Softcard II and AMD AM2950

This datasheet seems for the wrong chip but for one that can serve a similar purpose (mislabelled in the URL I think)

https://www.digchip.com/datasheets/parts/datasheet/013/AM2950-pdf.php

It does mention the chip you're inquiring about to be a parallel IO 8 bit data chip, if I'm reading it right. 

Here is the datasheet: https://www.applefritter.com/files/2023/04/22/AM2950.pdf

If you fill the slots with retro TTL cards, you can definitely exceed the 2.5A nominal current of the +5V rail specified on the PSU. If you are worried, just measure it. Here is my Pravetz 82 (Apple II+ clone) with a whole bunch of TTL cards:

+5V Rail.JPG

There is a reason back in the day many people bought 3rd party upgraded power supplies.  And fans, etc.  If you had all the slots full and several of them were power hungry cards you needed those upgrades.

Not to mention adding an external venting system like Kensington.

Wawavoun wrote:

Hi all,

I experience crash and hangout with this computer when I use Z80 board. They come always during floppy read-write...

The current on the 5 V rail is ~2.4 A without floppy works.

Is it possible that this increase during floppy  r/w operations over the limit and then crash the computer ?

Regards.

Philippe

Hi,

My Apple II is loaded with:

Slot 0  128k Saturn Ram card

Slot 2 1MB Apple Ram card

Slot 3 80 Column Card

Slot 4 Microsoft Softcard II (6mhz one)

Slot 5 The Mill 6809 card

Slot 6 Disk II card

I have my PSU recapped and a small fan internal to the apple ii case to cool electronics and I don't experience any glitch at all..

Luca

It is a good practice to remove cards that you are not presently using.

The power supply will thank you and the computer will probaby run better.

For instance, if you have a serial card in slot 2 and a parallel card in slot 1 and you are running CP/M via a Z-80 card in slot 4, remove the serial card, since you probably won't need it for most CP/M work unless you're using a terminal program.

Besides, you already have a slot-0 RAM card, a slot-6 drive controller, and if you want to run CP/M properly you'll have an 80 column card in slot 3.  That's a lot of cards.

Wawavoun wrote:

I am far from Boletus so loaded configuration ! I have Chat Mauve Eve, Softcard 6 MHz, Super Serial and floppy interface and soon will added diy FPU board.

It is possible that my power supply has never been recaped and that it works well at low power level but not so well at higher one.For sure in the final configuration I think I will overload the psu

Its not very practical to remove  and replace boards because I made a lot of tests and experiments with his Apple IIe.

I will do a test with another power supply with the good voltages and also a lot of more power... Will see !

Thanks for all your advices.Philippe

Recapping your power supply will do nothing for improving its ability to supply current.  It might even make it worse if you don't do a good job and don't specify good parts.

Overdrawing current on the power supply with too many cards will cause a lot of issues, though - voltage sag, primarily, but also a lot of heat.

If you are using your Apple II for "lots of tests and experiments" as you say, then my advice to you would be to use it with the lid removed, and take out cards you are not actively "testing" and "experimenting".

baldrick wrote:

Recapping your power supply will do nothing for improving its ability to supply current.  It might even make it worse if you don't do a good job and don't specify good parts.

 

I completely disagree. The fact that it only glitches during a higher current draw on the +12V rail while the floppy is reading/writing points exactly to a bad capacitor in the PSU or on the motherboard. Besides he doesn't have that many cards plugged in to warrant insufficient power and the PSU should be able to supply 2.4 A to the +5V rail all day long.

Here is the +5V rail current consumption for most of the cards in my collection:

Apple IIe PAL version with all slots empty: 1.08 A

---------------------------------------------------------

CFFA3000 Card + MicroSD Adapter + USB drive: 500 mA

Apple Mouse Interface Card + Mouse: 280 mA

Apple Disk ][ Interface Card + Floppy: 260 mA (doesn't matter if the floppy is reading/writing or not)

Z80 Card (clone): 250 mA

Taxan RGB II Card: 250 mA

ESP32 SoftCard: 190 mA

Printer Interface Card: 150 mA

Apple 64K AUX memory/80 col card: 120 mA

ProDOS ROM-Drive Card: 50 mA

MultiROM card: 30 mA

Dan ][ Controller: 10 mA

Here is the +12V rail consumtion of the Apple Disk ][ Interface Card:

Apple Disk ][ Interface Card with the floppy at rest: 0 mA

Apple Disk ][ Interface Card while the floppy is loading: 680 mA

One thing to check is the voltage of the +12V rail while the floppy is loading something. Here is a video of how it should appear: https://youtu.be/3YKKY5gfDac