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CAC-3... another Lambda 8300 variant ?

Posted: Tue May 09, 2017 3:44 pm
by davidebarlotti
I got here in China a ZX81 clone that has a case similar at Lambda 8300 and should have the same ULA.
Interesting the presence on board of 16Kb and a additional ROM with a monitor.
I change the original ROM 2364 with a EPROM 27c64 (BTW interesting that are present two welding pad/switch to change two pin signals on the socket)
using the Lambda8300 rom with ZX81 compatible mode and using the TZXduino I'm able to load and run 16kb program :)
Here the video with some screenshoots and computer photos.

I'm asking firstly if some one has this clone or have more information.
Second if and where I can download software specific for the Lambda 8300.
Googling I found this site where seems the author has dumped some games/programs without share any link.
Anyone has something to share?

Re: CAC-3... another Lambda 8300 variant ?

Posted: Sat May 13, 2017 11:05 am
by mrtinb
Due to a week with the flu there's been a delay in my response. ... ng%20Kong/ ... am/lambda/

We are back in the age where few programs were sold, and most programs were made by yourself. So now you've got the documentation, and can create your own master piece.

My Lambda 8300 has a dead ULA at the moment, but hope to be able to create a modified ZX81-ULA someday for it.

There are some german articles about the Lambda 8300 in these magazines:

Re: CAC-3... another Lambda 8300 variant ?

Posted: Mon May 15, 2017 9:34 am
by davidebarlotti
thanks Martin for your sharing.

At the end seems the ZX80/81 community don't have any dump specific for the lambda :(
So a way is spend some time to typing some programs present on ZX-team magazine
and found a way to save.

Interesting try to use the original ULA or a "original" clone not only to fix your unit
but also for use the "standard" character set that in Lambda 8300 that are stored on the ULA C4005
and seems not possible to change just changing the ROM.

But for the Lambda 8300 ULA C4005 noted the pinout different and some address line aren't connected
On C4005 ULA (in according a scheme from Power3000) are used:
A0 A1 A3 A10 A14 A15 (no A2, A4, A5, A6, A7, A8)

On Zx81 are used:
A0 A1 A2 A3 A4 A5 A6 A7 A8 A14 A15

Other differences:
HALT and C signals are connect directly to CPU on L.8300
on ZX81 are present additional components.
pin 39 is connect to Data bus via a 74ls05,
I don't know the reason and seems isn't present a equivalent pin in the ZX81 ULA.

So at the end I believe will be no obvious replace C4005ULA

Meanwhile a got another "Chinese clone" called NF300.
Still need to fix (seems have a short circuit to ground on 12V input)
Is based with the same C4005 ULA (remarked as C4335) and has the ROM
with different boot screen NF-BASIC 1 but with the memory detection has the CAC-3.
Curious the approach for the user port: they have close the slot but they have keep
the pads on the PCB without bring any signals !?!...

Re: CAC-3... another Lambda 8300 variant ?

Posted: Mon May 15, 2017 9:44 am
by mrtinb
Thank you for your observations. I have not digged into this yet.