5101 CMOS RAM Compatability

[Mattrock1]

Anyone know the answer?

I have a board with a Motorola MCM145101-3P memory in it. It is a
256x4 static ram.
I tried to replace it with a phillips PCD5101P memory from Great
Plains. It is also a 256x4 static Ram in the same package. It didnt
work. Anyone know why this wouldnt replace it? It has been
suggested it is a speed difference. Any truth to that?

Thanks

Matt

[Dan Beck]

Hopefully Ed wil chime in here, but...

Yes, there are speed differences with a given 5101 chip; it may be encoded
in the p/n of the chip. What kind of board are you trying to swap the 5101
in?

Regards,
Dan

Post by Mattrock1
Anyone know the answer?
I have a board with a Motorola MCM145101-3P memory in it. It is a
256x4 static ram.
I tried to replace it with a phillips PCD5101P memory from Great
Plains. It is also a 256x4 static Ram in the same package. It didnt
work. Anyone know why this wouldnt replace it? It has been
suggested it is a speed difference. Any truth to that?
Thanks
Matt

[GPE]

Post by Mattrock1
Anyone know the answer?
I have a board with a Motorola MCM145101-3P memory in it. It is a
256x4 static ram.
I tried to replace it with a phillips PCD5101P memory from Great
Plains. It is also a 256x4 static Ram in the same package. It didnt
work. Anyone know why this wouldnt replace it? It has been
suggested it is a speed difference. Any truth to that?
Thanks
Matt

The Philips PCD5101P's are pretty quick when ran at +5V -- they have a
random access time of 150nS. So I doubt access time is the problem.

I can find absolutely nothing on the Motorola MCM145101-3P's. As a wild
guess on the part number - I would assume these to be 300nS parts.
Normally, running faster parts doesn't cause a problem...except in very poor
designs.

All 5101's have CMOS (low power) cores. Some 5101's have TTL level
interface pins (i.e. PCD5101's) and some have CMOS level interface pins
(i.e. some RCA devices). Not sure about the Motorola part's Interface pins.
It might be possible they are CMOS only. In fact - a new PCD5101 not
working in this board - I would highly suspect this reason. I'm not
familiar with 1979 Seeburg Jukebox's - they might be expecting the 5101 to
have CMOS I/O pins. Are there schematics online somewhere to look at?

There is also a variant with registered I/O pins (or what it registerd
control lines? can't remember). Could be that the MCM145101 falls into that
category. This part is more commonly known as the 74C920.

Or.... possibly the 5101 is not the problem but resides in the problem area
of the board (electronically wise)?

-- Ed

[Mattrock1]

Ed, thank you for the detailed reply. I had purchased a few Philips
5101's from you a while back for use on Bally pinball CPU's. So when
I ran across this Motorola 5101 from 1979, I figured it would work
(the spec sheet says it is a fairly slow 650ns part). From what I
could gather, anything faster than 650ns then would work. So, I
slapped it in and it was just haywire.
That's when I went on the witch hunt and emailed you, not knowing what
to do next. I also emailed a guy named Tony Dziedzic who works on
Seeburg jukes. He replied that the Philips part should work ... and if
it didn't, are you sure it is good? ( he explained they are very
static sensitive)
So, since I had another, I popped it in using the latest voodoo static
techniques I could google up ... and Voila! It worked. It had been
stored in the antistatic bag it was shipped in. I must have handled it
wrong on the install.
So thanks again for the good info, and sorry for wasting your time!

Matt

PS. If your reading this post, www.greatplainselectronics.com is a
great source for hard to find electronic parts for video, pinball and
early modern stuff. And Ed is a great guy too!

[Steve Kulpa]

Shoot Ed at GPE an e-mail. He'd know. or just wait for his reply on
this topic. He'll chime in soon, I'm sure

steve
---
Steve Kulpa (cargpb10)
Hermitage, TN
http://www.geocities.com/stevekulpa/faces/rgpidx.htm - Faces
http://www.geocities.com/stevekulpa/pinball.htm - Pinball

[Steve Kulpa]

I forgot to mention - those devices are very sensitive to static, so
slight that you don't even see or feel it. Are you sure you handled
it properly?

steve (again)
---
Steve Kulpa (cargpb10)
Hermitage, TN
http://www.geocities.com/stevekulpa/faces/rgpidx.htm - Faces
http://www.geocities.com/stevekulpa/pinball.htm - Pinball