I finally got around to desoldering the prom from the board and
replacing it with the 28-Pin Socket and retried the program and it
worked FLAWLESSLY! ;( (THANK GOD!)

 So my question is this:  I have a 512KB EPROM on hand and I "WOULD
LIKE" to utilize it with the cartridge in the form of a "MENU DRIVEN
BASE" of some form.

 Something like this....... When you insert the cart and power up the
C= the menu will automatically load up showing the conbtents of the
other programs that are on the cartridge. Then by selecting (Oh I
dunno..... up/down--- F1/F3   whatever combination  you can think of)
you can select the program that resides in that particular portion of
memory on the eprom and RUN IT DIRECTLY FROM THE CART THROUGH THE
MENU!

  Is that possible with the Magic Desk or would I HAVE TO purchase the
64 NIC+?  I do plan on purchasing it in the near future anyways, but
as of now I'm just asking "WHAT IF's." ;)


  Any responses to this would be greatly appreciated.

  Have a great weekend!

  Charles>8-Bit Designs

"ramswell" <shifty_butch@hotmail.com> wrote in message 
news:d8ae7504-6dcb-4889-967e-9ec9421f2497@k38g2000pro.googlegroups.com...
>
> I finally got around to desoldering the prom from the board and
> replacing it with the 28-Pin Socket and retried the program and it
> worked FLAWLESSLY! ;( (THANK GOD!)
>
> So my question is this:  I have a 512KB EPROM on hand and I "WOULD
> LIKE" to utilize it with the cartridge in the form of a "MENU DRIVEN
> BASE" of some form.
>
> Something like this....... When you insert the cart and power up the
> C= the menu will automatically load up showing the conbtents of the
> other programs that are on the cartridge. Then by selecting (Oh I
> dunno..... up/down--- F1/F3   whatever combination  you can think of)
> you can select the program that resides in that particular portion of
> memory on the eprom and RUN IT DIRECTLY FROM THE CART THROUGH THE
> MENU!
>
>  Is that possible with the Magic Desk or would I HAVE TO purchase the
> 64 NIC+?  I do plan on purchasing it in the near future anyways, but
> as of now I'm just asking "WHAT IF's." ;)
>
>
>  Any responses to this would be greatly appreciated.
>

Your problems are manifold.

For a start the magic desk cartridge isn't wired to use a 512k EPROM. It 
takes more than just a 28 pin socket to make that happen, the board would 
need some extensive hacking as it wired to use 4x2764 EPROMs and the 
additional lines required are tied high and that would have to be sorted 
before you soldered in the sockets but...

Then your problem is that the glue logic controlling the bank selection 
would also need to be hacked, all the ROMs removed and the whole lot rewired 
to the single 512k EPROM. But that would still only give you max 32K or so 
(without analysing the schematic but that would be my guess) as that is all 
that the bank selection logic can control as it is.

Then you would have to write the sofware that controls the bank selection 
and put that in one of the banks. Dunno how handy you are at assembler...

Well, it could be done I suppose, but... would you really want to given 
that's not exectly a simple project? I thought the 64NIC+ also uses a 
hardware switch to allow you to select which program (bank) you want to 
select, and is not menu driven?

Have a look here, if you understand this you might get some idea (a hacking 
project I did a while ago now with the Magic Desk cart).

http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x8k-mod/


You would need to do plenty more.

On Nov 11, 9:43=A0pm, "Clocky" <notg...@happen.com> wrote:
> "ramswell" <shifty_bu...@hotmail.com> wrote in message
>
> news:d8ae7504-6dcb-4889-967e-9ec9421f2497@k38g2000pro.googlegroups.com...
>
>
>
>
>
>
>
> > I finally got around to desoldering the prom from the board and
> > replacing it with the 28-Pin Socket and retried the program and it
> > worked FLAWLESSLY! ;( (THANK GOD!)
>
> > So my question is this: =A0I have a 512KB EPROM on hand and I "WOULD
> > LIKE" to utilize it with the cartridge in the form of a "MENU DRIVEN
> > BASE" of some form.
>
> > Something like this....... When you insert the cart and power up the
> > C=3D the menu will automatically load up showing the conbtents of the
> > other programs that are on the cartridge. Then by selecting (Oh I
> > dunno..... up/down--- F1/F3 =A0 whatever combination =A0you can think o=
f)
> > you can select the program that resides in that particular portion of
> > memory on the eprom and RUN IT DIRECTLY FROM THE CART THROUGH THE
> > MENU!
>
> > =A0Is that possible with the Magic Desk or would I HAVE TO purchase the
> > 64 NIC+? =A0I do plan on purchasing it in the near future anyways, but
> > as of now I'm just asking "WHAT IF's." ;)
>
> > =A0Any responses to this would be greatly appreciated.
>
> Your problems are manifold.
>
> For a start the magic desk cartridge isn't wired to use a 512k EPROM. It
> takes more than just a 28 pin socket to make that happen, the board would
> need some extensive hacking as it wired to use 4x2764 EPROMs and the
> additional lines required are tied high and that would have to be sorted
> before you soldered in the sockets but...
>
> Then your problem is that the glue logic controlling the bank selection
> would also need to be hacked, all the ROMs removed and the whole lot rewi=
red
> to the single 512k EPROM. But that would still only give you max 32K or s=
o
> (without analysing the schematic but that would be my guess) as that is a=
ll
> that the bank selection logic can control as it is.
>
> Then you would have to write the sofware that controls the bank selection
> and put that in one of the banks. Dunno how handy you are at assembler...
>
> Well, it could be done I suppose, but... would you really want to given
> that's not exectly a simple project? I thought the 64NIC+ also uses a
> hardware switch to allow you to select which program (bank) you want to
> select, and is not menu driven?
>
> Have a look here, if you understand this you might get some idea (a hacki=
ng
> project I did a while ago now with the Magic Desk cart).
>
> http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x...
>
> You would need to do plenty more.- Hide quoted text -
>
> - Show quoted text -


  DUDE! THAT'S "AWESOME!" :)    Your WAY BETTER than I am at that kind
of stuff (obviously) as I never would of thought in a million years
that I would need to TOTALLY clean out the ENTIRE BOARD and install
all that stuff on it in order to get it to do anything other than the
designed functions.
 So those eproms that you installed are ALL 2764's?  Also, the switch
that you installed there; does that switch banks between the four
eproms?
 This is something that I might still be interested in doing in the
future sometime, but my interest is in the "LARGER" eproms due to what
my desire to accomplish is.

 What I would "LIKE" to do is get it to where it "RUNS GEOS" on it
from the cartridge! I know that's asking QUITE A LOT, but that is what
I want to do. Also, I would like to get the banks to switch between
games and utilities so I can put Montazuma's Revenge, Mighty Bomb Jack
and Mr. Do on the games section and put Omega-Q 2, GEOS, and Novaterm
9.6 on the Utilities section.

 So you can see why I was asking if this was either at all "possible,"
or if it's even something I even want to bother myself with even doing
at all (like you said <the labor, time, effort and all and STILL NOT
GETTING WHAT I WANT out of it>).  :(:(

 So I guess I will go ahead and "REMOVE EVERYTHING" and try and get a
hold of a few 2764 eproms and install them onto the board and go from
there by following your diagram and instructions and see what I can do
at that point.

 This is VERY INFORMATIVE and GREATLY APPRECIATED!

  Thanks a lot! ;)


   Charles

Hallo Clocky,


> http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x...

I can be completely wrong but I think there is an error in your
schematic. You connect the dipswitches to pin 4, 5, 6 and 7 of the
former 74LS138. But 4, 5 and 6 are inputs of the 138 and therefor
cannot select the (EP)ROMs. I would have expected the dipswitches to
be connected to 7, 9, 10 and 11 and that is also what the photos show
(more or less) IMHO.

But seeing the photos my first question was: why did you want to
replace the 138 with switches? And if you wanted switches, why didn't
you connect them to the 138; you then only needed two and wouldn't run
the risk of selecting two or more at the time.

The 74LS175 is a 4-bits latch and let's assume that these bits have
been connected to the data bus. IMHO two of the bits are used to
select the (EP)ROMs. Which leaves us with two free bits: these can be
used to control two extra address lines which enable you to use 27256s
instead of 2764s. Piggyback an extra 175 on top of the original one
and you can use 27512s and still have three free bits for ..... (just
use you imagination :).


Groetjes, Ruud Baltissen
http://www.Baltissen.org

On Nov 12, 12:30=A0pm, Ruud <ruud.baltis...@gmail.com> wrote:
> Hallo Clocky,
>
> >http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x...
>
> I can be completely wrong but I think there is an error in your
> schematic. You connect the dipswitches to pin 4, 5, 6 and 7 of the
> former 74LS138. But 4, 5 and 6 are inputs of the 138 and therefor
> cannot select the (EP)ROMs. I would have expected the dipswitches to
> be connected to 7, 9, 10 and 11 and that is also what the photos show
> (more or less) IMHO.
>
> But seeing the photos my first question was: why did you want to
> replace the 138 with switches? And if you wanted switches, why didn't
> you connect them to the 138; you then only needed two and wouldn't run
> the risk of selecting two or more at the time.
>
> The 74LS175 is a 4-bits latch and let's assume that these bits have
> been connected to the data bus. IMHO two of the bits are used to
> select the (EP)ROMs. Which leaves us with two free bits: these can be
> used to control two extra address lines which enable you to use 27256s
> instead of 2764s. Piggyback an extra 175 on top of the original one
> and you can use 27512s and still have three free bits for ..... (just
> use you imagination :).
>
> Groetjes, Ruud Baltissenhttp://www.Baltissen.org


 Possible that you might be able to send me a schematic of some sort
showing me how I could do this? As I DO DESIRE to run the 512 rather
than having to go out and get all this stuff I don't have on hand
right now.

  Thanks Ruud!

  Charles

On Nov 12, 12:30=A0pm, Ruud <ruud.baltis...@gmail.com> wrote:
> Hallo Clocky,
>
> >http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x...
>
> I can be completely wrong but I think there is an error in your
> schematic. You connect the dipswitches to pin 4, 5, 6 and 7 of the
> former 74LS138. But 4, 5 and 6 are inputs of the 138 and therefor
> cannot select the (EP)ROMs. I would have expected the dipswitches to
> be connected to 7, 9, 10 and 11 and that is also what the photos show
> (more or less) IMHO.
>
> But seeing the photos my first question was: why did you want to
> replace the 138 with switches? And if you wanted switches, why didn't
> you connect them to the 138; you then only needed two and wouldn't run
> the risk of selecting two or more at the time.
>
> The 74LS175 is a 4-bits latch and let's assume that these bits have
> been connected to the data bus. IMHO two of the bits are used to
> select the (EP)ROMs. Which leaves us with two free bits: these can be
> used to control two extra address lines which enable you to use 27256s
> instead of 2764s. Piggyback an extra 175 on top of the original one
> and you can use 27512s and still have three free bits for ..... (just
> use you imagination :).
>
> Groetjes, Ruud Baltissenhttp://www.Baltissen.org


 You got some RAD STUFF on your site man!

  I downloaded lots of it for "future" projects! ;)

 Know where I may be able to get my hands on a 1541 PCB board?  I want
to "try" that IDE 41 project out.


  Thanks again and have a great weekend!

  Charles

Ruud wrote:
> Hallo Clocky,
>
>
>> http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x...
>
> I can be completely wrong but I think there is an error in your
> schematic. You connect the dipswitches to pin 4, 5, 6 and 7 of the
> former 74LS138. But 4, 5 and 6 are inputs of the 138 and therefor
> cannot select the (EP)ROMs. I would have expected the dipswitches to
> be connected to 7, 9, 10 and 11 and that is also what the photos show
> (more or less) IMHO.
>

It's 74LS139  4,5,6,7 are data outputs that go to the EPROM select lines.

> But seeing the photos my first question was: why did you want to
> replace the 138 with switches? And if you wanted switches, why didn't
> you connect them to the 138; you then only needed two and wouldn't run
> the risk of selecting two or more at the time.
>

139 ;-)

> The 74LS175 is a 4-bits latch and let's assume that these bits have
> been connected to the data bus. IMHO two of the bits are used to
> select the (EP)ROMs. Which leaves us with two free bits: these can be
> used to control two extra address lines which enable you to use 27256s
> instead of 2764s. Piggyback an extra 175 on top of the original one
> and you can use 27512s and still have three free bits for ..... (just
> use you imagination :).
>

Time and skill, or lack thereof are a factor.

I've learned a lot from doing those projects, the Creativision multicart was 
a better effort :-) 

Il 13/11/2011 00:30, Clocky ha scritto:

>
> It's 74LS139  4,5,6,7 are data outputs that go to the EPROM select lines.
>
>> But seeing the photos my first question was: why did you want to
>> replace the 138 with switches? And if you wanted switches, why didn't
>> you connect them to the 138; you then only needed two and wouldn't run
>> the risk of selecting two or more at the time.
>>
>
> 139 ;-)

I was thinking along the same lines... keeping the 74* logic, passing 
from an eprom to another became machine-controllable, seems to me...

Best regards from Italy,
dott. Piergiorgio.

dott.Piergiorgio wrote:
> Il 13/11/2011 00:30, Clocky ha scritto:
>
>>
>> It's 74LS139  4,5,6,7 are data outputs that go to the EPROM select
>> lines.
>>> But seeing the photos my first question was: why did you want to
>>> replace the 138 with switches? And if you wanted switches, why
>>> didn't you connect them to the 138; you then only needed two and
>>> wouldn't run the risk of selecting two or more at the time.
>>>
>>
>> 139 ;-)
>
> I was thinking along the same lines... keeping the 74* logic, passing
> from an eprom to another became machine-controllable, seems to me...

You will note that the option is still there to do just that.

If I was a more proficient programmer and I had more time, then that would 
be the next step.

On Saturday, November 12, 2011 11:09:58 PM UTC-8, Clocky wrote:
> dott.Piergiorgio wrote:
> > Il 13/11/2011 00:30, Clocky ha scritto:
> >
> >>
> >> It's 74LS139  4,5,6,7 are data outputs that go to the EPROM select
> >> lines.
> >>> But seeing the photos my first question was: why did you want to
> >>> replace the 138 with switches? And if you wanted switches, why
> >>> didn't you connect them to the 138; you then only needed two and
> >>> wouldn't run the risk of selecting two or more at the time.
> >>>
> >>
> >> 139 ;-)
> >
> > I was thinking along the same lines... keeping the 74* logic, passing
> > from an eprom to another became machine-controllable, seems to me...
>=20
> You will note that the option is still there to do just that.
>=20
> If I was a more proficient programmer and I had more time, then that woul=
d=20
> be the next step.


 By the way Clocky, I've been also meaning to ask yopu if it is at all poss=
ible for you to "SHOW ME WHERE" you placed the connections for the switches=
 on this project as all I can see from the photo is a ribbon cable sliding =
underneath the U3, but it doesn't show where the pins connect unfortunately=
..
 I've gotten my hands on 4 2764's and they are all socketed, I performed al=
l the other necessary steps according to your instructions, cutting the jum=
pers, etc., and I've soldered on the 4 resistors (for the switch I assume) =
onto the socket.
 So now I just have to figure out where the pins go for the switch and I ca=
n begin the testing of it.
  Any help with this would be greatly appreciated whenever you get the time=
..
  Take care,

  Charles

On Friday, November 11, 2011 9:43:42 PM UTC-8, Clocky wrote:
> "ramswell" <shifty_butch@hotmail.com> wrote in message=20
> news:d8ae7504-6dcb-4889-967e-9ec9421f2497@k38g2000pro.googlegroups.com...
> >
> > I finally got around to desoldering the prom from the board and
> > replacing it with the 28-Pin Socket and retried the program and it
> > worked FLAWLESSLY! ;( (THANK GOD!)
> >
> > So my question is this:  I have a 512KB EPROM on hand and I "WOULD
> > LIKE" to utilize it with the cartridge in the form of a "MENU DRIVEN
> > BASE" of some form.
> >
> > Something like this....... When you insert the cart and power up the
> > C=3D the menu will automatically load up showing the conbtents of the
> > other programs that are on the cartridge. Then by selecting (Oh I
> > dunno..... up/down--- F1/F3   whatever combination  you can think of)
> > you can select the program that resides in that particular portion of
> > memory on the eprom and RUN IT DIRECTLY FROM THE CART THROUGH THE
> > MENU!
> >
> >  Is that possible with the Magic Desk or would I HAVE TO purchase the
> > 64 NIC+?  I do plan on purchasing it in the near future anyways, but
> > as of now I'm just asking "WHAT IF's." ;)
> >
> >
> >  Any responses to this would be greatly appreciated.
> >
>=20
> Your problems are manifold.
>=20
> For a start the magic desk cartridge isn't wired to use a 512k EPROM. It=
=20
> takes more than just a 28 pin socket to make that happen, the board would=
=20
> need some extensive hacking as it wired to use 4x2764 EPROMs and the=20
> additional lines required are tied high and that would have to be sorted=
=20
> before you soldered in the sockets but...
>=20
> Then your problem is that the glue logic controlling the bank selection=
=20
> would also need to be hacked, all the ROMs removed and the whole lot rewi=
red=20
> to the single 512k EPROM. But that would still only give you max 32K or s=
o=20
> (without analysing the schematic but that would be my guess) as that is a=
ll=20
> that the bank selection logic can control as it is.
>=20
> Then you would have to write the sofware that controls the bank selection=
=20
> and put that in one of the banks. Dunno how handy you are at assembler...
>=20
> Well, it could be done I suppose, but... would you really want to given=
=20
> that's not exectly a simple project? I thought the 64NIC+ also uses a=20
> hardware switch to allow you to select which program (bank) you want to=
=20
> select, and is not menu driven?
>=20
> Have a look here, if you understand this you might get some idea (a hacki=
ng=20
> project I did a while ago now with the Magic Desk cart).
>=20
> http://users.on.net/~clockmeister/other/EPROM-Cartridge/Magic-Desk-4x8k-m=
od/
>=20
>=20
> You would need to do plenty more.






  Hey Clocky, could you please do me a favor and give me the details of "wh=
ere exactly" these dip switch conncetions go to? I've connected them to the=
 resistors inside the 16-pin dip socket and nothing happened so I think I m=
ay have done something incorrectly someplace. I still need to install the p=
ower switch as well (which is a bridge I will cross after I figure out wher=
e the dip switches go to) naturally.
  All help is greatly appreciated, as has been all your past ideas! ;)

  Thanks a lot!

  Charles