Amiga 2000 RAM questions

Kepler · 09 September 2023, 05:21

Hi all,

My rev 4.1 has thirty two 41256C-15 RAM ICs arranged in four rows of 8. I also have a green/red screen in Diagrom. I know this maybe related to chip RAM. Therefore I am considering removing all 32 ICs and checking each one.

My questions are:

1. What is the minimum amount of RAM required for Diagrom/the Amiga to boot?
2. Where should those ICs be fitted?
3. Could I use TMS4256-15NL/TMS4257-15NL in place of the 41256C?
4. I have a 1MB Commodore RAM expansion which I know works. However, when inserted into the processor socket, Diagrom does not even show the green red flashing screen. Is that normal/expected behavior for a machine in this state?

Kepler · 10 September 2023, 10:15

I received it non working, there was only a blank display. The battery had been removed but there was some damage. I have since:
Replaced the processor socket
Replaced the Agnus socket (as a precaution)
Checked every pin from the 68000 to its destination
Checked every pin on the Agnus to its destination
Checked every pin on the Kickstart IC to its destination
Replaced every custom IC
Fixed after this process several broken traces - all were to the right of the processor.

...and now I am left with a green red screen with Diagrom..which leads me to the next stage: check the RAM, which was the reason for my initial question.

Kepler · 10 September 2023, 17:26

Yes, I have tried that but I receive no output even though according to my logic probe, there is activity on the transmit line from the cable. I therefore suspect my Serial to USB adapter isn't working or I have not configured it correctly in Putty. Although, there isn't actually much to configure other than select the serial Com port. I have seen references to "8N1", where is that to be entered?

nogginthenog · 11 September 2023, 18:35

You probably need a 'null modem' cable. This is where the transmit on one side does to receive on the other and vice versa.
There are adapters or you could re-wire the cable. Search eBay for 'null modem'.

8N1 is just 8 bits, no parity, 1 stop bit. It's the normal setting used pretty much everywhere.

Kepler · 12 September 2023, 11:41

I have a null modem cable which my logic probe tells me is transmitting data. So the fault is with my Serial to USB adapter or the settings in Putty.

09 September 2023, 05:21	#1
Kepler Registered User Join Date: Jun 2023 Location: UK Posts: 55	Amiga 2000 RAM questions Hi all, My rev 4.1 has thirty two 41256C-15 RAM ICs arranged in four rows of 8. I also have a green/red screen in Diagrom. I know this maybe related to chip RAM. Therefore I am considering removing all 32 ICs and checking each one. My questions are: 1. What is the minimum amount of RAM required for Diagrom/the Amiga to boot? 2. Where should those ICs be fitted? 3. Could I use TMS4256-15NL/TMS4257-15NL in place of the 41256C? 4. I have a 1MB Commodore RAM expansion which I know works. However, when inserted into the processor socket, Diagrom does not even show the green red flashing screen. Is that normal/expected behavior for a machine in this state?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Amiga 2000 Accelerator / Ram Upgrade	ourflat	support.Hardware	6	19 December 2022 01:32
Amiga 2000 No Chip Ram Detected	stephenfalken	support.Hardware	0	26 March 2019 09:12
Video Toaster 4000 for Amiga 2000 questions	antiriad76	support.Hardware	3	18 September 2016 17:47
Amiga 2000 RAM issue	Six	support.Hardware	13	04 January 2007 16:55
Amiga 2000 questions	cane	support.Hardware	7	13 January 2005 17:50

10 September 2023, 10:15	#2
Kepler Registered User Join Date: Jun 2023 Location: UK Posts: 55	I received it non working, there was only a blank display. The battery had been removed but there was some damage. I have since: Replaced the processor socket Replaced the Agnus socket (as a precaution) Checked every pin from the 68000 to its destination Checked every pin on the Agnus to its destination Checked every pin on the Kickstart IC to its destination Replaced every custom IC Fixed after this process several broken traces - all were to the right of the processor. ...and now I am left with a green red screen with Diagrom..which leads me to the next stage: check the RAM, which was the reason for my initial question.

10 September 2023, 17:26	#3
Kepler Registered User Join Date: Jun 2023 Location: UK Posts: 55	Yes, I have tried that but I receive no output even though according to my logic probe, there is activity on the transmit line from the cable. I therefore suspect my Serial to USB adapter isn't working or I have not configured it correctly in Putty. Although, there isn't actually much to configure other than select the serial Com port. I have seen references to "8N1", where is that to be entered?

11 September 2023, 18:35	#4
nogginthenog Amigan Join Date: Feb 2012 Location: London Posts: 1,309	You probably need a 'null modem' cable. This is where the transmit on one side does to receive on the other and vice versa. There are adapters or you could re-wire the cable. Search eBay for 'null modem'. 8N1 is just 8 bits, no parity, 1 stop bit. It's the normal setting used pretty much everywhere.

12 September 2023, 11:41	#5
Kepler Registered User Join Date: Jun 2023 Location: UK Posts: 55	I have a null modem cable which my logic probe tells me is transmitting data. So the fault is with my Serial to USB adapter or the settings in Putty.

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