Re: NTSC Apple //e mainboard: Connectors?

["David Wilson" <mcs6502@gmail.com>]

Linards Ticmanis wrote:
> The existence of this signal on that pin tells me that if only I could
> manage to find and program a Motorola 68764 type 24-pin EPROM, I'd be
> able to plug that in there and have instant switchable charsets just
> like on the PAL version.

An alternative is to solder a 28 pin socket onto the top of a 24 pin
plug and route the highest address line to a flying lead and attach
that to the switch.

Interestingly (from what I have seen), the Apple IIc uses a 28 pin
socket for its video ROM even though it may have a 24 pin chip plugged
into it if alternate character sets are not required.

> Unfortunately, that EPROM type seems to be quite rare compared to the
> standard 28-pin 2764, and programmers that can handle it are probably
> even rarer... Though I don't really understand why people chose a chip
> with more pins if an equivalent with fewer was available.

Like the IIgs where a 28 pin 1Mbit ROM is used making it difficult to
use a 1Mbit EPROM as that has 32 pins? The 2764 pinout leads seemlessly
into the 27128, 27256 and 27512 which can be an advantage.