English Amiga Board Amiga Lore


Go Back   English Amiga Board > Support > support.Hardware

 
 
Thread Tools
Old 15 July 2017, 00:46   #1
VresiBerba
Registered User
 
Join Date: Dec 2009
Location: Sweden
Posts: 60
Help identifying ROM mod

What is this mod?


Last edited by VresiBerba; 15 July 2017 at 00:51.
VresiBerba is offline  
AdSense AdSense  
Old 15 July 2017, 01:13   #2
Daedalus
Registered User

Daedalus's Avatar
 
Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 2,049
It swaps A12 and the +5V lines. It must be something funky about those particular ROMs or that particular board - no A1200 revision I've ever seen had that mod. It's also got a layer of extra ROM sockets below them that's not normally there - I wonder if it's anything to do with them?
Daedalus is offline  
Old 15 July 2017, 01:18   #3
VresiBerba
Registered User
 
Join Date: Dec 2009
Location: Sweden
Posts: 60
Quote:
Originally Posted by Daedalus View Post
It swaps A12 and the +5V lines. It must be something funky about those particular ROMs or that particular board - no A1200 revision I've ever seen had that mod.
The board revision is 2B.

Quote:
Originally Posted by Daedalus View Post
It's also got a layer of extra ROM sockets below them that's not normally there - I wonder if it's anything to do with them?
It's likely just to preserve the socket since it's an invasive mod.
VresiBerba is offline  
Old 15 July 2017, 20:22   #4
Daedalus
Registered User

Daedalus's Avatar
 
Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 2,049
Yep, I've seen plenty of 2B boards and none with this mod. Good point about the sockets I guess - perhaps the ROMs were the wrong type and were fitted with those sockets at the factory/dealer to make them compatible with the standard ones, but it's a strange one given that they're original mask ROMs.
Daedalus is offline  
Old 16 July 2017, 09:47   #5
RedskullDC
Digital Corruption
RedskullDC's Avatar
 
Join Date: Jan 2007
Location: Sydney/Australia
Age: 53
Posts: 308
Quote:
Originally Posted by Daedalus View Post
It swaps A12 and the +5V lines.
Referring to the datasheet for the MX23C2100 mask rom:
http://pdf1.alldatasheet.com/datashe...MX23C2100.html

It is swapping pins 38 and 32, which are signals A10 and A16.

Perhaps these chips are from a batch of mask roms that were programmed incorrectly?

Cheers,
Red
RedskullDC is offline  
Old 16 July 2017, 18:50   #6
Daedalus
Registered User

Daedalus's Avatar
 
Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 2,049
Sorry - I miscounted, it's A12 and A18 that are swapped. I was speaking from the Amiga's perspective though - it (ab)uses the ROM addressing slightly differently to what you might expect by skipping two address lines. Anyway, I still have never seen such a setup other than on early A500s.
Daedalus is offline  
Old 16 July 2017, 19:09   #7
Sinphaltimus
Registered User

Sinphaltimus's Avatar
 
Join Date: Aug 2016
Location: Cresco, PA, USA
Age: 47
Posts: 625
This is strange - My A500 Rev 5 has a 3.1 rom and it only has one trace wire.

Looking at my mainboard where keyboard = south and rear end = north, I have a wire going from the northern most left side of chip opin into a socket pin port on the right side of the chip a few pins down. I looked up A500 rom mods and they all seem to require 2 traces. So I'm not sure how this was modded before I got it but it works.

Can anyone explain?
Sinphaltimus is offline  
Old 17 July 2017, 07:10   #8
Jope
-
Jope's Avatar
 
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 37
Posts: 6,220
Send a message via Skype™ to Jope
If it is a 3.1 mask ROM, then just the address line swap is needed, no bent pins + no second jumper. If it is an EPROM, then the 16bit mode jumper is needed, one pin is bent up and grounded.
Jope is offline  
Old 17 July 2017, 12:34   #9
FOL
PSPUAE DEV

FOL's Avatar
 
Join Date: Nov 2006
Location: Barry / UK
Age: 39
Posts: 5,525
Send a message via MSN to FOL Send a message via Skype™ to FOL
Ive seen lots of these. On different rev boards.
I have even seen them on CD32. So I would go with mis-programmed batch of chips theory.
FOL is offline  
Old 17 July 2017, 13:18   #10
VresiBerba
Registered User
 
Join Date: Dec 2009
Location: Sweden
Posts: 60
Quote:
Originally Posted by FOL View Post
Ive seen lots of these. On different rev boards.
I have even seen them on CD32. So I would go with mis-programmed batch of chips theory.
So factory mod, then?
VresiBerba is offline  
Old 17 July 2017, 13:53   #11
Jope
-
Jope's Avatar
 
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 37
Posts: 6,220
Send a message via Skype™ to Jope
Quote:
Originally Posted by VresiBerba View Post
So factory mod, then?
Yep, the one in your picture is a factory mod.
Jope is offline  
Old 17 July 2017, 14:07   #12
Sinphaltimus
Registered User

Sinphaltimus's Avatar
 
Join Date: Aug 2016
Location: Cresco, PA, USA
Age: 47
Posts: 625
I'm certainly not trying to hyjack this thread but it seems more logical to keep similar questions here rather than spark a bunch of topics around the same subject.

Here's the single wire mod on my A500 Rev5. I'm guessing there was another modifications made for this on the mainboard someplace.b Possibly that JP2 mod. Not sure if that was for the chip ram Mod or not.
Attached Thumbnails
Click image for larger version

Name:	20170711_180034.jpg
Views:	65
Size:	559.1 KB
ID:	53761   Click image for larger version

Name:	20170711_180047.jpg
Views:	51
Size:	562.9 KB
ID:	53762   Click image for larger version

Name:	20170717_075900.jpg
Views:	44
Size:	591.5 KB
ID:	53763  
Sinphaltimus is offline  
Old 17 July 2017, 14:34   #13
Jope
-
Jope's Avatar
 
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 37
Posts: 6,220
Send a message via Skype™ to Jope
In your case, the second wire is the grey conductive paint.

Even though it seems like a novel approach at first, I think this might be the result of mistakenly breaking off the pin while bending it. ;-)
Jope is offline  
Old 17 July 2017, 14:40   #14
VresiBerba
Registered User
 
Join Date: Dec 2009
Location: Sweden
Posts: 60
Quote:
Originally Posted by Jope View Post
Yep, the one in your picture is a factory mod.
Cool, thanks
VresiBerba is offline  
Old 17 July 2017, 15:25   #15
Sinphaltimus
Registered User

Sinphaltimus's Avatar
 
Join Date: Aug 2016
Location: Cresco, PA, USA
Age: 47
Posts: 625
Quote:
Originally Posted by Jope View Post
In your case, the second wire is the grey conductive paint.

Even though it seems like a novel approach at first, I think this might be the result of mistakenly breaking off the pin while bending it. ;-)

OH, I hadn't noticed that - I honestly thought it was wear and tear of the chip being mishandled at some point. Thanks for the answer! Makes sense now. I could probably repair that and do a better job with the existing wire. But right now I'll stand by "if it ain't broke don't fix it".
Sinphaltimus is offline  
Old 17 July 2017, 17:54   #16
Akira
Registered User

Akira's Avatar
 
Join Date: May 2001
Location: New York
Posts: 17,672
Quote:
Originally Posted by Sinphaltimus View Post
IHere's the single wire mod on my A500 Rev5. I'm guessing there was another modifications made for this on the mainboard someplace.b Possibly that JP2 mod. Not sure if that was for the chip ram Mod or not.
I had this same mod on my rev5 and also asked about it before:
http://eab.abime.net/showthread.php?t=83728
Akira is offline  
Old 01 August 2017, 15:50   #17
RedskullDC
Digital Corruption
RedskullDC's Avatar
 
Join Date: Jan 2007
Location: Sydney/Australia
Age: 53
Posts: 308
An A1200 motherboard currently on Ebay:
http://www.ebay.com.au/itm/192263972958

Has the same "MX" chips, same wire mods. (Same colour green even!).

Cheers,
Red
RedskullDC is offline  
Old 01 August 2017, 23:54   #18
idrougge
Registered User
 
Join Date: Sep 2007
Location: Stockholm
Posts: 2,976
I've seen those wires on MX ROMs before, but I can't remember if they were cut off or not.
idrougge is offline  
AdSense AdSense  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Help me Identifying this please. Thalion Hardware pics 6 26 March 2016 16:32
A1000 Kickstart ROM Mod xArtx Hardware mods 0 23 January 2016 04:41
A3000/4000 1MB ROM Mod SpeedGeek Hardware mods 1 05 November 2014 16:03
Identifying a mod Eamoe support.Hardware 2 02 May 2011 12:23
Help identifying a battery Antti support.Hardware 3 27 January 2010 12:21

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 04:53.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Page generated in 0.33013 seconds with 15 queries