Something into a Mega ST

[Guillaume Tello]

Hi,

Can anyone tell me what's in this Mega ST ??
I suppose it's an accelerator, but QuickIndex doesn't show a better
speed than a normal 8MHz ST.
Is there a software to activate this clock?

Loading Image...

Guillaume.

[Michael Schwingen]

Post by Guillaume Tello
Can anyone tell me what's in this Mega ST ??
I suppose it's an accelerator, but QuickIndex doesn't show a better
speed than a normal 8MHz ST.
Is there a software to activate this clock?
http://pagesperso-orange.fr/gtello/megast.png

That's the "blitter fix" - a patch that was fitted by Atari to avoid crashes
with certain series of blitter chips.

If you have no blitter, or if the blitter does not have the problem, the PCB
can be completely removed, but you have to re-attach one PCB trace (on
bottom side of PCB, somewhere under the CPU) that was cut when adding the
fix.

cu
Michael

[phantomm_1]

How can you tell if your MegaST has the bad Blitter?

Is there a certain program that you can run?


Also, were there any problems with Grounding on some of the
MegaSTs?

If so, any trouble spots/fixes would be helpful.

Barry

Post by Michael Schwingen

Post by Guillaume Tello
Can anyone tell me what's in this Mega ST ??
I suppose it's an accelerator, but QuickIndex doesn't show a better
speed than a normal 8MHz ST.
Is there a software to activate this clock?
http://pagesperso-orange.fr/gtello/megast.png

That's the "blitter fix" - a patch that was fitted by Atari to avoid crashes
with certain series of blitter chips.
If you have no blitter, or if the blitter does not have the problem, the PCB
can be completely removed, but you have to re-attach one PCB trace (on
bottom side of PCB, somewhere under the CPU) that was cut when adding the
fix.
cu
Michael

[Michael Schwingen]

Post by phantomm_1
How can you tell if your MegaST has the bad Blitter?

First check if it has any blitter at all ;-)
I think there were lists in the german chips&chips hypertext. Other than
that, you could probably just try if it is stable without the fix.

If you do not need access to the CPU pins to install some upgrade, just
leave it as it is.

If you do want to upgrade the machine, simply throw out both the fix and the
blitter. Optimized VDI code (like NVDI) is actually faster than the blitter,
so this is no real loss, especially if you install a CPU upgrade.

Post by phantomm_1
Also, were there any problems with Grounding on some of the
MegaSTs?

None that I remember. Do you have problems with the machine?

ycu
Michael

[phantomm_1]

Post by Michael Schwingen

Post by phantomm_1
How can you tell if your MegaST has the bad Blitter?

First check if it has any blitter at all ;-)
I think there were lists in the german chips&chips hypertext. Other than
that, you could probably just try if it is stable without the fix.
If you do not need access to the CPU pins to install some upgrade, just
leave it as it is.
If you do want to upgrade the machine, simply throw out both the fix and the
blitter. Optimized VDI code (like NVDI) is actually faster than the blitter,
so this is no real loss, especially if you install a CPU upgrade.

Post by phantomm_1
Also, were there any problems with Grounding on some of the
MegaSTs?

None that I remember. Do you have problems with the machine?
ycu
Michael

I have a MegaST here that I've been tinkering with.
I have a few upgrades that I can install, one being a JRI Genlock.
I also have a large board that I bought from e-bay some time ago,
It was advertised as being a Memory upgrade board, I'm not sure
what it is. It's a very long board that plugs into the mega board expansion
socket and has a port that goes out to the back of the mega where the little
slide door is. It's a 9 pin connection.

The board has ATR-4CP Rev A3 on it, also Image Systems Corp. 1989
Made in USA.

There is also a 64 pin connection on top of the board.
There are alot of chips on this board.
The only square socket chip is labled Bt Bt454KPJ.
I notice a 65mhz clock? on it, also has 2 empty sockets. One large
Square one with a small one next to it. The large socket has round
type holes, looks like for a chip with round pins fits into it.

It also has a 6 pin wire connection and came with a cable that fits
it.
I didn't get any instructions with it, but was advertised to me as a
large Memory upgrade board.

I was told it came out of a MegaST and did work.

I'd like some info on it, what it actually is and does do.
I can provide pics if that will help.


Also, a question regarding the MegaSTs Video Shifter Chip.
When putting one in the MegaST, does the writting on the chip
look upside down when compaired to the other chips around it?

I'm not sure if the socket for the shifter is put in backward or not
going by the Pin 1 Notch on the socket and chip.

I don't want to put the chip in the wrong way, in other words.

Barry
***@bellsouth.net

[Jo Even Skarstein]

Post by phantomm_1
I also have a large board that I bought from e-bay some time ago,
It was advertised as being a Memory upgrade board, I'm not sure
what it is. It's a very long board that plugs into the mega board expansion
socket and has a port that goes out to the back of the mega where the little
slide door is. It's a 9 pin connection.
The board has ATR-4CP Rev A3 on it, also Image Systems Corp. 1989
Made in USA.

It's a graphics card, but I don't know anything about it.

[Guillaume Tello]

Yes, the blitter is present!

So this could be a blitter "fix" ?

Guillaume.