Amstrad/Sinclair PC200 dualscreen

Last Updated or created 2023-07-28

While doing some wood work, routing and painting. I managed to have some time to experiment with my PC200.

The Amstrad PC20 / Sinclair PC200 was a home computer created by Amstrad in late 1988. The machine was available in two versions, Sinclair PC200 and Amstrad PC20. (US/UK?)

In addition to MS-DOS 3.3 and PPC Organiser (a memory-resident suite of utilities), the PC20/PC200 was supplied with GEM. (I do not have those disks)

The limited CGA graphical capabilities and PC speaker sound output were greatly inferior compared to other home computers of the time.
I has a modulator to connect a TV and could do hercules graphics on a sub-9 interface.

I got this computer a long time ago. (I still have to post pictures of my collection and getting them out of storage)

Info about this machine:

Build in 1988, Intel 8086 @ 8Mhz 512KB memory 3.5″ Floppy drive
TV Modulator Pal 640×200 CGA and Hercules


It still had a floppy in its drive, NIMMO Disk Juli 1992

Apparently this machine was used with a modem to do some interviewing for the University Amsterdam using Telepanel/Interview!

The ROM has several language options which you could set with dipswitches.

Debug part of ROM

Besides the machine having a “amiga” like case, it has two ISA slots behind a little trapdoor! How cool is that!

Dirty view of the ISA slots (One containing a RTC card)

Enabling only CGA on the machine and plugging in a Hercules card, you can do Multiscreen!
CGA and MDA addresses don’t conflict!
And if the ROM supports it .. dual screens baby!

Left Hercules and Right CGA

I used a debug command to fill the right screen

f b800:0 1000 ‘f a s h’

Cool little machine

Running old masm/precompiled machine code crashes. I’ll have to look into that.

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