HiI received a non-working Disk II Interface Card - I assume, the disk's ribbon cable was connected incorrectly… I compared the card to a working one by measuring the expected signals and swapping chips. A total of 3 ICs failed --> C3 (74LS323), B2 (74LS05) and B3 (PROM P6).
The two TTL logic IC's were easily replaced with spare parts I found. The real problem lies in P6. By replacing it with another P6 from a working card, I verified, that the interface card is working. Some research led me to the AMD AM27S23APC PROM, which is avaylable on E-Bay. But… I don't have a programmer to write the Code into the PROM.
So I'm looking for:
- a) a spare P6 (16 Sector Programmed)
- b) an alternative for the AM27S23APC - which could preferably be programmed with the TL866II plus
- c) a way to programm the AM27S23APC
Any answer to any of these 3 questions would be extremly helpful.
Cheers Peter
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Disk%20Drive%20Controllers/Apple%20Disk%20II%20Interface%20Card/ROM%20Images/
Also check with Reactive Micro, not sure if they could program for you but worth a shot.
BiPolar PROMs like the ones used for the P5 and P6 PROM on a Disk ][ Controller Card are nearly ubobtanium these days. If you can find any, they are usually expensive. There are few programmers out there anymore that can handle them either. The TL866-II definitely will not. Even the older TL866CS will not, even though it can do a lot of older chips that the -II version can't. I don't know of any modern programmer that can handle the BiPolar PROMs other than perhaps some high end pro ones that are out of the realm of affordability. And the old ones are hard to find, expensive if you can... and often need to be hooked up themselves to a vintage computer to be used.
There have been a few homebrew projects over the years to program these chips, but a lot of them suffer from the same issues as the vintage commercial ones -- the hardware and software is designed for use with old PCs that still had things like DB-25 parallel ports, etc...
The way I got one to fix a bad Disk ][ Controller card I had was to take one off an Apple 5.25 Controller Card (the one with the single DB19 connector) that someone had ruined by yanking the (soldered on) cable off the board.
TPB28L22 was also used on the Disk Controller PROM but that's even harder to find.
You probably could do it with a 2716, but it would be ugly.
Some clone disk controller cards (like Franklin) used a 2716 (2kx8) EPROM instead of two 256x8 BiPolar PROMs. The 2716 has twice the needed space so they usually had a switchable 13/16 sector boot option. There were also aftermarket little daughter boards which had a 2716 and two DIP jumpers that went to the PROM sockets and a usually externally accessable switch to select between 13/16 sector boot. That kind of mod could be re-created to rescue Apple style controller cards without needing unobtanium BiPolar PROMs. It doesn't have to be all that ugly if done right.
This is an example from my collection. You can see the missing S1 which is used to select 13-16 sector boot. You can infer that the circuit of this card and the circuit of a genuine Disk-II is pretty much identical (with necessary pin re-routing for the 2716s) from the chip selection.
Disk II 2716.jpg
By a peculiar conincidence, this item came through just now on my daily eBay email feed, which is exactly what you were talking about.
https://www.ebay.com/itm/115256760230
Pretty sure this can be done using a surface-mount 16 bit flash eeprom on a tiny board that can plug into the Disk II intervace card's PROM sockets in that same fashion.
Yes, a gigantic waste of eeprom memory, but a huge money saver. Can be made on the cheap. One small chip does it all, and in a tiny space as well.
An MX29F1610MC chip comes to mind but there are others that can do the job too. Haven't considered the chip dimensions. Just thinking out loud...
Hello,
I'm not sure if it will be an issue, especially with protected disks, but the flash memory MX29F1610MC (120nS) has more than twice the access time compared to the TBP28L22N prom (50nS).
The" Woz" disk controller is fully controlled by software.
EEPROM type 2716 are even much slower.
Just my 2 cents.
Yves
In post #9, 'YLG80' wrote:
" I'm not sure if it will be an issue, especially with protected disks, but the flash memory MX29F1610MC (120nS) has more than twice the access time compared to the TBP28L22N prom (50nS)."
Uncle Bernie comments:
Somewhere on Applefritter (but in another thread) I've shown the calculations for the required access time of any memory IC that replaces the PROM in the Woz Machine, but at the moment I'm in a hurry and can't try to find it - you try !
I think that 120ns is fast enough but as I can't find my original post with the calculations, I'm not sure.
To avoid the colossal waste of memory, you can use a 22V10 PAL or GAL instead. I have tested this on a real DISK II card and it works fine. With a little mod, you can also make a 22V10 which can control a 74LS299 in lieu of the harder to find / more expensive 74LS323. The same equations from the 22V10 also were used in my 'IWMless'.
Be aware that there are some 22V10 JEDECs out there for the same purpose, but these were made by third parties and so I can't vouch for them. The mine I did not publish so far.
- Uncle Bernie