Basic eprom for nms8220

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Door makinavaja

Master (219)

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30-12-2020, 10:51

Hi.
This week one friend ask me to fix his nms8220, purchased as a non working computer. Once I opened it, a little mess was discovered: A previos owner try to remove the basic eprom and, well, nothing good.
I managed to clean up all the holes, all tracks seems to survive and I have the service manual downloaded to be sure of that.
Anyway, looking for a spare eprom to prepare, I see that the original chip is an m531000-52 from kyocera, a 128KB rom, while the basic rom I can download here ( http://www.msxarchive.nl/pub/msx/emulator/system_roms/Europe... ) is only 32KB.
Wich kind of eprom should I use? should I concatenate the rom 4 times until I have a 128KB rom?

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Van Manuel

Ascended (18068)

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30-12-2020, 11:57

OmegaMSX found out that the 128KB ROM contains even an disk ROM Smile Only 48kB of it is actually used. There is a full dump of it available, it has sha1sum e761e7081c613ad4893a664334ce105841d0e80e
The BIOS/BASIC part starts at offset 64kB. The subROM is behind that.

Van makinavaja

Master (219)

afbeelding van makinavaja

30-12-2020, 13:24

and, where can I find that dump?

Van mars2000you

Enlighted (5954)

afbeelding van mars2000you

30-12-2020, 13:31

Search for Philips_NMS8220_System.rom - it's one of the system eproms available on a well-known MSX site (impossible to give the link here, sorry).

Van roadfighter

Champion (421)

afbeelding van roadfighter

30-12-2020, 16:43

makinavaja wrote:

Hi. Wich kind of eprom should I use? should I concatenate the rom 4 times until I have a 128KB rom?

A 27512 would do the trick. You can find them on aliexpress a lot.
Best you buy a EEprom then you can experiment with it, or when you have a eprom eraser that won't be a problem but takes a bit longer Smile
And for the dump of the 8220 basic rom, you have posted the link yourself.

Van makinavaja

Master (219)

afbeelding van makinavaja

30-12-2020, 17:42

roadfighter wrote:
makinavaja wrote:

Hi. Wich kind of eprom should I use? should I concatenate the rom 4 times until I have a 128KB rom?

A 27512 would do the trick. You can find them on aliexpress a lot.
Best you buy a EEprom then you can experiment with it, or when you have a eprom eraser that won't be a problem but takes a bit longer Smile
And for the dump of the 8220 basic rom, you have posted the link yourself.

The link I posted doesn't have any 128KB rom. It has only the nms8220_basic-bios2.rom, and its only 32KB. It's ok this one?
And, if I burn it on a 27512 eprom (512KB) will it work withouth preparing anything? I remember that on amstrad cpc6128 I had to prepare the rom copying it several times on the same file if I wanted to use a bigger eprom.

Van Manuel

Ascended (18068)

afbeelding van Manuel

30-12-2020, 18:14

2 directories up and then a zip file contains it.

Van roadfighter

Champion (421)

afbeelding van roadfighter

30-12-2020, 22:22

The link I posted doesn't have any 128KB rom. It has only the nms8220_basic-bios2.rom, and its only 32KB. It's ok this one?
That's the one.
A eprom 27128 is 16 Kb.
the 27256 is 32 KB
and the 27512 is 64 kb.
But i have no idea how the rom is prepared, i think you can use a 27512 and burn the rom into the first 32kb block.
Never had to try it, that's why i suggested a EEprom and solder a Socket in the computer, then u have some room for experimenting without to much hassle.

Van makinavaja

Master (219)

afbeelding van makinavaja

02-01-2021, 13:23

Hi again
Finally I did a test but it has been unsuccessfull, I still get a black screen. No logo, no basic, nothing.
I used a 27512 eeprom, and burned on it a 64 KB rom with the file nms8220_basic-bios2.rom concatenated twice with a copy /b.
The problem with this is that I dont really know if this computer has another hardware problem or a problem with the bios. :-/

Van Manuel

Ascended (18068)

afbeelding van Manuel

02-01-2021, 14:21

Perhaps you missed my post in which I explained how the ROMs are organized inside the 128kB EPROM? Also, you seem to have missed the subROM?

Van sdsnatcher73

Prophet (2143)

afbeelding van sdsnatcher73

02-01-2021, 18:12

@Roadfighter: I sent the file to your e-mail (may end up in a spam folder so please check)

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