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Memory organization of the VG5000µ

Advertisement announces VG5000 has 24 KB RAM and 18 KB ROM.

Here are the inscriptions written on the VG5000 case:

ROM (Read Only Memory)

16 KB contains Basic and the BIOS of the VG5000, and the 2 additionnal KB are reserved for the charset (2048 bytes held in the video processor EF9345).
There are 2 versions of the VG5000 ROM, one with Basic v1.0, held in two 8 KB ROM circuits, and one with Basic 1.1, held in one 16 KB ROM circuit.

2 circuits TMS4764 version The doughter board including the 2 ROMS
Here, the daughter board has been removed,
you can insert the 9128C ROM from GI
left side, the 9128C GI ROM

You may notice, that the VG5000 with Basic 1.0 version was planned with only one ROM circuit (16 KB TMS47128). But, because of a lack of supply, the VG5000 will be temporarily equipped with two 8 KB ROM circuits (TMS4764). A few hundreds of units where build with those 2 ROM circuits.

For the 1.1 version, Philips will use a GI 9128C ROM circuit.

GI 9128C ROM circuit datasheet - 16 KB

RAM (Random Access Memory)

VG5000 embeds 24 KB (3 x 8 KB) type SRAM D4168C (200ns)

Memory distribution:
2 x 8 KB : used by the system
1 x 8 KB : used by the video processor

Internal view:

Finally, with a basic version, there are 13758 bytes free available for your program.

basic version with a Basic 1.0 rom basic version with a Basic 1.1 rom

For the programmers, here is the memory map of the VG5000

SRAM D4168C (200ns) Datasheet

VG5216 extension

With the VG5216, 16  KB de RAM are added to the system (as long as joystick, printer and bus extensions). There are 30142 bytes available.

The inscriptions on the VG5216 case:

Internal view:

basic version with VG5216 extension basic version with VG5216 andLgraph*
* Lgraph is a software (Basic) extension to add bitmap capability to printing.

VU0031 cartridge

The VU0031 adds 2 x 8 KB type SRAM D41416C (150ns). There are 46526 bytes available.

The inscriptions on the VU0031 case:

Internal view:

basic version + VG5216 + VU0031 basic version + VG5216 + VU0031 + Lgraph*
* Lgraph is a software (Basic) extension to add bitmap capability to printing.


Configuration commercial total Real Available (for the Basic)
VG5000 24 KB 16 KB 13758 bytes
VG5000 + VG5216 40 KB 32 KB 30142 bytes
VG5000 + VG5216 + VU0031 56 KB 48 KB 46526 bytes

In Basic : PRINT FRE(0) prints the user memory available.

And now ?

To be done:
SRAM D41416C (150ns) [VG5216] Datasheet

Where can you find spare RAM circuits? Answer: in a Sega Master System, it uses the same SRAM circuits.

Upgrade the VG5216 with 2 16 KB RAM circuits to free the cartridge port...

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