Cannot use SD-512 with Tecnobytes Double RAM

By Tarnyko

Rookie (31)

Аватар пользователя Tarnyko

03-09-2019, 23:02

Hi folks, I recently acquired a MegaRAM cartridge to be able to run huge games from disk, but face issues using it with my initial IDE/SD device cartridge. I wondered if you could help.

I own a Philips NMS 8220, which is a 64 Kb MSX2 -already using a 512 Kb Memory Mapper cartridge to boot Nextor and run SofaRUN on a SD card (which happens to be a feature of the same cartridge).
The cartridge is a 8bits4ever SD-512.

So with this SD-512 Cartridge on slot 1, I have ~512 Kb RAM, Nextor, and a partition "A:".
I ran MEM.COM so you can see the initial memory:

I ran FDISK so you can see the initial partition, on slot 2-1:

If I add the Tecnobytes Double RAM cartridge on slot 2, in "MegaRAM" mode (see here), it still tries to boot Nextor, but doesn't seem to find the partition anymore, hence falls back to BASIC.
CALL SYSTEM doesn't work (DOS in on the partition), FILES "A:" and DSKF(1) show nothing:

If I run _FDISK, I see the unformatted 8 Mb cartridge partition:

It seems to occupy the same slot than my usual partition : 2-1.
So I guess it is why my initial partition (SD-512) isn't found: they share the same slot.

How can I keep access to my initial partition, and have the Double RAM at the same time ?

Maybe I need to modify my Nextor kernel (NEXTOR.SYS) on the SD card, so it detects the Double RAM differently ?

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By djh1697

Paragon (1410)

Аватар пользователя djh1697

04-09-2019, 00:09

The correct syntax is
Print dskf(0)

Have you tried swapping the cartridges around?

If you are using sofarun there is no need to use your RAM expansion as a MegaRam? Since SofaRun will use a conventional mapper?

By Tarnyko

Rookie (31)

Аватар пользователя Tarnyko

04-09-2019, 08:10

Hi @djh1697, and thanks for the help,

- dskf(): you're totally right. I fixed it later. The point was, showing the command doesn't work at all :( .

- Swapping: yes I tried it; the result is exactly the same (same Nextor kernel version, doesn't boot to DOS, only boots to BASIC, doesn't see the SD partition).

My objective, by using Tecnobytes Double RAM, was to be able to run "big" (>2MB) games such as Pointless Fighting with SofaRun. My feeling was the MSX has enough RAM (512 K) to run the game, but SofaRun needs a MegaRAM to temporarily "unpack" the 2 Mb file (see this page for the initial analysis). Don't you think it's correct ?

(PS : the issue arises anyway, whether I define the Double RAM as a MegaRAM, or a Memory Mapper, with the physical switch)

By Pentarou

Master (226)

Аватар пользователя Pentarou

04-09-2019, 08:57

What is the real size of your SD card?
In the 2nd picture from the top it looks like a 2GB card, but in the last picture it looks like an 8GB card???

If you disable the RAM of the SD-512 (switch on the left), can you boot into dos and run a test on the Double-RAM memory?

By Tarnyko

Rookie (31)

Аватар пользователя Tarnyko

04-09-2019, 09:18

Real size is 2 Gb.
8 Gb is what gets displayed by _FDISK when I connect the Double RAM in MegaRAM mode.
I interpreted this as Nextor detecting the MegaRAM flash (4Mb), but reporting it incorrectly. But maybe it's just a bug ?

I guess that to try 2), as DOS resides on the SD card currently, I'd need a DOS cartridge or a floppy disk drive with a DOS-formatted disk, don't I ?

By Pentarou

Master (226)

Аватар пользователя Pentarou

04-09-2019, 14:17

Maybe there's something wrong with your SD card if the SD-512 can't detect the size correctly.
I also find it strange that it can't identify the maker id

Quote:

00000 (1)

Can you test another SD card?

Tarnyko wrote:

I interpreted this as Nextor detecting the MegaRAM flash (4Mb)

No, that can't be. It's definitely a bug or a problem with your SD card. And the only flash in those 2 carts is the SD-512's BIOS (128 Kb).

Tarnyko wrote:

I guess ... I'd need a DOS cartridge or a floppy disk

No, you can disable the RAM of the SD-512 and still use the SD card reader part. That's what the switch on the left does.
But since your 8220 has only 64Kb you have to use the Double RAM in Mapper mode.

By Tarnyko

Rookie (31)

Аватар пользователя Tarnyko

04-09-2019, 22:52

This is good advice !

Quote:

Can you test another SD card?

Will do it.

Quote:

No, you can disable the RAM of the SD-512 and still use the SD card reader part. That's what the switch on the left does.

So I'm reversing the situation. Good idea.

It may take some time, up to a week (I'm in another country). Will keep you updated.