- READ ONLY MEMORY PICTURES UPDATE
- READ ONLY MEMORY PICTURES UPGRADE
- READ ONLY MEMORY PICTURES SOFTWARE
- READ ONLY MEMORY PICTURES SERIES
READ ONLY MEMORY PICTURES UPGRADE
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JohnU on Reactive Load For Amplifiers Teaches Lessons About Inductors.Nt7Ftr on Reactive Load For Amplifiers Teaches Lessons About Inductors.DivePeak on Buzzword Bingo Bitcoin Burial Burrowing Blueprint Balked At By Bureaucracy.Even with these limitations, this is still a great hack!Ĭontinue reading “ASAP 3 – The Almost Simple As Possible Computer” → Posted in computer hacks Tagged Central processing unit, Digital Computer Electronics, pong, Read-only memory, rom, simulation Making A Diode Matrix ROM corrected this by using a ROM as a look up table replacement for certain ‘181 functions. In certain circumstances the carry bit would not propagate correctly.
READ ONLY MEMORY PICTURES UPDATE
He also found a ( update simulation only) issue with the carry bit on the 74LS181 bit slice ALU. doesn’t have a logic analyzer on hand, so he wasn’t able to track this one down further. Above that, glitches from the ROM chips start triggering the asynchronous inputs in some of the registers. The ASAP-1 is limited to a clock speed of around 500kHz. Even with simulation he still ran into some problems. This is where the simulation mentioned above really saved him some time.
READ ONLY MEMORY PICTURES SOFTWARE
He wrote all the software by hand in his own machine code. The hardware was only half the battle – found writing the software just as challenging. When all was said and done, had over 100 instructions spread over 3 Flash ROM chips. Don’t have a machine instruction you need? No problem – just write one up. Using microcode makes ASAP-3 very flexible. The microcode itself is stored on Flash ROMS.
READ ONLY MEMORY PICTURES SERIES
The ASAP-3’s instruction set is microcode, based upon the 8085 series instruction set. While simulation can’t solve every problem, it can often help in verifying that a given design is sound. His tool of choice was Proteus Design Suite. One thing that can’t be stressed enough is the fact that made his design work much easier by using lots of simulation. His primary design goal was to be able to run a 4 function calculator program.
These computers were beyond his skill levels back then, so he began to build his own system. looked at quite a few of the “modern retro” computers such as Magic-1, Big Mess o’ Wires 1, and the Duo. The architecture is based upon the SAP series of computers from Albert Malvino’s book, Digital Computer Electronics. His computer is the Almost Simple As Possible Computer 3 (ASAP-3). has joined an elite club of people who have designed and built their own computer – including a CPU created from discrete 7400 series logic. Video below.Ĭontinue reading “Homebrew Programming With Diodes” → Posted in classic hacks, hardware Tagged atari, diode, diode matrix, Read-only memory, rom ASAP 3 – The Almost Simple As Possible Computer Repeat this eight times for each byte, and you have possibly the most primitive form of read only memory.Īs for the demo coded up with diodes? It displays a rainbow of colors with a black rectangle that can be moved across the screen with the joystick. Pulling an address line high or low ( hasn’t posted a schematic) pulls the data line to the same voltage if a diode is connected. At each intersection, the data lines were either unconnected, or tied together with a diode. connected a ton of 1N60 diodes along a grid, corresponding to the data and address lines to the 2600’s CPU.
Even better, his diode matrix circuit is actually functional: it’s a 64-byte ROM for an Atari 2600 containing an extremely simple demo program. For the longest time, has wanted to build a ROM out of a few hundred diodes, and he’s finally accomplished his goal. Diode matrices were one of the first methods of implementing some sort of read only memory for the very first electronic computers, and even today they can be found buried deep in the IPs of ASICs and other devices that need some form of write-once memory.
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