16 Nov
1998
16 Nov
'98
9:13 a.m.
On Nov 16, 5:39, Doug Spence wrote:
They're NOT the same. I can't find a pinout, but they're a different
(physical) size and ISTR they use different voltages as well. MPS6550s
will be very hard to find as they were never second-sourced by anyone, as
far as I know. They're 22-pin (0.4" wide instead of 0.3") 4096-bit (1024 x
4) SRAMs. 2114's are 18-pin 4096-bit (1024 x 4) SRAMs.
Even MOS Technology didn't make them for very long, which is why only the
earliest PETs used them.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
On Tue, 10 Nov 1998, Tony Duell wrote:
> The 2114 is getting hard to find now. A few
companies still have them
in
stock, but
AFAIK it's no longer in production.
Ack! I need a bunch of these to get a PET 2001 going (all of the 6550s
are bad, and I was told that the 2114 is the same part?) and a VIC 3K RAM
Expander fixed. 
16 Nov
16 Nov
noon
On Nov 16, 5:39, Doug Spence wrote:
They're NOT the same. I can't find a pinout, but they're a different
(physical) size and ISTR they use different voltages as well. MPS6550s
will be very hard to find as they were never second-sourced by anyone, as
far as I know. They're 22-pin (0.4" wide instead of 0.3") 4096-bit (1024
x
4) SRAMs. 2114's are 18-pin 4096-bit (1024 x 4) SRAMs.
Even MOS Technology didn't make them for very long, which is why only the
earliest PETs used them.
According to the GIICM (http://www.falstaff.demon.co.uk/giicm.html)
2114 - 1kx4 SRAM.
+---+--+---+
A6 |1 +--+ 18| VCC
A5 |2 17| A7
A4 |3 16| A8
A3 |4 15| A9
A0 |5 2114 14| D1
A1 |6 13| D2
A2 |7 12| D3
/CE |8 11| D4
GND |9 10| /WE
+----------+
And adapted from the PET schematics at
http://www.funet.fi/pub/cbm/schematics/computers/pet/2001/320008-2.gif
+---+--+---+
A0 |1 +--+ 22| VSS (GND)
A1 |2 21| CS1
A2 |3 20| CS2
A3 |4 19| /CS3
A4 |5 6550 18| /CS4
A5 |6 17| VDD (+5v)
Ph2 |7 16| D3
A6 |8 15| D2
A7 |9 14| D1
A8 |10 13| D0
A9 |11 12| R/W
+----------+
While the RCA 1822 looked like this...
(Courtesy of http://www.semi.harris.com/data/pk/pk0/pk0069/)
+---+--+---+
A3 |1 +--+ 22| VDD (+5v)
A2 |2 21| A4
A1 |3 20| R/W
A0 |4 19| /CS1
A5 |5 1822 18| OD
A6 |6 17| CS2
A7 |7 16| DO4
VSS |8 15| DI4
DI1 |9 14| DO3
DO1 |10 13| DI3
DI2 |11 12| DO2
+----------+
I include the 1822 for two reasons - it was used in the original Elf (keeping
this reply on topic ;-) and it has the same package size as the 6550, wide
format 22-pin DIP, vs. standard (0.3") 18-pin DIP for the 2114.
I've been lucky enough to find some old printers and such with older RAMs
in them (No... they weren't working). I have no ready sources for bulk
buys of old RAM.
-ethan
21 Nov
21 Nov
11:03 p.m.
New subject: 6550 vs. 2114 (was Re: Elf99 - rebirth of a classic)
On Mon, 16 Nov 1998, Pete Turnbull wrote:
Ugh! Obviously my information source was incorrect, or he was talking
about the chips in a vaguer sense than I though.
Ack! I need a
bunch of these to get a PET 2001 going (all of the 6550s
are bad, and I was told that the 2114 is the same part?) and a VIC 3K RAM
Expander fixed.
They're NOT the same. I can't find a pinout, but they're a different
(physical) size and ISTR they use different voltages as well. MPS6550s will be very hard to find as they were never
second-sourced by
anyone, as far as I know.
So even memory becomes a 'custom chip' from Commodore. :)
They're 22-pin (0.4" wide instead of
0.3") 4096-bit (1024 x
4) SRAMs. 2114's are 18-pin 4096-bit (1024 x 4) SRAMs.
If I had some extra 2114s sitting around, I would have known this by now.
I see they are both 1024 x 4 SRAMs, so maybe something can be done to get
them to work.
Even MOS Technology didn't make them for very
long, which is why only the
earliest PETs used them.
I only have two PETs, and both of them use 6550s. (Both of them also have
the nice 9-inch _white_ display, too.)
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
--
Doug Spence
ds_spenc(a)alcor.concordia.ca
http://alcor.concordia.ca/~ds_spenc/
9375
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ds_spenc＠alcor.concordia.ca -
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