Help needed in identifying mods to my Mega 1

[Tickled_Pink]

Just opened up the Mega 1 as I suspected a previous user had upgraded it. There's a toggle switch at the back that doesn't look it belongs there.

 

Does the original (non-STE) Mega 1 have SIMM slots? I suspect not but this one does. It's on a seperate module attached to the rest of the system by two ribbon cables. It also has another wire which has disconnected itself from wherever it was attached. Looking at the memory upgrade board, it looks like it's a ground wire so may have been attached to the shield until I took it apart. Can someone tell me what memory it might have installed? IIRC, no ST could handle more than 4Mb memory. So I suspect that's what it now has installed. The chips on the SIMMs are 5M41001AJ (manufactured by Mitsibushi).

 

The switch at the back of the machine did make me think that it might be a TOS toggle switch but the wires from it are actually going to somewhere under the power board. It appears as though the wires are attached to a large-ish rectangular IC under the board - but before it gets there the wires go through a small box containing an IC (looks like it's a 74HC74). What on earth could this be?

 

Incidentally, the TOS on this machine also appears to have been upgraded to 1.4.

 

How can I tell if this model has a Blitter installed? Did any of the non-STE Megas have Blitters?

 

Note: I don't have access to my ST monitor at the minute.

[Kylev]

Tickled_Pink,

I own a Mega 2. It definitely does not contain any SIMM slots for memory. It sounds like you have an after-market memory upgrade for sure. Sorry I can't be of any help with the toggle switch.

 

Russ

[1024MAK]

There's a toggle switch at the back that doesn't look it belongs there.

The switch at the back of the machine did make me think that it might be a TOS toggle switch but the wires from it are actually going to somewhere under the power board. It appears as though the wires are attached to a large-ish rectangular IC under the board - but before it gets there the wires go through a small box containing an IC (looks like it's a 74HC74). What on earth could this be?

Not sure what the switch does. The 74HC74 is a flip-flop (also known as a latch) circuit - this is a one bit memory, and would be used for selection of / switching of a input to another chip. But I do not know any further details.

 

Does the original (non-STE) Mega 1 have SIMM slots? I suspect not but this one does. It's on a separate module attached to the rest of the system by two ribbon cables. It also has another wire which has disconnected itself from wherever it was attached. Looking at the memory upgrade board, it looks like it's a ground wire so may have been attached to the shield until I took it apart. Can someone tell me what memory it might have installed? IIRC, no ST could handle more than 4Mb memory. So I suspect that's what it now has installed. The chips on the SIMMs are 5M41001AJ (manufactured by Mitsibushi).

No the Mega did not come with SIMM slots, you have a very common after market upgrade. Most of these had a green and yellow, or just a green colour wire that you are suppose to connect to a grounded piece of the metalwork (that acts as a screen). I do indeed believe that the SIMMs you talk about have should give you 4Mbyte of RAM memory.

 

Incidentally, the TOS on this machine also appears to have been upgraded to 1.4.

This is another very common upgrade.

 

How can I tell if this model has a Blitter installed? Did any of the non-STE Megas have Blitters?

See http://www.atarimagazines.com/startv2n3/mega4.html

 

Hope this helps

[+DarkLord]

With the possible exception of the early Mega ST 1's, I believe

all Mega ST's have the blitter chip.

 

I know every Mega ST2 and Mega ST4 I've seen has it.

 

HTHs.

[1024MAK]

With the possible exception of the early Mega ST 1's, I believe

all Mega ST's have the blitter chip.

The Mega 1 that I have does have a blitter chip.

[Lynxman]

The chips on the SIMMs are 5M41001AJ (manufactured by Mitsibushi).

 

Mitsubishi memory chips works fine with Atari computers.

 

5M41001 = 1Mx1

 

There should be 8 or 9 of this chips mounted on each Simm.

This kind of Simm is 1MByte.

 

There should be 2 or 4 of it.