Search found 8 matches

by C128DCR
Tue Feb 21, 2017 3:40 am
Forum: Help!
Topic: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?
Replies: 4
Views: 5305

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

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 ...
by C128DCR
Mon Feb 20, 2017 6:58 pm
Forum: Help!
Topic: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?
Replies: 4
Views: 5305

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

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...
by C128DCR
Mon Feb 20, 2017 2:49 am
Forum: Help!
Topic: Possible 256 KB 1764 REU expanding to 512 KB with 2×44256?
Replies: 4
Views: 5305

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

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 K...
by C128DCR
Fri Feb 03, 2017 11:46 pm
Forum: Help!
Topic: C128 external function ROM problem
Replies: 5
Views: 7448

Re: C128 external function ROM problem

Noooo. C128 expansion port pinouts. C64, and C128 C64 mode. C128 and C64 mode not same. In C64 mode ROML and ROMH = 8 KB, look Exrom+Game line. In C128 mode Exrom and Game line unused. Making a C64 Cartridge. Making a C128 cartridge. 74LS08 OK, look C64 schematics: 250469 left side. 250469 right sid...
by C128DCR
Thu Feb 02, 2017 11:08 am
Forum: Help!
Topic: C128 external function ROM problem
Replies: 5
Views: 7448

Re: C128 external function ROM problem

Simple. I connect the expansion port ROMH and ROML to 74LS08 AND gate pin 12-13, I connect the output (pin 11) to 29020 flash ROM pin 24 OE, output enable (= 27256 EPROM pin 22). This = U36 internal function ROM. C128 schematics: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c128/c128d...
by C128DCR
Wed Feb 01, 2017 10:09 pm
Forum: Help!
Topic: C128 external function ROM problem
Replies: 5
Views: 7448

C128 external function ROM problem

Hello. I built a 8×32=256 KB internal function ROM (U36) EPROM. Servant, Keydos, Superchip, Super 81 utilities, BASIC 8, TASS (turbo assembler), GEOS128 V2 1571, GEOS128 V2 1581. All ROM OK with 3 switches. I use C128DCR. I modified a C64 EPROM card to external function ROM. I installed a other 256 ...
by C128DCR
Sun Jan 25, 2015 9:25 pm
Forum: Hardware
Topic: Where is it possible to buy new switches to C64, C128, etc.?
Replies: 1
Views: 2521

Where is it possible to buy new switches to C64, C128, etc.?

Hello. Where is it possible to buy new switches to C64, C128, Plus 4, 1541-II, 1581?
I find suitable swithes nowhere. I want to substitute the original switches. I do not want to transform the machine to a some other kind of switch.
by C128DCR
Fri Jan 02, 2015 3:36 pm
Forum: Hardware
Topic: C128DCR C128 section only 12 V usage, without 12 V= problems
Replies: 2
Views: 3198

C128DCR C128 section only 12 V usage, without 12 V= problems

Hello. I bought a C128DCR machine. The PSU faultless, the machine works. I wanted to recognise the function of the machine, I looked at this: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c128/index.html I disconnected the +12 V= and 11 V~ voltages. Why does not start the machine only ...