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Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Thu May 19, 2022 9:55 pm
by 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
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Fri May 20, 2022 1:22 am
by 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.
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Fri May 20, 2022 1:45 am
by 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
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Fri May 20, 2022 9:34 am
by 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
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Fri May 20, 2022 11:18 am
by xelalex
Nice find! So this was a Berlin based company, and I lived for almost ten years not far from that address
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Sat May 28, 2022 5:12 pm
by xelalex
I finally got around to testing the Logitek 64k expansion. It seems to be fully working
Apparently 48k available, no himem exec.
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Sun May 29, 2022 1:36 pm
by 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?
Re: Logitek 8240.56.1 Expansion Board for ZX81?
Posted: Sun May 29, 2022 2:06 pm
by mrtinb
David G wrote: ↑Sun May 29, 2022 1:36 pm
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.