41256 DRAM 256K x 1 pinout

DIP-16. Dynamic RAM, 256K x 1

256K x 1 dynamic RAM on +5 V only. Nine multiplexed address bits: pin 1 is A8, which is NC on a 4164; every other pin matches the 4164. It needs all 256 rows (A0 to A7) refreshed every 4 ms. On the IBM 5160 256-640KB board banks 0 and 1 are 41256 and banks 2 and 3 are 4164, all 200 ns or faster.

Open the interactive 41256 pinout

Pins

Pin	Name	Type	Signal
1	A8	addr	Multiplexed address bit 8. NC on a 4164, so a 41256 in a 4164 board needs this pin driven or tied.
2	DIN	data	Data in.
3	/WE	ctrl	Write enable. LOW writes DIN.
4	/RAS	ctrl	Row address strobe. Latches the row address; a RAS-only cycle refreshes the row.
5	A0	addr	Multiplexed address bit 0.
6	A2	addr	Multiplexed address bit 2.
7	A1	addr	Multiplexed address bit 1.
8	VCC	power	+5 V, the only supply.
9	A7	addr	Multiplexed address bit 7.
10	A5	addr	Multiplexed address bit 5.
11	A4	addr	Multiplexed address bit 4.
12	A3	addr	Multiplexed address bit 3.
13	A6	addr	Multiplexed address bit 6.
14	DOUT	data	Data out, three-state; driven only while /CAS is LOW on a read.
15	/CAS	ctrl	Column address strobe. Latches the column address and gates DOUT.
16	VSS	ground	0 V.

Fitted in

IBM XT 5160 Banks 0 and 1 on the 256-640KB board (banks 2 and 3 are 4164)
IBM Portable 5155 Banks 0 and 1 on the photographed board: HY53C256LS-10 (CMOS 256K x 1), a later upgrade; the 64-256KB board takes 4164s in all four banks

41256 DRAM 256K x 1 pinout

Pins

Fitted in

Sources