Computer memory - UK Vintage Radio Repair and Restoration Discussion Forum

G6ONEDave · 11th Oct 2022, 12:21 pm

Hi, I'm trying to confirm the number of Mb's on a couple of Dram cards containing the following chips and hope that a forum member can assist.

The first one is Siemans HY8511000BJ-70, I think this might be a 1Mb.

The second is NEC 421000-70 and the module has MC-421000A9B-8C printed on it. Don't know idf this is 1Mb or possibly 4Mb.

Both these Dram modules haveare 9 chips fitted.

Thanks

Dave

SiriusHardware · 11th Oct 2022, 1:15 pm

For your first one try searching Siemens HYB511000BJ

Data sheet here says they are 1M by 1 bit.

https://html.alldatasheet.com/html-p...1000BJ-70.html

SiriusHardware · 11th Oct 2022, 1:32 pm

For the second, this page which lists some MC-421000A9A (not B) for sale (check the price!) says they are 1M by 1 bit, although they are being offered as a 4MB set. unfortunately I don't know the significance of A versus B suffix in this case.

https://classiccomputershop.eu/Webwi...retro-80s.html

Regarding the capacity, a module with nine of these 1 Megabit chips on it will be 1 Megabyte (8 bits wide) with the ninth chip / bit being for parity.

G6ONEDave · 11th Oct 2022, 1:38 pm

Thanks Sirius, that will teach me to use a magnifier when looking at chip numbers. I did find that classiccomputershop site but I was confused that they had both 1Mb and 4Mb showing for the same module. I suspect that I'm not going to be lucky enough to have 8 MC-421000A9A modules at 4Mb but you never know. Personally I think that the '1000' part of the number infers 1Mb as it seems to do with other modules that I've checked. I just thought that members such as your good self would be able to confirm one way or the other.

Dave

G6ONEDave · 11th Oct 2022, 1:45 pm

Oh, I should have mentioned that I'm looking for Drams suitable for an IBM Opal 486SLC2 mobo and the mobo does take up to 4 of the 4M x 9 Dram modules according to the user manual. This is in relation to being able to find out what is on the spool tapes with the Kennedy 9610 tape deck in case you had not twigged. I'm quite a way of from getting this all sorted but am trying to source anything that will help.

Dave

G6ONEDave · 11th Oct 2022, 4:10 pm

I've now identified the mystery NEC SIMM, it would appear that the 421000-70 is also a 1Mb type as on a German RAM suppliers web page they have an NEC 424100-70 listed as 4Mb.

This thread can now be closed.

Dave

11th Oct 2022, 12:21 pm	#1
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,704	Computer memory Hi, I'm trying to confirm the number of Mb's on a couple of Dram cards containing the following chips and hope that a forum member can assist. The first one is Siemans HY8511000BJ-70, I think this might be a 1Mb. The second is NEC 421000-70 and the module has MC-421000A9B-8C printed on it. Don't know idf this is 1Mb or possibly 4Mb. Both these Dram modules haveare 9 chips fitted. Thanks Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

11th Oct 2022, 1:15 pm	#2
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,583	Re: computer memory For your first one try searching Siemens HYB511000BJ Data sheet here says they are 1M by 1 bit. https://html.alldatasheet.com/html-p...1000BJ-70.html

11th Oct 2022, 1:32 pm	#3
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,583	Re: computer memory For the second, this page which lists some MC-421000A9A (not B) for sale (check the price!) says they are 1M by 1 bit, although they are being offered as a 4MB set. unfortunately I don't know the significance of A versus B suffix in this case. https://classiccomputershop.eu/Webwi...retro-80s.html Regarding the capacity, a module with nine of these 1 Megabit chips on it will be 1 Megabyte (8 bits wide) with the ninth chip / bit being for parity.

11th Oct 2022, 1:38 pm	#4
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,704	Re: computer memory Thanks Sirius, that will teach me to use a magnifier when looking at chip numbers. I did find that classiccomputershop site but I was confused that they had both 1Mb and 4Mb showing for the same module. I suspect that I'm not going to be lucky enough to have 8 MC-421000A9A modules at 4Mb but you never know. Personally I think that the '1000' part of the number infers 1Mb as it seems to do with other modules that I've checked. I just thought that members such as your good self would be able to confirm one way or the other. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

11th Oct 2022, 1:45 pm	#5
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,704	Re: computer memory Oh, I should have mentioned that I'm looking for Drams suitable for an IBM Opal 486SLC2 mobo and the mobo does take up to 4 of the 4M x 9 Dram modules according to the user manual. This is in relation to being able to find out what is on the spool tapes with the Kennedy 9610 tape deck in case you had not twigged. I'm quite a way of from getting this all sorted but am trying to source anything that will help. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

11th Oct 2022, 4:10 pm	#6
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,704	Re: computer memory I've now identified the mystery NEC SIMM, it would appear that the 421000-70 is also a 1Mb type as on a German RAM suppliers web page they have an NEC 424100-70 listed as 4Mb. This thread can now be closed. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)