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 Forum: General Discussions   Topic: It's not getting any easier

Posted: Sun Jul 14, 2019 11:20 am 

Replies: 11
Views: 2553

Hi All, This weekend I decided to port Mike Chamber's 6502 emulator code, complete with EhBASIC ROM image to run on the Nucleo 743H dev board. The task was simple and straightforward, with the code running first time. A couple of tweaks to the RAMSIZE and the serial baudrate, and we now have an ARM ...

 Forum: Simulation and emulation   Topic: Emulating the 6502 on a Nucleo board

Posted: Sat Jul 13, 2019 1:50 pm 

Replies: 0
Views: 108

Hi All, I've already mentioned this on the 6502.org forum, but I thought it might be worth posting here too. Around 2011, Mike Chambers developed a 6502 emulator, written in C, that has been ported to a wide range of processors. I came across it a few years ago, when it was being offered as a means ...

 Forum: Hardware in general   Topic: Gigatron - A TTL machine with integrated VGA

Posted: Sat Jun 15, 2019 11:34 am 

Replies: 22
Views: 7421

As an update to the Gigatron TTL Computer Project, late last night, Marcel the project founder announced the development of a 6502 emulator, "v6502" residing in ROM. It's not going to be fast - probably about 1/10th the throughput of a 1MHz 6502, but it can interoperate with the existing v...

 Forum: Hardware in general   Topic: The LD12 - a TTL PDP-8 kit from 1974

Posted: Fri May 31, 2019 5:52 pm 

Replies: 4
Views: 582

Perhaps it should be remembered that by 1974, the PDP-8 already had 12 years of history, beginning with the LINC and the PDP-5 from 1962/63 which originally defined the architecture and instruction set - based on the early DEC logic modules. The PDP-8 followed on from the PDP-5 in 1965 with improved...

 Forum: Implementation and Construction   Topic: IC Clamps for Logic Analyzers?

Posted: Thu May 30, 2019 1:41 pm 

Replies: 3
Views: 464

I found that a lot of the useful things like cables, IC adaptors, test clips and pogo pins are still good value when bought from Chinese suppliers. They use this stuff in their factories, and so their local suppliers produce economical parts. You might wish to have a look on Alibaba or AliExpress or...

 Forum: Hardware in general   Topic: The LD12 - a TTL PDP-8 kit from 1974

Posted: Wed May 29, 2019 3:57 pm 

Replies: 4
Views: 582

Hi Ed, I hope this fills the big gap in the details of the real hardware that was used to support the Prosser and Winkel textbook http://anycpu.org/forum/viewtopic.php?f=3&t=608 I think that the main logic board was intended to support a variety of minicomputer designs, the PDP-8 being just the ...

 Forum: General Discussions   Topic: The Art of Digital Design - useful book resource

Posted: Wed May 29, 2019 1:37 pm 

Replies: 6
Views: 844

Thanks Ed, I have already fallen down a digital "rabbit hole" - and found the complete design documentation to the LD20's predecessor - the LD12 - a complete kit to build a PDP-8 functional clone in TTL, from 1974. I've posted links to this resource under a new topic in the Hardware sectio...

 Forum: Hardware in general   Topic: The LD12 - a TTL PDP-8 kit from 1974

Posted: Wed May 29, 2019 1:32 pm 

Replies: 4
Views: 582

Following my interest in the LD20 - mentioned in "The Art of Digital Design" http://anycpu.org/forum/viewtopic.php?f=3&t=608 After a lot of Googling, I discovered that it had a predecessor known as the LD12. This was essentially a DIY kit for a functionally equivalent clone of the PDP-...

 Forum: General Discussions   Topic: The Art of Digital Design - useful book resource

Posted: Wed May 29, 2019 11:42 am 

Replies: 6
Views: 844

People have used that book to build an actual PDP-8. The book focuses on Top Down Design - and makes use of Algorithmic State Machines. The architecture and logic design of the PDP-8 is covered in sufficient detail in Chapter 7 - and proceeds to present the design of a machine they called the LD-20...

 Forum: General Discussions   Topic: The Art of Digital Design - useful book resource

Posted: Sun May 26, 2019 10:44 am 

Replies: 6
Views: 844

This book by Winkel and Prosser is one of the classic computer engineering textbooks of the 1980s. The first edition (1980) was written at a time when microcomputers were still rare - and the university lab was more likely to have a PDP-8/E minicomputer running experimental equipment, rather than an...

 Forum: Hardware in general   Topic: Gigatron - A TTL machine with integrated VGA

Posted: Mon Apr 29, 2019 5:34 pm 

Replies: 22
Views: 7421

Hi All, This weekend we got two Gigatron machines running at 12.5MHz or better. I managed a rather jittery 12.5MHz whilst Marcel's machine built on a 4 layer board managed 15MHz. The increase in clock frequency means that the video display only takes half of the CPU time, leaving 200 cycles at the e...

 Forum: General Discussions   Topic: Sweet 16 - because everybody loves registers

Posted: Sat Apr 13, 2019 6:26 pm 

Replies: 3
Views: 1356

There has been a fair bit written about Sweet 16 - a 16-bit virtual processor devised by Steve Wozniak in 1976/77 in order to simplify the handling of 16-bit instructions on the Apple 1 - which was an 8-bit 6502 and was somewhat short of registers. Woz devised a virtual 16 bit machine with a bank of...

 Forum: Hardware in general   Topic: Gigatron - A TTL machine with integrated VGA

Posted: Sat Apr 13, 2019 11:22 am 

Replies: 22
Views: 7421

Hi All, I've had my Gigatron for about a year, bought initially to jumpstart my learning about TTL computers. In just 34 basic TTL chips - here was a machine that could compete with commercial machines based on microprocesors, such as the 6502 or Z80, yet had a much simpler and more easily understoo...

 Forum: General Discussions   Topic: An 8 bit TTL CPU in 16 chips: CSCvon8

Posted: Sat Apr 06, 2019 9:20 am 

Replies: 2
Views: 1213

An interesting design - utilising heavily upon the availability of large ROMS The ALU is implemented using a M27C322 2Mx16 bit EPROM and the decode logic is performed using a M27C1024 64K x 16 EEPROM. https://processmodeling.org/theory/electronics/ref/micro/eprom/27C322.pdf This is in a 42 pin DIP a...

 Forum: Hardware in general   Topic: From Nand to Tetris - the Elements of Computing Systems

Posted: Thu Mar 28, 2019 8:31 am 

Replies: 7
Views: 1516

Hi Arne, I agree, the PDP-8 schematics are quite difficult to interpret. You can pick out the basic flip-flops, but it's the vast amounts of surrounding diode steering logic which really confuses the newcomer. It doesn't help that it it is all based on PNP devices with negative supply rails to furth...
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