Logitek 8240.56.1 Expansion Board for ZX81?

[xelalex]

Hi!

I have what appears to be a 64k RAM expansion for the ZX81, made by Logitek. I haven't been able to find any information on this particular board, and would love to make sure it's what I think it is before plugging it in. Is there anything known about this board? Is it actually for the ZX81? If so, in what way can the 64k be used? I assume not everything will be accessible or usable for running code. Also, is there anything known about the company? Based on the label "Computer Systeme", I guess it's German, Swiss, or Austrian.





Kind regards,
Alex

[XavSnap]

HI,

May be an English/US Kit, like Maplin... (Ci mounted on supports)

But, the red points "<>" on the PCB seem to be a Home-made PCB building.

"8240.56.1" =? Year:82 Week:40 #56 release:1

Ever seen "SYSTEME" for US computers.

[1024MAK]

It’s a professionally made PCB, as it has plated through holes and the copper tracks have a HASL (hot air solder levelling). Although the slot on the rear edge connector definitely looks hand made….

It indeed has 64k bytes of RAM. It does not have any bank switching, so most likely maps it’s RAM to 0x2000 (8192) to 0xFFFF (65535) leaving the ROM between 0x0000 and 0x1FFF (8191). That’s 56k bytes available.

It also has a counter for it’s refresh circuitry, so is almost certainly designed for a ZX81 or TS1000.

Mark

[siggi]

Google found: "Full text of "c't (Magazin fuer Computertechnik) 12/1983""

https://archive.org/stream/ct8312/ct8312_djvu.txt

Code: Select all

Zubehör von Logitek 


Druckerinterface für ZX-Spectrum 

LPRINT, LUST, COPY läuft nun auch mit EPSON und Seikosha 
Druckern MX-80, GP-80 usw. Druck ohne Zeitverlust wie bei 
Druckerpuffern ist in Verbindung mit unserem 80 K RAM mög- 
lich. Der deutsche Zeichensatz kann geladen werden. 


Komplett mit Druckerkabel DM 275,— 

Formschönes schwarz eloxiertes Alugehäuse nimmt den Spec- 
trum mit Netzteil auf. Mit Eln/Ausschalter DM 119,— 

Gehäuse wie oben jedoch zusätzlich mit Erweiterungsplatine 

für 5 Karten DM 198,— 

Erweiterungsplatine für 5 Karten DM 98,— 

80 K Speichernachrüstsatz 

ermöglicht eine Vielzahl neuer Anwendungen durch mehr Spei- 
cherplatz DM 198,— 

ZX-81 64 K RAM Modul 

schwarz eloxiertes Alugehäuse, flach an den Sinclair ansteck- 
bar, Port wird durchgeführt DM 198,— 


ZX-81-Stecker DM 10,— Steckergegenstück DM 5,— 

ZX Spectrum 

Stecker DM 12,— Steckergegenstück DM 6,— 

Für unsere Programmkassetten Liste anfordern. 

Deutsche Beschreibung wird mitgeliefert 

Preise incl. MwSt. Vers, per Nachn. zzgl. 6,50 OM Porto u. Verpackung ab Lager Berlin 

• Achtung! Neuheiten! Messeverkauf • 

Besuchen Sie uns bei der Hobbytronic auf dem Stand 
der Fa. Dahms am 26.— 30. Oktober ln Stuttgart. 

Siggi

[xelalex]

Nice find! So this was a Berlin based company, and I lived for almost ten years not far from that address

[xelalex]

I finally got around to testing the Logitek 64k expansion. It seems to be fully working Apparently 48k available, no himem exec.

[David G]

Nice! Back in 1983 I didn't even dream of having that much memory. But in 1984 I got Memotech 32K which was also very fine

What is Himem-exec?

[mrtinb]

What is Himem-exec?

On a ZX81 you can run machine code on the addresses from 0k - 32k.

0k - 8k has the ROM, so fortunately this code can run.

8k - 16k has RAM on a few systems. It can also be filled with an extra custom ROM. Machine code can run here as well.

16k - 32k here is where the 16k RAMpack is, and here you can run machine code.

Above 32k is designed to be used for the display file, and machine code here will not work (except a small subset of instructions). So if you have a 64k RAMpack, the upper 32k can only be used for data.

However there exists a hardware modification hack called M1NOT, which enable the area 32k - 48k to run machine code. This is what Xelalex refers to as Himem-exec.

Memory from 48k - 64k can never execute machine code.