Re: Data Sheets

From: Richard Atkinson (
Date: 2000-02-08 00:39:01

On Mon, 7 Feb 2000, Nicolas Welte wrote:

> Do you have details how the 6721 is connected inside the V364 system? In
> the Magic Voice it is quite hardware intensive: A 6525 controls a gate
> array which then controls the 6721. I couldn't see anything similar in
> the V364, only the Toshiba chip. Okay, maybe one of the ROM chips is the
> gate array, but there's surely no 6525. Any ideas?

No - actually I was thinking about this earlier today as Bo will attest.

In the Magic Voice the gate array has two functions - to perform whatever
arbitration is necessary between the 6525 and the T6721A and to switch in
the ROM using the GAME# and EXROM# lines as has been discussed in the
context of the C128 Z80 processor.

In the V364 the chip that talks to the T6721A is the 8706R0 I
believe. This is decoded using the 'unused' PLA function in the other
machines ($FD20 - $FD2F) and I'm guessing the speech ROM occupies one of
the ROM slots in the machine's architecture, possibly C2 LOW as this would
make it the first ROM to be detected by the startup code and also allow
regular cartridge ROMs to occupy C1 LOW.

Are these two chips the same? They have the same number of pins, but one
was supposedly designed by TI engineers (badly - ask Bil Herd) and the
other by the 264 architects - who may have borrowed its functionality and
added 6525 style ports. Perhaps it is similar to a 6523. Only the original
designers know - I currently have no access to a V364 machine. I posted on
csc only today asking for Bil Herd's whereabouts; perhaps he can help us.


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