Sinclair ZX80 / ZX81 / Z88 Forums

Now I have my video output issues 99.99% solved.. I am thinking about Hi-RES.. not on software development but just trying out what is already done by others..
I've read several thread's and it seems that WR16 is the most used other than pseudo Hi Res.. my TS1000 intarnal ram is not working, Fortunately I have 3 16Kb packs 2 TS1016 (same as Sinclair's rampack), one not working presumably with some dead 4116 IC.. that I have to test and decide if I convert to 4164's and get rid of +12 and -5 lines... and a 3rd one I've made myself from a magazine back in the '90s that uses two 6264 (8K 8bit SRAM CMOS)..
I 've read somewhere that SRAM doesn't need to modify the rampak to implement WRX16.. did I get it Wright??
Else I see lot of bad characters (see attachment) at
Wilf Rigter's homepage.. does everybody see it like this? How can it be solved?
And last, Has any one made it ? Any tips and or pictures??
Thanks!!

In your web browser change text encoding to "ISO Latin 1" and reload the page. It should work fine.

BTW I've modified a few ram pack with Wilf's trick and they show WRX1K graphics correctly.

In order for any external RAM (SRAM or DRAM) to be hi-res capable, it has to respond to either the Z80 CPU performing a normal read (Z80 control line ‘/RD’ going low) or the Z80 refresh control line (‘/RFSH’) going low.

1N34A diodes are hard to get hold of these days, and if you do find some, they are rather expensive. So I suggest you use silicon Schottky signal diodes (e.g. BAT41, BAT42, BAT43, BAT46, or similar) instead of 1N34A diodes.

Of course rather than using a diode/resistor logic gate (which is what the circuit in the above post is), if you have a suitable spare logic chip, you can use that instead.

Mark

McKlaud wrote: ↑Thu Oct 31, 2019 7:05 am In your web browser change text encoding to "ISO Latin 1" and reload the page. It should work fine.

BTW I've modified a few ram pack with Wilf's trick and they show WRX1K graphics correctly.

Thank you!! I'll try to that
I'll see if Ican figure out how to do this inside the rampack case

1024MAK wrote: ↑Thu Oct 31, 2019 9:29 am In order for any external RAM (SRAM or DRAM) to be hi-res capable, it has to respond to either the Z80 CPU performing a normal read (Z80 control line ‘/RD’ going low) or the Z80 refresh control line (‘/RFSH’) going low.

1N34A diodes are hard to get hold of these days, and if you do find some, they are rather expensive. So I suggest you use silicon Schottky signal diodes (e.g. BAT41, BAT42, BAT43, BAT46, or similar) instead of 1N34A diodes.

Of course rather than using a diode/resistor logic gate (which is what the circuit in the above post is), if you have a suitable spare logic chip, you can use that instead.

Mark

Two diodes and one resistor doesn't seem to be difficult to fit . I have no clue about what logical gate is made here.. nor what IC will do the trick usually they are not expensive and easier to get than schottky diodes..

https://github.com/z88dk/z88dk/wiki/Pla ... ware-hints

Below the description of the two germanium diodes is a description of doing the same hack with 7408 AND gate.

As well as a 74LS08 (or equivalent), it’s also possible to use the more common 74LS00 (or equivalent), you just have to use two logic gates instead of one. I’ll post a schematic later.

Mark

1024MAK wrote: ↑Thu Oct 31, 2019 7:52 pm As well as a 74LS08 (or equivalent), it’s also possible to use the more common 74LS00 (or equivalent), you just have to use two logic gates instead of one. I’ll post a schematic later.

Mark

I couldn't find any off the schottky diodes nor the 74LS08 so I've got a pair of 74LS00..
The schematic will be really welcome
Thank you again!!!

To be honest I've made this mode with 1N4148 diodes and it works without any issues.

Regarding NAND gates logic, the circuit would be as shown below:

Yeah, it would not surprise me if 1N4148 diodes worked.

Anyway, my diagram for a 7400 / 74LS00 is similar, but I allocated the gates with the use of stripboard in mind: Mark