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Different ROMs for Lambda 8300

Posted: Tue Apr 03, 2018 10:00 am
by mrtinb
There seems to be quite a few ROMs that works with the Lambda 8300:
  • Lambda 8300
  • Marathon 32 (includes color keywords)
  • ZX81 ROM
  • Modified ZX81 for Lambda 8300
Can we get an overview on what features are in which ROMs?

What does the "ZX81 modified ROM for Lambda" give me, that the "ZX81 ROM" does not?

Lambda 8300 with ZX81 ROM (I think)

Posted: Tue Apr 03, 2018 9:29 pm
by mrtinb
Lambda 8300 with ZX81 ROM (I think).

I inserted a ZX81 ROM, but that does not work. Maybe the Lambda insists on a modified ZX81 ROM.

https://youtu.be/Eyz3EM5ADJY

Re: Different ROMs for Lambda 8300

Posted: Tue Apr 03, 2018 9:53 pm
by gammaray
Your Lambda is probably PAL?... and your ZX81 does PAL or NTSC based on... what is it PIN22 of the ULA? Using R30 pullup resistor?

Lambda probably doesn't have that type of ULA...hmmm. ROM code changes on that maybe?

https://k1.spdns.de/Vintage/Sinclair/80 ... Kong/ROMs/

What about comparing schematic of US Futura 8300 and Lambda 8300?

https://en.wikipedia.org/wiki/Lambda_8300

Re: Different ROMs for Lambda 8300

Posted: Tue Apr 03, 2018 11:27 pm
by mrtinb
Ah...

Lambda has different port for detecting PAL. That’s why I need a modified ZX81 ROM.


PC8300 I/O PORTS

I/O:NNFEh.R ;read keyboard (A8..A15=row) (and CAS.IN) (and JOYSTICK)
;(but no PAL/NTSC bit here, unlike ZX81)
I/O:FF7Eh.R ;read PAL/NTSC flag (A7=row) (via diode from A7 to KEYB.0)

Re: Different ROMs for Lambda 8300

Posted: Tue Apr 03, 2018 11:46 pm
by 1024MAK
The other difference I believe, is the character dot matrix data is in ROM on the ZX81, but in the "ULA" on the Lambda...

Mark

Re: Different ROMs for Lambda 8300

Posted: Tue Apr 03, 2018 11:58 pm
by Andy Rea
1024MAK wrote:
Tue Apr 03, 2018 11:46 pm
The other difference I believe, is the character dot matrix data is in ROM on the ZX81, but in the "ULA" on the Lambda...

Mark
With this lambda talk lately i was looking at the schematics wondering how on earth the display was generated... That explains it... Cheers

Re: Different ROMs for Lambda 8300

Posted: Wed Apr 04, 2018 7:16 am
by mrtinb
So the half shade chars are replaced with diagonal triangles and a gaming “racing cars” char.

The £ char is replaced by a gaming “spider”.

The weird thing is that “:” and “?” chars are replaced with gaming chars as well. Here we have gaming “summer bird” and gaming “ghost”.

Re: Different ROMs for Lambda 8300

Posted: Wed Apr 04, 2018 8:23 am
by mrtinb
mrtinb wrote:
Tue Apr 03, 2018 11:27 pm
Lambda has different port for detecting PAL. That’s why I need a modified ZX81 ROM.
Unfortunately http://problemkaputt.de/zxdocs.htm#lambda830 states that the modified ZX81 ROM for Lambda is hard coded to 60 Hz. That will not work with my European tv. :cry:

Re: Different ROMs for Lambda 8300

Posted: Wed Apr 04, 2018 3:10 pm
by XavSnap
Lambda8300.jpg
Lambda8300.jpg (39.19 KiB) Viewed 2508 times

Re: Different ROMs for Lambda 8300

Posted: Wed Apr 04, 2018 4:15 pm
by gammaray
Sounds like someone with decent assembler skills would need to go after this one.

Addendum: The Futura 8300 was the unit for the U.S. so maybe it is built into the original ROM code/ULA to switch video?