SSupport All BIOSes of Tandy 1000 (8088) Variations

[wark91]

Hi,

The bioses of Tandy 1000 (8088) variations highlighted show this error below :
1000 128KB-640KB RAM 4.77 MHz v01.00.00, v01.01.00
1000A/1000HD 128KB-640KB RAM 4.77 MHz v01.01.00
1000SX/1000AX 384KB-640KB RAM 7.16/4.77 MHz v01.02.00
1000EX 256KB-640KB RAM 7.16/4.77 MHz v01.02.00
1000HX 256KB-640KB RAM 7.16/4.77 MHz v02.00.00

20221115_160225-screen.png (18.84 KiB) Viewed 1584 times

Thanks for your time on this core !

[spark2k06]

Hi,

The bioses of Tandy 1000 (8088) variations highlighted show this error below :
1000 128KB-640KB RAM 4.77 MHz v01.00.00, v01.01.00
1000A/1000HD 128KB-640KB RAM 4.77 MHz v01.01.00
1000SX/1000AX 384KB-640KB RAM 7.16/4.77 MHz v01.02.00
1000EX 256KB-640KB RAM 7.16/4.77 MHz v01.02.00
1000HX 256KB-640KB RAM 7.16/4.77 MHz v02.00.00

20221115_160225-screen.png

Thanks for your time on this core !

I know, the only one that works is Tandy 1000. You might solve that problem, and others will come up...maybe.

[Flandango]

That's an easy fix...at least for the SX bios. Some of the other bioses have other requirements that may not be implemented yet, such as larger BIOS rom space, NVRAM...etc.
I am out of town at the moment so I don't have access to my test environment but I had it working.
If you are interested in trying to compile it yourself to test in the mean time here is what you need to modify:
in PCXT.sv of main branch at line 978, you'll see:

Code: Select all

		.port_b_out                         (port_b_out),
		.port_c_in                          (port_c_in),

add this line:

Code: Select all

		.port_b_in                         (port_b_out),

Once you get past that keyboard error, it will hang waiting on the co-processor test,
so you will need to also change this line in rtl/8088/i8088.v

Code: Select all

    .TEST_N_INT             (1'b1),

to

Code: Select all

    .TEST_N_INT             (1'b0),

Some info on the 2nd change...
The bios tests to see if there is an 8087 math co-processor installed and, if my memory is correct, it uses the FWAIT instruction to wait for a response. If the system includes one, it will lower the TEST pin on the processor. If the system didn't have one, the TEST pin was brought down via jumper.
As currently coded, the TEST pin (TEST_N_INT) is left high and the bios just waits infinitely.
If in the future, the co-processor is implemented, then it will be tied to this TEST pin. Till then a better solution is probably make it a OSD toggle switch to keep it low. I have not come across any other instruction or use case for the TEST pin so it may not hurt to keep it low for now.

[spark2k06]

As currently coded, the TEST pin (TEST_N_INT) is left high and the bios just waits infinitely.
If in the future, the co-processor is implemented, then it will be tied to this TEST pin. Till then a better solution is probably make it a OSD toggle switch to keep it low. I have not come across any other instruction or use case for the TEST pin so it may not hurt to keep it low for now.

Thank you for the information. Yes, I had already identified the TEST_N_INT thing from another debug I did, I was going to make precisely that change, set it to 0... about the PCXT.sv file, I'll change it and try it, I'll do it tomorrow and I'll tell you something.

[spark2k06]

Changes made:

https://github.com/MiSTer-devel/PCXT_Mi ... 8c1bff4c40

Now it overcomes the keyboard error message, but it stops somewhere else:

20221116_055149-screen.png (324.23 KiB) Viewed 1361 times

It does not seem to initialise the video.

[wark91]

Thanks for the change. I compiled it.

Tandy 1000 v1.03 bios works. We have 630K for programs

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Tandy 1000 HX v2.0 stuck at this point

20221116_083559-screen.png (15.69 KiB) Viewed 1321 times

Thanks

[spark2k06]

Thanks for the change. I compiled it.

Tandy 1000 v1.03 bios works. We have 630K for programs

Yes, but you'll find that you won't be able to play games in Tandy graphics mode... and PC-Speaker doesn't work either, anyway, we are already seeing that each BIOS has its own particularities, adapting to all of them doesn't seem to be easy.

[wark91]

I see. I didn't try game for my first test.

[spark2k06]

We were lucky that the first Tandy 1000 wasn't too fussy, with a little tweaking of the keyboard part it was enough. Another BIOS for example that doesn't work is the IBM5150, it seems that because of some video issue, we have to switch to IBM5160.