(Topic ID: 264243)

High Speed ROMs won't work in Sys 11a MPU

By FiatsRUs

1 year ago



Topic Stats

  • 9 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by DumbAss
  • Topic is favorited by 1 Pinsider

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#1 1 year ago

I have a project High Speed with a locked MPU. The MPU is NOT an original 11, but is instead an 11a (5764-12091-00). I purchased a new pair of ROMs for U26 and U27 and they test good in a friend's HS with an original Sys 11-nothing MPU. They are burned to a 2764 at U26 and a 27256 at U27, which I believe is the same setup as the original ROMs.

My question: Do I need a pair of 27256 ROMs (both U26 and U27) for them to work in the 11a MPU? I have an 11b MPU from a working Jokerz and the known-to-be-good HS ROMs will NOT boot in it. When I put the working Jokerz ROMs (both 27256) in the locked 11a MPU, it gets closer to booting.

Thoughts?

#2 1 year ago

What's the trusty old manual say they are?

#3 1 year ago
Quoted from FiatsRUs:

They are burned to a 2764 at U26 and a 27256 at U27, which I believe is the same setup as the original ROMs.
My question: Do I need a pair of 27256 ROMs (both U26 and U27) for them to work in the 11a MPU? I have an 11b MPU from a working Jokerz and the known-to-be-good HS ROMs will NOT boot in it. When I put the working Jokerz ROMs (both 27256) in the locked 11a MPU, it gets closer to booting.
Thoughts?

I believe you have two options.

1) Remove W2 and install W3.
2) Double the image and write it to a 27128 (or quadruple the image and write it to a 27256).

#4 1 year ago
Quoted from DumbAss:

I believe you have two options.
1) Remove W2 and install W3.
2) Double the image and write it to a 27128 (or quadruple the image and write it to a 27256).

I did option one to both the 11a board and the known-to-work 11b board. Neither board showed any sign of life with the High Speed ROMs.

On the working 11b board, put the jumper back to W2 and it boots fine with the Jokerz ROMs (both 27256).

#5 1 year ago
Quoted from FiatsRUs:

I purchased a new pair of ROMs for U26 and U27 and they test good in a friend's HS with an original Sys 11-nothing MPU. They are burned to a 2764 at U26 and a 27256 at U27, which I believe is the same setup as the original ROMs.

Check the jumper configuration of that System 11 (nothing) board. If it works and you have a 2764 then it should have W2 out and W3 in.

Quoted from FiatsRUs:

When I put the working Jokerz ROMs (both 27256) in the locked 11a MPU, it gets closer to booting.

This would suggest to me that your System 11A board has an issue that you need to resolve. Get it working first with a System 11A/B EPROM set (27128 or doubled 27256 at U26 and 27256 at U27).

#6 1 year ago
Quoted from DumbAss:

Check the jumper configuration of that System 11 (nothing) board. If it works and you have a 2764 then it should have W2 out and W3 in.

My friend checked his Sys 11-nothing in which my HS ROMs work. It is jumpered at W2, not W3 (see the attached pic).

Quoted from DumbAss:

This would suggest to me that your System 11A board has an issue that you need to resolve. Get it working first with a System 11A/B EPROM set (27128 or doubled 27256 at U26 and 27256 at U27).

Yes the Sys 11A MPU cleary has some issues, but I want to eliminate the ROMs as an issue so I can get it working. It seems that I should be able to use my Jokerz ROMs in it to do the troubleshooting, but I am puzzled as to why I can't get the HS ROMs to work in anything but a Sys 11-nothing MPU. The answer would seem to be jumpers because of the difference in the ROM chip at U26 (U26 and U27, respectively, are 2764 and 27256 for the HS and 27256 and 27256 for the Jokerz).

Once I get the 11A working properly, I need to be able to use it with the HS ROMs to get my project up and running.
19454 (resized).jpeg

#7 1 year ago

I don't have any 2764. I only use 27256 and double or quadruple images to use them. I do have an original System 11 (nothing) board but without the 2764 I cannot verify anything (short of looking at actual traces to verify the schematics match the traces).

If I were in this situation I'd use either a 27128 or 27256 in U26 and get your System 11A board working.

#8 1 year ago
Quoted from DumbAss:

I don't have any 2764. I only use 27256 and double or quadruple images to use them. I do have an original System 11 (nothing) board but without the 2764 I cannot verify anything (short of looking at actual traces to verify the schematics match the traces).
If I were in this situation I'd use either a 27128 or 27256 in U26 and get your System 11A board working.

Pardon my ignorance (I don't burn my own ROMs), but what is it to "double or quadruple images"? I use Matt's Basement Arcades for ROM purchases. Can he burn me just a U26 doing what you described or do I need to purchase another pair for both U26 and U27?

#9 1 year ago
Quoted from FiatsRUs:

Pardon my ignorance (I don't burn my own ROMs), but what is it to "double or quadruple images"? I use Matt's Basement Arcades for ROM purchases. Can he burn me just a U26 doing what you described or do I need to purchase another pair for both U26 and U27?

No need to apologize for not knowing. It's always better to state you don't know something and ask for an explanation than stumble around and string someone along thinking that they think you know.

The section @ https://www.pinwiki.com/wiki/index.php?title=Burning_EPROMS#Using_EPROMS describes doubling an image. Essentially it is an exact (binary) duplication of an image. If you use a service and the person providing the service has interaction then ask the person to write the image onto the specified sized EPROM. Any person providing the service should be able to do this for you (presumably at no additional charge since it is literally executing one or two commands in a console).

Edit: You only need the U26 image doubled to a 27128 or quadrupled to a 27256. U27 is already written to a 27256.

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