Sharp PC-1260 information [slightly OT]

[Nelson M. Sicuro (Brazil)]

Hi all,

I'm now a proud owner of this little marvel: Sharp PC-1260.

I already discover the assembler language of its processor, I need to know more of its hardware.

I opened it and found a little "daughter" board with two 2K SRAM chips (6116) and one 32K ROM (I guess), and there is room on this PCB to "replace" one of the 2k SRAM chips by other bigger (I guess one of 8K).

There is a way to put a 32K chip there? And I'm thinking of build another PCB to "replace" the original with FLASH ROM and SRAM. Any ideas?? Someone as crazy as me?

Best regards,

Nelson

[Pierre Brial]

Hello Nelson,

Congratulations, PC-1260 is truly a great computer-calculator, and you can really put it in a small pocket.

You can actually replace one of the 2k RAM ship with a 8k. You will obtain an home-made PC-1261 or PC-1262.

In the 80's some improved 32k PC-1260 were sold in France and Germany. If you do some successfull experiments please tell me. Here is my address : pbrial**at**ool**dot**fr (despam accordingly).
I will be interested to put more memory in my PC-1261 but these ships are very difficult to unsolder.

Some easiest hardware upgrade :

- you can replace the 768 khz oscillator by a faster one. Success have been obtained with 910 khz, 1000 khz, and 1250 khz. 2000 khz is too fast, the CPU cannot follow. The gain in calculating speed is exactly equal to new_frequency/768.

- if you remove the diode located right to the bottom battery contact, you will have the japanese version. shift+SML activate the japanese keyboard, but you loose the lower case (japanese version can be activated by software too).

Happy experiments

Pierre Brial

[Nelson M. Sicuro (Brazil)]

Hi Pierre

I made a memory map of it, and found many "gaps" in it, and reversed-engineered the memory PCB schematics. It is easy to build a 16KB version, as long as it *does't* use any address between $7800~$7FFF to any keyboard port or something.

The display memory also waste some precious space on the 64KB area, it uses only 256*2 bytes of memory map but repeats itself on a 8KB space! If I can modify this address space in some way I can put about 23.5KB on it. I only hope that the BASIC recognizes it!

Another idea is to build a new memory PCB, with more memory and FLASH ROM, switched on banks with some logic chip (with BASIC extensions and MATH also, matrices, complex numbers??).

Is very hard to find information on these wonderful machines, I found some pages in german and french, but not so "deep" information (thanks to BabelFish!). I think I have to build one myself with my discoveries, I think that it will be the only in portuguese/english...

Best regards!