Search found 2622 matches

by 1024MAK
Sun Jan 19, 2020 12:17 am
Forum: GAMES
Topic: Level 9 Adventure Games
Replies: 3
Views: 27

Level 9 Adventure Games

In late 1982 / early 1983, Level 9 released some adventure games for a number of machines, and apparently this included 16K versions for the ZX81. https://i.postimg.cc/JD95gPSd/level9-1982.png https://i.postimg.cc/MX0vQ9dZ/level9b.png Does anyone have any memories of these games on the Zeddy, or bet...
by 1024MAK
Sat Jan 18, 2020 9:45 pm
Forum: WANTED
Topic: SD card reader for ZX81
Replies: 7
Views: 325

Re: SD card reader for ZX81

The ZXpand+ interface (and the earlier ZXpand interface) do allow files to be saved to the SD card.

Mark
by 1024MAK
Tue Jan 14, 2020 7:39 pm
Forum: Hardware
Topic: Improvised 32K RAM?
Replies: 6
Views: 166

Re: Improvised 32K RAM?

Err, from that view, it looks like they have piggybacked on top of the original SRAM chip! :shock:
So only 8k bytes of extra memory :(

Mark
by 1024MAK
Tue Jan 14, 2020 4:14 pm
Forum: Hardware
Topic: Improvised 32K RAM?
Replies: 6
Views: 166

Re: Improvised 32K RAM?

Could be one of two methods of RAM expansion, but the total amount of RAM looks like 16k bytes if it is two 8k byte SRAM chips connected piggy-back style. I’m on a train, and don’t have time to work out further details at the moment. It looks like the solid core wires have broken due to stress fract...
by 1024MAK
Mon Jan 13, 2020 1:11 am
Forum: Hardware
Topic: Homemade German Interface, for what?
Replies: 3
Views: 217

Re: Homemade German Interface, for what?

Yep, that chip is a member of the Z80 family, but it is not a microprocessor. It is a programmable input/output interface chip. If you want more information have a look at the various documents on this site, especially those about the Zilog PIO...

Mark
by 1024MAK
Thu Jan 09, 2020 12:31 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1001

Re: vLA81 ULA and 16/32K internal RAM

Partial address decoding is a bit like someone who is used to the 24 hour clock (00:00 hours through to 23:59 hours) looking at a 12 hour clock. If there is no AM or PM indication, and you can’t see outside (to see if it is daylight) how do you tell if it is 3am or 3pm, as the clock just shows 3:00....
by 1024MAK
Thu Jan 09, 2020 12:11 am
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1001

Re: vLA81 ULA and 16/32K internal RAM

Oh, one VERY important thing that I forgot to mention... Due to the partial address decoding that is used in systems like the ZX81, where there is less than 64k bytes of RAM and ROM fitted, if you POKE an address where there is no unique RAM memory, you may be poking a number elsewhere in RAM! This ...
by 1024MAK
Wed Jan 08, 2020 9:23 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1001

Re: vLA81 ULA and 16/32K internal RAM

Oh, lots of misleading information in that forum thread you linked to :? The system variable “RAMTOP” is in itself not a lot of use as an indication of how much RAM is available after power on if you have more than 16K bytes if RAM fitted in your system. As the ZX81 ROM only looks for up to 16K in t...
by 1024MAK
Wed Jan 08, 2020 9:11 pm
Forum: Development
Topic: ZX81 Clone Tynemouth Minstrel 3
Replies: 18
Views: 1199

Re: ZX81 Clone Tynemouth Minstrel 3

You cannot have RAM enabled in the same area on the Minstrel and the Chroma. Chroma has DIP switches for this. Maybe the Minstrel has some jumpers for this setting on its device. However Chroma might need to have RAM enabled where screen and color is stored, for video output to work through the Chr...
by 1024MAK
Wed Jan 08, 2020 8:57 pm
Forum: Development
Topic: ZX81 Clone Tynemouth Minstrel 3
Replies: 18
Views: 1199

Re: ZX81 Clone Tynemouth Minstrel 3

I don’t see any obvious reason why the Chroma should not work with the Minstrel 3. The only snag maybe if the Chroma is unable to output HC CMOS logic high levels, but that goes for any interface that you want to use (as everything was originally designed for use with TTL logic levels). The Fruitcak...