Did SofRun 0.8 just erased my Omega MSX ROM ?

Hero (575)

14-05-2022, 10:56

So I built an Omega MSX that has a MX29F040 ROM chip. The first Sofarun test running from a Mapper Megaram and I choose XEVIOUS.ROM.

SofRun then decides the device to write as MegaFlashROM SCC and then hangs and my Omega MSX does not boot anymore.

I pulled the ROM and it was blank....amazing!

بواسطة gdx

Enlighted (6438)

14-05-2022, 11:42

I'm surprised that the designers of the Omega MSX did not anticipate it. Sunrise did it for their interfaces. It's pretty simple to do, just swap bits of data. That makes 64 possibilities.

I think you can put a pull-up resistor with a switch on the /WE pin of the flash Rom to make a write disable/enable.

بواسطة Manuel

Ascended (19683)

14-05-2022, 14:26

So that is not an actual ROM chip, but a programmable flash chip?

بواسطة S0urceror

Master (220)

14-05-2022, 21:02

Wanted to add a similar flash chip in my NMS8250 to be able to easily flash a new BIOS like with the right RAM counter, etc. But if Sofarun overwrites it then this is not a good solution. Maybe we can get Sofarun recognize this correctly.

بواسطة gdx

Enlighted (6438)

15-05-2022, 02:53

S0urceror wrote:

Wanted to add a similar flash chip in my NMS8250 to be able to easily flash a new BIOS like with the right RAM counter, etc.

It is quite complicated to rewrite the flash Rom that contents the system ROMs because the disks do not work without BIOS or Disk-ROM. And what will you do when the content of the flash gets corrupted because the data retention time in flash Rom doesn't exceed ten years?

You will have to remove the flash Rom each time to rewrite it with a PC. It's inconvenient.

بواسطة retrocanada76

Hero (575)

15-05-2022, 06:50

Well you could read everything to the memory mapper and write from there provided you have enough MM. But you can assume you write 256KB twice for example.

بواسطة gdx

Enlighted (6438)

15-05-2022, 09:39

Used Flash Rom in the Omega MSX is an SST39SF040. I just saw the datasheet, data retention is rated at greater than 100 years. So no problem for that. Rewrite endurance is 10 times less than AMD flash Roms but it's more than enough for this use. No need to rewrite the BIOS very often. However, it is better to add a switch or a jumper to write protect and do it in such a way that the Flash Rom remains easily removable in order to be able to rewrite the system ROMs in the problem event. The location seems to have been planned.

https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=...

بواسطة retrocanada76

Hero (575)

16-05-2022, 10:01

it happened again... :/ my other SD card didn't have the megaram as preferred device.... it is funny that OPFX.COM works fine with my MegaFlashROM SCC+ in my omega the problem seems the old non plus version, the SCC and probably the OPF.COM but I don't have these to try

بواسطة gdx

Enlighted (6438)

16-05-2022, 10:31

Put a jumper as indicated above to avoid the writings to the flash Rom. I think 2.54mm is the right pitch.

بواسطة retrocanada76

Hero (575)

16-05-2022, 18:49

but where ? The only jumper for the flashrom is for the pin 18 it will select the lower / higher 256k bank.

بواسطة Louthrax

Prophet (2496)

16-05-2022, 20:26

Hi Retrocanada,

When in "Auto" mode, SofaROM selects the "best" device for flashing. It has several criterias for that: patching required or not, is it a Flash device that might suffer from multiple rewrites, maybe other things that I do not remember... You can always change the default device from "Auto" to whatever device you want, and even select the slot to use.

To give more details: if a Flash device is available, SofaROM checks if it is not already used as a DiskROM. If yes, it's discarded. I could add other restrictions if they make sense - if the Flash device is in main slot 0 for example ? Not sure about what's happening with the Omega MSX...

EDIT: Also, the jumper solution to protect devices you want to protect seems a good idea !