Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

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C128DCR
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Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

Post by C128DCR » Mon Feb 20, 2017 2:49 am

Hello. I have a original 256 KB 1764 REU.
I want expand to 512 KB, but I do not have 8× 41256 RAM chips. 1×41256 = 256 KB×1 bit, 8×41256 = 256 KB×8 bit.
I have 2×44256 RAM chips. 1 chip = 256 KB×4 bit, 2 chip = 256 KB×8 bit. 2 chips soldering plainer, than 8 chips.
If I installed 2×44256, then 512 KB OK? Not pin compatible.
41256 pinout: pdf1.alldatasheet.com/datasheet-pdf/view/37259/SAMSUNG/KM41256A.html
44256 pinout: pdf1.alldatasheet.com/datasheet-pdf/view/125857/SAMSUNG/KM44C256A.html



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eslapion
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Re: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

Post by eslapion » Mon Feb 20, 2017 2:22 pm

C128DCR wrote:
Mon Feb 20, 2017 2:49 am
Hello. I have a original 256 KB 1764 REU.
I want expand to 512 KB, but I do not have 8× 41256 RAM chips. 1×41256 = 256 KB×1 bit, 8×41256 = 256 KB×8 bit.
I have 2×44256 RAM chips. 1 chip = 256 KB×4 bit, 2 chip = 256 KB×8 bit. 2 chips soldering plainer, than 8 chips.
If I installed 2×44256, then 512 KB OK? Not pin compatible.
41256 pinout: pdf1.alldatasheet.com/datasheet-pdf/view/37259/SAMSUNG/KM41256A.html
44256 pinout: pdf1.alldatasheet.com/datasheet-pdf/view/125857/SAMSUNG/KM44C256A.html
Yes, you can boost a 1764 (of 256kBytes) to 512kBytes using 2 44256.

If you check the pinout of the 41256 vs the 44256, you'll see pins the pins have the same functions except there are 4 DQx pins on the 44256 instead of a separate D and Q (which the REU connects together anyways) on the 41256.

It's only a question of making a small adapter and sending the 3 extra data lines to their respective sockets.

The REC manages DRAM as 2 banks of 256 kBytes. Whether these are 8 chips of 1 bit, 2 chips of 4 bits or even a single chip of 8 bits is inconsequential.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

C128DCR
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Re: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

Post by C128DCR » Mon Feb 20, 2017 6:58 pm

The story:
1- Original unexpanded 256 KB REU with 1764 demodisk RAM test fail. Globe and pound demo OK.
2- Turbo REU tester 1.2 http://csdb.dk/release/?id=109935 The original Commodore test program 256 KB/1 min. Turbo tester 256 KB 23s, bank 1-4 OK.
3- REU-checker OK: http://www.retro-programming.de/retro-w ... -unit-reu/
4- Globe 2016 OK. http://csdb.dk/release/?id=152053
5- Reutozoom http://csdb.dk/release/?id=142258 Req. 512 KB, 1/2 pics OK.
6- Freud http://csdb.dk/release/?id=149560 Req. 512 KB, with 256 KB not OK.
7- Treu love http://csdb.dk/release/?id=144105 Req. 512 KB, with 256 KB not OK.

I built in 2×44256, 80 ns (original 41256 150 ns), but 512 KB not OK. Upper 256 KB not 100%. 2×44256 RAM test was OK with Amiga 500.
With 1764 demodisk 512 KB RAM test fail at bank 4. Bank 4-7 = upper 256 KB.
REU-checker 512 KB OK.
Globe 2016 not OK, the 1/3 of the picture is wrong. There is garbage on the empty parts.
Reutozoom not OK, the 1/3 of the picture is wrong. There is garbage on the empty parts.
I install RAMDisk, 2014 blocks free. I load 1 program from 1571 = 33 KB. I save this 15× to RAMDisk (500 KB), OK.
I load 15 programs from RAMDisk, and I save to 2×1571 disks. I load all program from 1571 disks, program 1-7 run OK.
Program 8-10, and 12-14 not OK, 11 and 15 OK. Lower 256 KB = program 1-8, upper 256 KB = program 8-15.
But Freud and treulove 100% OK.

SuperCPU 20 MHz + 1764 512 KB Reutozoom 100% OK! Globe not work (illegal CPU opcodes?).
What is the problem?
None of the programs 8-15 could have worked, if one of the 44256 chips would be wrong.

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eslapion
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Re: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

Post by eslapion » Tue Feb 21, 2017 2:32 am

Checking by software is truly meaningless.

What bits fail and in what address range ?

Also, you didn't post any photos of your solder work.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

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Re: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?

Post by C128DCR » Tue Feb 21, 2017 3:40 am

I soldering these 44256 pins direct to PCB: 7-10 (A1-3, 5V), 11-15 (A4-8), 17 (CAS). 1764 board U11 and U15.
The address pins connecting is irrelevant. (I changed 16×4164 to 4×4464 in C128 with address signal mix, no problem, 4464 pin 9 = 4164 pin 8, etc.).
44256----41256 (U11 and U15)
7 A1-------5 A0
8 A2-------6 A2
9 A3-------7 A1
10 5V------8 5V
11 A4------9 A7
12 A5------10 A5
13 A6------11 A4
14 A7------12 A4
15 A8------13 A3
17 CAS-----15 CAS

http://ar.c64.org/rrwiki/images/9/90/17 ... matics.pdf
I bent 10 pins, 1-6, 16, 18-20. I solder 9 wires into pins (pin 5 unused).
The 9 wires connecting:
U11 44256 pins----------1764
1 data1---------------U10 2 Data in
2 data2---------------U11 data in
3 WE------------------U10 3 WE
4 RAS-----------------U10 4 RAS
6 A0-------------------U10 1 A8
16 OE-----------------U12 16 GND
18 data3--------------U13 data in
19 data4--------------U14 data in
20 GND----------------U12 16 GND

U15 44256 data wires = U15-18.

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