ZX81X2.ROM - and the big bang

[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.

[Joachim]

Thanks a lot, Zsolt! It's coming to the right time!
Joachim

[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?

[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]

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.

[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]

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

A much more elaborate wiring manner was used previously until someone pointed 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.

[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]

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!

2 wires to solder easy peasy.

[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