Apple II Memory Expansion Card problem

If it's installed in slot 4, then  CALL 50186  will run the built-in diagnostic.

Or, from the monitor use the command: C40AG

The Apple II Memory Expansion Card uses an odd way of ram chip layout. Are yo sure the chips are installed in the right places

I believe that is the correct IC layout for  256k RAM. 

John L wrote:

Ok, when I run that call I get - CARD FAILED   DATA ERROR.

 

So the card is useless now ?

 

Inconclusive from that result, but it's possible.

The test results were designed to help a service technician to identify a specific faulty RAM chip by printing the hexadecimal address where a bit mismatch was detected.

capture273.png

A technician could use that address and byte to identify a specific RAM chip from a table like the one below.  Choose a column based on the address in the error message, and a row based on the hexadecimal byte at the end of the error message.  Each box specifies the coordinate of one specific RAM chip.

EDIT: If this table is unintelligible, scroll to the bottom of this comment for a screencap of a readable version of the table.

first 256K

000000--03FFFF

second 256K

040000--07FFFF

third 256K

080000--0BFFFF

fourth 256K

0C0000--0FFFFF

Unfortunately, that procedure only works if the problem is confined to a faulty RAM chip.

Other components can fail:

• VLSI controller, part 344-0601, is responsible for port IO, address multiplexing, and RAM refresh.
• Bus transceiver, 74HCT245, transfers entire bytes in and out of the memory card.
• 2732 ROM, part 342-0344-A, contains the card's ProDOS driver, DOS 3.3 bootstrap, and SmartPort firmware.

Try running the diagnostic test several times, and look up the result in the table above.  If it consistently gives the same coordinates, like "A12", then it's probably a faulty RAM chip at that location.  But if it gives inconsistent coordinates, like "C4" followed by "A16" followed by "C8", then it's probably a fault elsewhere...and it's not going to be trivial to diagnose.

---------------- EDIT -----------------

Bizarrely, the table is not being displayed properly after I clicked Save.  So here's a screen capture of the table, as it appears in the editor...

RAM card table.png

For comparison, I've been troubleshooting a secondhand Apple II Memory Expansion Card that exhibits similar problems.  At first I suspected a faulty HCT245 transceiver -- a common source of trouble in interface cards. 

But then a pattern emerged in the failure addresses: errors always occur near the start of a logical "sector" address.  In other words, the last two digits were usually 00 or 01 or 02.  (Except for one that ends 0B)

Examples:

DATA ERROR 005E02 - 10

DATA ERROR 008000 - 08

DATA ERROR 001001 - 10

DATA ERROR 001100 - 01

DATA ERROR 00110B - 80

DATA ERROR 001E02 - 40

DATA ERROR 000F00 - 01

These errors typically arise after multiple passes through the entire memory range, which suggests it's not a faulty HCT245 --the transceiver isn't affected by the address, so transceiver faults wouldn't cluster around addresses ending in 00~02 like that.  More likely, it indicates a problem in my card's VLSI controller chip.

John L wrote:

Apple thoughtfully put the VLSI chip in a socket so maybe they anticipated problems with this card ?

...

Not the main reason in this particular case. Without the socket this VLSI chip would require SMD soldering. The socket allows for through-hole.

CVT wrote:

Not the main reason in this particular case. Without the socket this VLSI chip would require SMD soldering. The socket allows for through-hole.

But because it's socketed there's a possibility that some chips might show up in the salvage/recycle ecosystem, like those salvaged KR9600 chips that turned up on AliExpress.  Perhaps not very likely, but possible at least.

My own card appears to be hopelessly faulty: the card's DRAM spontaneously reverts to its "cold start" state, which suggests the controller isn't refreshing properly.   But it's comforting that it fails so explicitly!

Here's one exercise that showed how badly this card is performing...

I used the monitor to store a four-byte test pattern in the card's memory: 66 99 66 99

Then I used the monitor to read it back, and it already had 1 bit error: 66 89 66 99

capture290.png

After letting it 'soak' for 10 minutes, 3 more bits had changed:

capture291.png

I didn't save screencaps, but over the next few hours the DRAM gradually reverted to the data it has at startup, a repeating pattern of 00 00 FF FF.

Memory shouldn't spontanously change like that.  No doubt the card is failing to refresh the DRAM.

S.Elliott wrote:

CVT wrote:

Not the main reason in this particular case. Without the socket this VLSI chip would require SMD soldering. The socket allows for through-hole.

But because it's socketed there's a possibility that some chips might show up in the salvage/recycle ecosystem,

 

This is not a generic chip, I'm afraid. That ⒸAPPLE85 if a huge red flag even for people who gather and sell e-scrap. This makes it a lot closer to the IOU and MMU chips than the keyboard controller.

CVT wrote:

This is not a generic chip, I'm afraid. That ⒸAPPLE85 if a huge red flag even for people who gather and sell e-scrap. This makes it a lot closer to the IOU and MMU chips than the keyboard controller.

Is "generic" a deciding factor to people who gather and sell e-scrap?

That doesn't seem to be the case at ArcadeComponents.com, a medium-volume salvage reseller whose  Custom ROMs and Logic regularly includes both plentiful and rare Apple, Atari, NAMCO, and even TI99/4 custom parts.  (Texas Instruments was notoriously proprietorial about their TI99/4 and its components.)

Consider some examples:

• Apple //e character ROMs are described as "Apple //e" parts, not as generic character generator ROMs.  The plentiful "original" character ROMs cost the same as the scarcer "enhanced" character ROMs.
• Prices appear to be influenced most by the cost of extracting, acquiring, and handling them.  Soldered parts cost more than socketed ones.  Larger DIP packages cost more than smaller ones.
• Scarcity is a factor, but not as much as I would have expected: an IWM costs more than an MMU, yet an IOU costs no more than a Disk II controller ROM.

They don't list the controller for the Memory Expansion Card, but I doubt it's because anyone thought "ⒸAPPLE85" was a red flag.  More likely it's just too obscure to establish an economical salvage channel for itself.

To be fair, the memory card controller lacks a generic identifier -- so a scrapper probably wouldn't know what to call it.  So I concede that a "generic chip" might have been more salvageable...just by having a coherent part number!

PS: Just for reference, the Memory Expansion Card controller (include the //c memory card) always seems to labeled with Apple part number 344-0601, as well as a second part number 7212-0616.

I don't think any of ArcadeComponents.com's chips listed under Custom ROMs and Logic come from e-scrap. Their inventory comes mostly from old new stock, spare parts, or retro devices that have been sold for parts/repair. I would be surprised if any Apple IIs or peripherals for them have gone for scrap in the last 25 years.

What I am referring to is shops like this one, which is where our KR9600-PRO chips from AliExpress most likely came from. They concentrate on chips that are rare/out of production, but also generic enough to have very wide use, so they have a shot at selling them. If an Apple II expansion card was unlucky to ever end up in a place like this (which it won't, considering how few were made), I am pretty sure they would not bother taking the Apple copyright VLSI chip out if its socket and listing it for sale. The reason is simple - if it has copyright, it's either a custom chip or an OTP ROM, which means it can only be used in one device, so its potential for resale is very small.

I can also recommended this awesome video about the fake chip industry, under which the e-scrap chip industry is considered a sub-branch. I find it rather entertaining how as retro-computer enthusiasts we are benefitting from an industry that is otherwise very damaging. :)