VTech Socrates – Speech Emulation Progress and French Speech ROMs Successfully Dumped!

Another exciting breakthrough in VTech Socrates preservation!

Today, we made significant progress extending the MAME Socrates driver with support for the Toshiba TC8802AF speech synthesizer. At the same time, we developed a custom cartridge ROM that allows us to read and verify the speech ROM contents directly on original hardware.

And the best part? We successfully dumped and verified both speech ROMs from the French Socrates!

Turning the Socrates Into Its Own ROM Dumper

The Socrates speech hardware uses a dedicated Toshiba speech synthesizer (tc8802) with internal ROM and support for additional external Voice Synthesis Memory (VSM).

Unlike ordinary cartridge ROMs, these memories cannot simply be read through the console's normal address bus. Instead, they must be accessed through the speech chip's command interface.

Our solution was to develop a custom Z80 cartridge ROM that communicates directly with the speech synthesizer and displays its memory contents on the television screen.

The dumper supports two memory regions:

• INTERNAL: The 8 KB internal mask ROM, accessed using read condition 00. Its contents are displayed across 32 pages of 256 bytes each.

• EXTERNAL: The complete 64 KB external VSM address space (4 x 16kb), accessed using read condition 04, displayed across 256 pages of 256 bytes each.

Each page displays the extracted bytes as hexadecimal values, together with a SUM16 checksum in the footer.

 

To make the results even more reliable, we implemented a second complete reading pass. The program compares the results against the first pass and displays OK or ERROR in a dedicated column.

 

This makes it possible to detect unstable reads directly on the original console!

Built-In Checksum Verification

One of the most useful features is the integrated checksum calculation.

The dumper calculates both SUM16 and standard ZIP-compatible CRC32 checksums for the internal ROM and all four external VSM memory regions.

This allows direct comparison with the CRC32 values used by MAME.

It also reads the identification sequence A5 53 4F, displaying the identification text SOCRATES,VTEL88.

The read timing can be adjusted by changing the delay after each START transition, which is particularly useful when testing the stability of the speech hardware.

Combined with the second reading pass, these features make the dumper much more than a simple hexadecimal viewer. It is a practical hardware verification tool.

Dumper Controls

The entire program can be operated using the original Socrates controller.

Button	Function
Left directional pad	Previous / next page (±1)
Right directional pad	Jump backward / forward by 16 pages
Left red button	Switch between INTERNAL, EXTERNAL and CHECKSUM screens
Right red button	Toggle automatic page advancement in hexadecimal display mode
Right red button (checksum screen)	Restart the complete measurement
Left directional pad (checksum screen)	Adjust the delay after each START transition

The automatic page advancement feature changes the displayed page every 2 seconds, making it especially useful when recording the ROM contents using a video capture card.

Rather than manually stepping through hundreds of screens, the console can automatically display the entire memory region while the capture device records the output.

The screenshots can then be processed on a PC to reconstruct the original binary ROM images, with each page checked against its displayed SUM16 value.

The French Speech ROMs – Successfully Recovered!

Using this new dumper on original French Socrates hardware, we successfully recovered both populated speech memories.

ROM	Size	CRC32
speech_fra_internal.bin	8 KB	D08310A3
speech_fra_vsm1.bin	16 KB	B1146420

The French speech cartridge uses only VSM1. VSM2, VSM3 and VSM4 are not populated, so there is no additional speech data to recover from those positions.

Both ROMs were read and verified multiple times, with consistent results. The reconstructed data also matched the checksums reported by the dumper.

This confirms a complete, verified 24 KB speech ROM set for the French Socrates!

What's Next?

With the French speech ROMs successfully preserved and the MAME driver now being extended to support the speech hardware, we are moving closer to accurately reproducing the original Socrates speech capabilities.

The custom dumper will also be extremely useful for checking other regional speech cartridges, comparing ROM revisions, and validating additional speech hardware.

Nearly 38 years after the Socrates was released, another missing piece of its history has finally been preserved.

The Socrates is getting its voice back!