El 10/09/2010 15:48, Urs Koenig (QL) escribió:
Well done! Congratulations!
Thanks! :)
BTW: What is the WINBOND Chip in one of the ROM sockets and the
small PCB in the other ROM socket? Is the WINBOND a PROM and
the small PCB a switch for two or more OS?
It's a simple way of having Minerva and Toolkit MKII in one chip. The Winbond
chip is a 64Kx8 EEPROM, placed in one of the original ROM sockets. Some pins are
bended out and wired to a small decoder built on the small PCB, that uses the
original signals to generate proper enable signals to the EEPROM.
The jumper you see closed enables the Toolkit MKII. If you want to use the
external ROM expansion, open that jumper and you will able to plug another
expansion ROM.
This is a modification of a Minerva replacement PCB designed and built by Jose
Leandro Novellon.
http://trastero.speccy.org/cosas/JL/ROM-EPROM_QL/ROM-EPROM-QL.html
His design needs low profile sockets, more pins, and does not offer the ability
to use the remaining 16K memory offered by a 64K device. On the other hand, it's
a plug'n'play option.
My option is a bit rough, with wires coming from one place to another, but the
PCB is far easier to do, and there's no need for low profile sockets, as long as
you don't mind soldering the 74LS00 directly to the PCB.
You can read a full description of this design here (spanish). You can even
built it with a breadboard PCB, as you can see in the first post of the thread.
A few posts later, you will find the updated design, as you have seen.
http://www.speccy.org/foro/viewtopic.php?f=15&t=2000
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