Diskrom mirror differences between openMSX en BlueMSX

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Por Manuel

Ascended (18783)

Imagen del Manuel

28-01-2007, 01:14

Did you see if the ROM is mirrored in openMSX? It seems ony those FDC registers are, according to Wouter.

Por Manuel

Ascended (18783)

Imagen del Manuel

28-01-2007, 13:20

Does someone have a real unmodified Philips VG 8230 and/or Philips VG 8235? I'd like to get a sha1sum of their diskROMs....

The one we used so far are from a 32kB ROM image, and I don't think that can be correct. I'd gladly have this verified. Especially the 8230 is important, it cannot be found on the net.

The 8235 ROM from MESS and blueMSX are almost identical, except for a few bytes at the end, which are probably the FDC registers, so I think that is a reliable dump. But having that verified would be quite nice Smile

By the way, it seems the 8230 ROM (from the image I have) is quite different from the 8235 one. If you format on a 8230, it prints this:

Drive name? (A,B) a

Single Sided ...
( Use another drive for Double Side )

Strike a key when ready 

The 8235 doesn't print that remark about single sided at all.
If you don't put a disk in the drive, it then says:

Write protected

The 8235 dump I have says "Not ready".
Also, this 8230 starts up a lot slower than the 8235...

Anyway, if you have a 8230 and/or 8235, please see if you can confirm this and most importantly, get me a sha1sum of the diskROM dump.

Por zeilemaker54

Champion (341)

Imagen del zeilemaker54

29-01-2007, 16:17

About the VG8230: May be it has something to do with the fact that the FDC controller has the READY line connected to +5V and that "Ready" detection is done with the INDEX line in combination with a software loop. It could also be a buggy version of the diskdriver.
@manuel: if you have a romdump of a VG8230, i would be interested too!
@kwik: thanx for your comment on msxsyssrc Smile

Por msxrestarter

Master (224)

Imagen del msxrestarter

29-01-2007, 18:55

I have a 8230 (and also some 8235's, but that not so special I think) and would like to help but I don't know how to make a romdump of the diskrom(s).
If you tell me how, I'll try to get them for you Wink

Por Kwik

Expert (127)

Imagen del Kwik

29-01-2007, 20:39

@zeilemaker54: I think there might be an error in the DPB (for 0xFB) of the 8250, FS-A1GT, HB-F700-p-alt and HBD-F1 (haven't checked them all by the way).

As far as i can tell, FIRREC (the first sector where the data area begins) should be 12 and not 10.

0 bootsector
1 fat
2 fat
3 fat (second)
4 fat (second)
5 directory (112 entries / 16 = 7 sectors)
12 data area

Correct? Is this an error in the sources, of perhaps a bug in the roms?

Por flyguille

Prophet (3028)

Imagen del flyguille

29-01-2007, 21:54

I remember this, when I dissasembled one diskrom

IIRC at bootsector is 8 or 10, but as the two first element at fat is the ID media, so if at boot just set 12 that means that the two first clusters are not usable.

so, at boot sector the location of the first clustor is set at the end of the root directory, so the two first clusters (unusable) fall at the end of the root directoty and the first usable FAT element, fall at sector 12 allowing the use of all the disk space.

Por flyguille

Prophet (3028)

Imagen del flyguille

29-01-2007, 22:19

Anyway the diskrom doesn't read the boot sector looking for the format and the location of the data...

It uses internal format tables in ROM....

To identify the disk format, it only reads the sector 1, looking for the ID media....

But it reads the boot sector looking for the boot-code when you turn on the msx. Then it is unused (atleast in basic)

Por Manuel

Ascended (18783)

Imagen del Manuel

29-01-2007, 22:26

msxrestarter: ah, that would be great! The best thing to do that would really help is this:
- get saverom.com from http://bifi.msxnet.org/msxnet/utils/saverom.html
- put it with MSX-DOS on a single sided floppy (duh! :)
- do this:

saverom 8230-30.bin
Primary slot: 3
Secundary slot: 0
MegaROM? n
Start address: 0
End address: FFFF

and then the same for slot 3-3:

saverom 8230-33.bin
Primary slot: 3
Secundary slot: 3
MegaROM? n
Start address: 0
End address: FFFF

and then also for the 8235.

This would give us all we need to know to perfect the emulation of those machines.

We did the same on the 8245, 8250 and 8280 and there were interesting results!

On a 8245, the subROM is only visible in page 0 (slot 3-0). On the 50 and 80, the subROM is visible in all 4 pages in slot 3-0! (Now also in openMSX.)
On a 8245, the diskROM is visible in page 1 in slot 3-3 and the FDC registers are also mirrored on page 2 (as Kwik discovered, this is in (almost?) all openMSX machines with FDC). But on the 50 and 80, the FDC registers are visible in all pages!

So, I'm really curious how this is on the 30 and 35 (and also about the subROM on the 8220!). So, if you can help us here, it would really be great :)

Por Kwik

Expert (127)

Imagen del Kwik

29-01-2007, 22:30

What i meant was that FIRREC at sector 10 cannot be right, because it would overlap part of the directory entries.

Por flyguille

Prophet (3028)

Imagen del flyguille

29-01-2007, 22:33

nono as I explained before.

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