ZX81X2.ROM - and the big bang

Anything Sinclair ZX Basic related; history, development, tips - differences between BASIC on the ZX80 and ZX81
Moggy
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Re: ZX81X2.ROM - and the big bang

Post by Moggy »

Just burned this to my last EPROM and can agree, much faster SQR routines,some other maths function feel faster and the all BASIC game "Alien Mind" by Andre Baune is now nearly as smooth and fast as M/C.

The PAUSE routine without the flicker is a nice addition too.

Still some more playing around to do but I will say this a most welcome and appreciated new ROM.



Well done and many thanks Zsolt. :mrgreen:
Joachim
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Re: ZX81X2.ROM - and the big bang

Post by Joachim »

Thanks a lot, Zsolt! It's coming to the right time!
Joachim
Trevor_B
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Re: ZX81X2.ROM - and the big bang

Post by Trevor_B »

I'm looking to get an eprom programmed with ZX81X2 - is there a particular type of eprom I should be looking at? I used a 27C64 for my Minstrel 3 - would the same chip work on an original ZX81 series 1 board?
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1024MAK
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Re: ZX81X2.ROM - and the big bang

Post by 1024MAK »

Yes, a 2764, 27C64, 27128 or 27C128 type should be okay. But some wiring changes are needed because the EPROM pin out is not exactly the same as the ROM / socket pin out. There are no easy to get EPROM chips that have the same pin out as the socket.

There is however a module that is pin compatible here.

Mark
Moggy
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Re: ZX81X2.ROM - and the big bang

Post by Moggy »

2764 only two wires to alter dead easy no adapter needed, this is all I use with no problems and use a ZX spectrum to program them.

If you already have 2c764's then it's a no brainer rather than shelling out £20 for a pre-programmed modern version in my opinion.
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Trevor_B
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Re: ZX81X2.ROM - and the big bang

Post by Trevor_B »

I've sent RWAP a message about getting the compatible chip programmed, but looking at your picture - that's VSS (pin 14) to CE (pin 20 - pin 20 not socketed) and A11 (pin 23 - not socketed) going to somewhere - unfortunately I can't see where on the pic. Can you fill in the gap please?

I'm happy enough to make the change in either format tbh - RWAP is probably easiest but I'm also not averse to bending pins and soldering jump wires now!

Trevor
Moggy
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Re: ZX81X2.ROM - and the big bang

Post by Moggy »

The wire from pin 23 now occupies the hole vacated by pin 20.

A much more elaborate wiring manner was used previously until someone jointed out that the motherboard already provided those connections albeit unused, almost as if Sinclair anticipated some kind of future EPROM use. Fortunately we now have this much simpler method.
Last edited by Moggy on Sun Jan 31, 2021 5:52 pm, edited 1 time in total.
Trevor_B
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Re: ZX81X2.ROM - and the big bang

Post by Trevor_B »

Ok - looks easy enough. I'm going to give it a go.. what could possibly go wrong <<insert horror story here>>.

Trevor
Moggy
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Re: ZX81X2.ROM - and the big bang

Post by Moggy »

Trevor_B wrote: Sun Jan 31, 2021 5:49 pm Ok - looks easy enough. I'm going to give it a go.. what could possibly go wrong <<insert horror story here>>.

Trevor
At least twenty done by myself (Forth ,AZMIC, big bang etc) no problems whatsoever and I'm the forum Klutz! :lol:

2 wires to solder easy peasy.
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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: ZX81X2.ROM - and the big bang

Post by 1024MAK »

Slips in quietly...

...... look here ......

I’ve got a diagram somewhere, but that’s buried in a pile of notes....

Exits stage right...

Mark
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