One Meg





Very simple - One Megabyte of memory on an expansion card.

The memory could not be accessed from Basic but could be paged in at machine code level and was most useful to use as a RAM Disc with MasterDOS.

Most users with the One Meg also had a SamBus or a Two-up/Three-up interface expansion unit.

On the circuit board there is a jumper connection (bottom left above the capacitor) to allow a one from four position selection (which is factory set to position four). This enables up to four 1 Mb External Interfaces to be connected together giving a possible total memory capability of 4.5 Megabytes of RAM (4,718,592 bytes)

A few products utilised the extra memory such as E-Copier by Chris White and Sam Paint.

PDF Manual Scan at


1MB memory for the Sam

Completely useless!! As useless as a Kaleidoscope (someone just mention something???) We havent heard any details about the ever so useless Kaleidoscope yet! 32,000 colors on an 8-Bit computer? Yeah - right, pull the other one!

Maybe the 1MB of memory & the much fabled Kaleidoscpe (built properly this time!) would have worked wonders together if software developers actualy made use of them!! Like the Sam computer the 1MB memory is a total waste of good technology!!


The ‘Kaleidoscope’ was the example application of the Hardware Development Kit which was sold in the press as “Allowing 32768 colours” but in reality was just a tinkerers toy with resistors pulling down the RGB lines on the output.

As for the Meg - depends whether you had one or not really :)

The 800kB RamDisc was very, very useful as a virtual second drive for copying discs via the BACKUP command.

I modified many programs like Sam C to use the Ram disc for holding the libraries for compilation which was ace.

One of the most useful

One of the most useful pieces of SAM hardware if you where involved in software production .. together with a second floppy drive and copy of MasterDos :)


At my page
is full documentation for 1MB interface for SAM COUPE.
CPB,schematic and equations for GAL16V8

ports for 1mb

u cant use mem$ to break the top 32768 into two 16kb chunks page in external 1-4mb into hmpr cd and then poke the string back into it ?

The 1 Mb External Memory is controlled by two 8-bit registers
which are adressed by port 128 for the first PAGE (EXPAGE-C,
8000 hex to BFFF hex) and port 129 for the second PAGE
(EXPAGE-D, 0000 hex to FFFF hex). As you can see, when the
external memory is switched in, it replaces the top 32k of the
processor addressable memory.

not possible to put all 48 emulator top 32768 bytes into external 1mb somehow - for multiface snaps and +d especially .kul emualtor file as that is the only version of f16 we have - which still doesnt work properly either!

just so u know!

similar effect:

BORDER port (254 dec)
This output port mainly controls the border colour of the screen by
supplying a 4-bit address to the Colour Look Up Table (CLUT), to enable
a colour to be displayed during border time.
Bit 0 BCD 1 of CLUT address for border colour.
Bit 1 BCD 2 of CLUT address for border colour.
Bit 2 BCD 4 of CLUT address for border colour.
Bit 3 MIC output control bit, normally set high.
Bit 4 BEEP output control bit, normally set low.
Bit 5 BCD 8 of CLUT address for border colour.
Bit 6 THROM bit set high to allow through MIDI operation
Bit 7 SOFF bit set high to disable screen display, only
active in screen modes 3 and 4, also re
moves memory contention during off period.

screen$ off in modes 3/4 not mode 2 or 1

1MB external ram interface

is anyone working on getting the external ram interface to page its ram into the bottom LMPR A,B sections of ram please
if this is possible then surely the z80 version of bbc basic will run at the full 6MHz, by the way it has a built in z80 assembler:

also the currah micro source rom interface

two disks from the velesoft site get zx spectrum 48K and one 128K programs running at the full 6MHz

and of course CP/M which like windows doesn’t know what the screen resolution is or if there’s a tv tuner in the machine

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