Sinclair ZX80 / ZX81 / Z88 Forums

I can do that if you like. There were 8 additional chips at the board and 2 additional at the Vdrive2 adapter needed. Final state.jpg Front.jpg Left.jpg With Vdrive2.jpg This is the output of Vdrive2 info. You may notice changed character set. I copied ROM to RAM and replaced number characters. Vdri...

Jumper implemented. In general I am able to switch 8-16k area now between WRX and UDG RAM. Dungeons of Ymir andf Invaders are loading now, Unfortunately they REALY need entire 8-16k so they are not compatible with my Vdrive2 driver(residing at write protected 8-10k). I assume that I will proof them ...

Thank you Siggi for that hint. I had seen that page, but didn't notice that these programs need WRX RAM between 8-16k. I checked Dungeons of Ymir and Invaders from Fred's page and both gave me puzzled signs. So it seems that it is impossible to run all with one configuration. I will add a jumper to ...

Best of both worlds (WRX and UDG) ! As you may know WRX HRG is using CPU addressing in RAM with I and R Register as pointer to High res data. UDG and CHR$128 use a combination of a line counter and the content of DFILE to address character pattern in RAM. Both are not compatible to each other. So or...

http://web.archive.org/web/20150907000745/http://bitcycle.org/retro/zx81/internal_RAM/ is a quite good how-to to start with internal ram expansion. It is near to the way i started with two differences: I did not cut any line on the board but cut the legs of the socket that doesn't fit to the right ...

Let's start with the assumption that a Timex Sinclair 1000 is identical to a ZX81 except of the size of the RAM. So you may implement the solution I did. This will give you 24k of UDG enabled RAM and 32k of WRX eneabled RAM. ZX81 56k.jpg the design is based on this https://forum.tlienhard.com/phpBB3...

External RAM pack usually disable internal RAM by pulling /RAMCS to high.
So I would expect no difference if internal RAM is missing and external RAM is attached.

Max

Hero(hero.p) tested as working with Minstrel 3 + 56k.

I had some issues with my TFT monitor running Minstrel in PAL mode when Hero was loaded.
This could be solved by switching to NTSC mode(even if I am in Europe).

Max

There are a couple of solutions out there how to expand ZX81(that is nearly identical if I am right) to more than 32k. Form my point of view you need some decisions first: - Are you interested in High Res - If yes, are you fine with WRX High Res only(possible with 1 RAM chip) or do you like to imple...

Step 2 CHR$128: In the first step I already implemented UDG capability into MInstrel 3. So what is the difference between UDG and CHR$128? Both are using customized character-sets located in RAM. Within RFSH cycle both are building pattern address based on line counter and character in DFILE. UDG is...