View Full Version : Found HM4816 RAM Chips for Acorn BBC

30th August 2011, 12:44
Hello my friends...

Looking to refurb an Acorn BBC Micro Model B for our resident Wizard.

I need to source some RAM chips of the 4816AP-3 variety

and some 74LS245N IC's too.

If anyone can help in any way it would be much appreciated

TC :thumbsup:

30th August 2011, 13:24

my friend, I may have some LS245's and I have a slew of 16pin DIP KM4164B-10 (64k*1) memories.

I couldn't find any spec sheet for the 4816AP-3 =(

anyway the above are yours if you can make use of 'em =)

30th August 2011, 13:54
Datasheet HITACHI HM4816 (http://dl.free.fr/kAZxDAA4z)

30th August 2011, 14:11
Datasheet HITACHI HM4816 (http://dl.free.fr/kAZxDAA4z) :thumbsup::thumbsup:


My friend, these 4164's look like drop in replacments... they look pin conpatible!

http://s2.postimage.org/4rrboce9y/lookie.jpg (http://www.postimage.org/)

just let me know how many you want =)

30th August 2011, 23:58
Hmm Now that's interesting, thanks for that Zeets :thumbsup:

I've got a couple of 4164's here from when I upgraded my TRS-80 CoCoII to 64K (swapped them for 4464's)

I will give it a go by holding the A7 pin down to gnd & see if they can cope with the 4MHz DRAM refresh clock that the Beeb uses.

If it works I could certainly do with a dozen or so as I have another board here with a RAM fault (fatbob_gb) I just haven't been able to get hold of the HM4816's easily to fix it..
Refurbing this one for you has given me the push to get them both going..

Interesting & Cheers Chap

TC ;)

31st August 2011, 00:53
Thats awsome buddy!

I have 36 of them... infact I am not sure how I got them.... freaky... anyway I am still waiting on some bits for your parcel so I shall send half of what I have out to you if there any good =)

the ones I have here are the -10 (100ns) varients... which are pretty damn quick for most applications... should be able to cope with a 4MHz bus =)

31st August 2011, 09:20
Cheers Zeets

I've posted over at Stairway to Hell forums to see what the techy guys over there make of it too..


The guy's over there are very knowledgeable too will be nice to see what they have to say

Cheers again
TC :thumbsup:

31st August 2011, 19:49

The 4164's I have are 18Pin not 16Pin

Everywhere I look at datasheets I find 16Pin versions of the 4164, god knows what mine actually are, as I mentioned earlier these were taken from my CoCo & they are marked 4164 ????. The 4464 is also 18Pin which is what i used to replace the originals with.

Wierd :lol:

On a lighter note I have traced the fault on one of the boards to a single DRAM in the CAS1 bank, quick desolder, fitting a socket & borrowing a DRAM from one of my working Model B's proved I was correct.
So if I can get hold of a replacement DRAM that's another Model B Beeb fully repaired & back in the land of the living.

TC :whistle:

31st August 2011, 20:40

my friend, the ones i have here are 16pin (DIP )

I have just counted them three times LOL... there certainly 16pin like the schematics above that I got online... one from LTAC's link the other from all DataSheets...

I am sure there might be a specific 18PIN dip varient... but these little puppies are indeed 16pin KM4164B-10

I think I got this cache I have here from fleabay, problem is I cannot remember what they were listed as... If memory serves (forgive the pun) these were from a joblot a few years back that was into 8bit computer repairs... I got a bunch of 27c32's 64's and 128's aswell as some new resistors / caps and some common TTL IC's....

Thinking about it.... I may of got these before AmiBay was aroud..... t'is'was a while back my friend..... =)

Anyway I got the following in a box

36x KM4164B-10 (64k * 1 bit ) - 16 PIN DIP (Samsung)
18x M5M4256-AP (256k * 1 bit ) - 16 PIN DIP (Mitsubishi)
15x M514256A -70 (256k * 4bit ) - 20 PIN DIP (OKI)

now the OKI's are spoken for... but your welcome to half the others for grattis =D

31st August 2011, 20:46
Cheers Mate

If I can take 16 of the KM4164B-10 (64k * 1 bit ) - 16 PIN DIP (Samsung)
off your hands that would be great.
I may have to replace all the DRAMS in the bank to the same type if it works hence the qty required ;)

Having checked the Beeb's PCB Pin 9 (A7) is not connected to anything either.

Thanks indeedy

TC :thumbsup:

31st August 2011, 21:01
my pleasure my friend.... instead of waiting for the parcel I am sending these will go in a jiffy bag tonight =)

hit me up with your deets please =D

13th September 2011, 00:20
Just to update the thread

The KM4164B-10 DRAMS that Zeets sent function perfectly and are straight drop in replacements.

I replaced just the defective DRAM & the KM4164 seemed quite happy sharing the Bus with the HM4816's

Sorted :thumbsup:

13th September 2011, 01:29
Just to update the thread

The KM4164B-10 DRAMS that Zeets sent function perfectly and are straight drop in replacements.

I replaced just the defective DRAM & the KM4164 seemed quite happy sharing the Bus with the HM4816's

Sorted :thumbsup:

AWESOME! :thumbsup::thumbsup::thumbsup::thumbsup:

13th September 2011, 01:42