you are not guaranteed to have the bank switching code available at 7FD0h at boot time (if you don't have a 8K bank with an odd number switched on the upper half of page 1, you are out of luck).

So what did I do? Well, I tried to simply assume that bank 0 was being mapped at boot time, and sice this seemed to be always true for blueMSX and for the MegaFlashRom, then I assumed that it would always be true... which in the end turned out to be wrong.

Luckily, the old (correct) boot code was still present in the compiled ROM file, so it is enough to patch the INIT vector to point to it, and it works again... for mappers with 16K banks only.

In the end I think that I will assume that a 16K mapper is going to be used, and treat ASCII8 as a special case when generating the ROMs. Well, time for a version 2.0.1 I guess.

By Roland007

Rookie (24)

Roland007's picture

05-03-2018, 19:37

Yeah, old thread I know, but I just wanted to try. I got it working with the tip in this thread. Can anyone tell me how I can make it work with my current HD in openMSX. Next boots up and goes to basic. _FDISK sees my HD but but booting: no way Smile

By Manuel

Ascended (14242)

Manuel's picture

05-03-2018, 19:57

Did you copy the necessary Nextor files to the first partition? NEXTOR.SYS and COMMAND2.COM I guess.

By Roland007

Rookie (24)

Roland007's picture

05-03-2018, 20:08

yes.

By Manuel

Ascended (14242)

Manuel's picture

05-03-2018, 21:57

konamiman: what is currently the status of Nextor on Sunrise IDE?

Roland: what exactly did you do?

Documentation seems to be here: https://www.konamiman.com/msx/msx-e.html (search for Sunrise IDE).

By Vampier

Prophet (2144)

Vampier's picture

05-03-2018, 22:46

Roland007 - https://www.youtube.com/watch?v=3wIXWq05t8M

if you don't object against running an MFR SCC+ SD instead.

By Roland007

Rookie (24)

Roland007's picture

06-03-2018, 09:09

I changed the IDE romfile ide250.dat in xml to nextor. I copied nextor.sys to a:\ (A is a FAT12 partition, currently used by MSX-DOS2). Ofcourse I read the documentation. Manuals assume a clean HD (blueMSX). I can imagine the following things:
- somehow nextor can't decide what portion to boot and drops to Basic regardless of nextor.sys in A: (so nextor.dat) might help
- both msxdos2.sys and nextor.sys can't live in A:\ and nextor skips that partition.

As far as I read: nextor should work 100% in openMSX (konamiman's site).

Cheers.

By Manuel

Ascended (14242)

Manuel's picture

06-03-2018, 11:16

You also need command2.com....

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