marmotta wrote on 2022-04-21, 08:35:

Horun wrote on 2022-04-21, 00:18:

Can you post a picture of your board? Just because you have a 25Mhz Harris does not mean it is running at 25Mhz (I have a board with 20Mhz Harris in a 16Mhz board)...

This is my board, which card do you have?

I see no other reply that says this - the 32Hz crystal means your 286-25 is actually running at 16 MHz when you get it running again.

debs3759 wrote on 2022-04-25, 18:27:

marmotta wrote on 2022-04-21, 08:35:

Horun wrote on 2022-04-21, 00:18:

Can you post a picture of your board? Just because you have a 25Mhz Harris does not mean it is running at 25Mhz (I have a board with 20Mhz Harris in a 16Mhz board)...

This is my board, which card do you have?

I see no other reply that says this - the 32Hz crystal means your 286-25 is actually running at 16 MHz when you get it running again.

You missed the 50MHz oscillator that is present on the photo of the mainboard.

weedeewee wrote on 2022-04-25, 19:18:

debs3759 wrote on 2022-04-25, 18:27:

marmotta wrote on 2022-04-21, 08:35:

This is my board, which card do you have?

I see no other reply that says this - the 32Hz crystal means your 286-25 is actually running at 16 MHz when you get it running again.

You missed the 50MHz oscillator that is present on the photo of the mainboard.

Ah, yes. I was only looking for the metal can type of crystals 😀

vstrakh wrote on 2022-04-25, 06:29:

That is the way they've mapped the 8-bit rom onto 16-bit data bus. Some motherboards or ega cards would use two chips, this moth […]
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Horun wrote on 2022-04-22, 23:00:

Looks a bit odd. The AMI header even on 286 boards should always be readable and is but have to load in PCem or MAME to see if it really is OK.

That is the way they've mapped the 8-bit rom onto 16-bit data bus. Some motherboards or ega cards would use two chips, this motherboard uses single chip, and the most significant address line is used as a "byte select" input. So lower half of the chip stores even bytes, the upper half stores odd bytes.
The plain content as seen by cpu would look like this:
2cgm001_straight.zip

Thanks ! Yes I forgot that some early single ROM boards did that. The first 32k (0 to 7fff hex) would be odd, the second 32k (8000 to ffff) would be even bits.

386SX Citygate boards usually have an ALD 93c305 chipset (or something very similar). It's likely yours is the same or similar.

I have one of this board, the 50MHz oscillator is for the processor (25MHz) and the 32MHz is for the coprocessor in asyncronous mode (16MHz).
Since the 287xl is related at 12.5MHz, I 'll try to change the 32MHz oscillator for another but 25MHz.

I have one that is very similar too; soldered 20MHz Harris CPU.

I can't for the life of me get it to "take" a 287, and I haven't found any documentation for the onboard jumpers. As such, I have no idea if it's trying to run the 287 at 20 or 16 MHz (not a big difference).

I do notice however that the 287 tends to get quite hot quite soon, and it is not detected by the BIOS. Any DOS program that tries to talk 287-speak tends to hang; whether it's QRAM MFT or NDOS (the %_NDP variable).

Other than this, the board runs very stable even with 16MB RAM.

I have the same BIOS as everyone else, it seems.

Assuming your 287 is an intel 287 not XL version. They run very hot and don't like any overclock. So it not runs at 16 or 20MHz. Try swapping the crystal to a desired frequency times 2 (25MHz to a 12.5MHs clock and so on) .

Hello everybody!

Recently I got this board. It has the classical VARTA leakage but it looks well.

Here's my BIOS dump.

It has a different checksum than those who have been uploaded so far.

Perhaps it will help other users, let me know!

tauro wrote on 2023-09-15, 20:42:

Here's my BIOS dump.

Good afternoon!
Did you read it with a programmer or program?
I can’t try it now, but I’ve been looking for this firmware for a long time!
Thanks a lot!
If possible, send the firmware to info at theretroweb.com

marmotta wrote on 2022-04-22, 22:11:

Ok! Now I have the reader/programmer... this is the dump of original bios, seems ASCII read reveal a damaged contenent. If you want to take look 😉

Very similar to the bios from the TD60C... I can’t check it now.

"TD60C BIOS VERSION 2.42B" ="T6CBO ESO .2" - original
"T6CBO ESO .2" - version marmotta

led178 wrote on 2024-01-01, 16:16:

Good afternoon!
Did you read it with a programmer or program?

Privet!
I use a TL866 II-Plus.

led178 wrote on 2024-01-01, 16:16:

I can’t try it now, but I’ve been looking for this firmware for a long time!
Thanks a lot!

I'm really glad, I hope it helps! Post back your results.

led178 wrote on 2024-01-01, 16:16:

If possible, send the firmware to info at theretroweb.com

I've sent emails to that address in the past but I never got a single answer.