On 12/06/2010 9:47 PM, Sabrina Kilian wrote:
> Not all cats are elitist fuzz-and-claws. Some fuss when they are more
> than an arms length away from someone. Mine yowls when he has to use his
> litter in the middle of the night, since it means leaving the room.
> Howls on the way out and back, just to wake me up and let me know that I
> am missed. Could do without that, actually.


criticise politeness. :-)

Have you tried talking back to him?


-- 

Best Regards,
	Stephen

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>> I don't know. Maybe it's just because it's Saturday morning and *yet
>> again* I'm sitting all alone in my bedroom feeling bored and lonely,
>> with nowhere to go and nobody to talk to. Perhaps I just need to go
>> listen to some more Neil Sekada or something...
>>
> 
> Don't listen to bored and lonely music when you are bored and lonely.

Apparently I'm listening to a different Neil Sedaka than everybody 
else... The one I have is like liquified sunshine in a bottle.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On 6/10/2010 3:40 PM, Orchid XP v8 wrote:
> nemesis wrote:
>> and you say you're a retard... o_O
>
> Well, I _did_ just spend several weeks building a simulated model of a
> trivially simple computer when I could just, uh, use a real one...
>
> When you think about the amount of _useful_ stuff I could have done with
> that much time and energy, you start to understand why I feel
> unfulfilled with my life. :-(
>

Are you going to re-create the model in Dwarf Fortress? :P

-- 
http://isometricland.com

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...so anybody have anything to say about the design itself? ;-)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Am 13.06.2010 12:44, schrieb Orchid XP v8:
> ...so anybody have anything to say about the design itself? ;-)

* Did you think about how to implement a stack (and subroutine calls)?

* The address space is not only piffling, but outright insufficient, 
especially given the limited instruction set; some things you could do 
about it:

- As your commands are all 2 bytes wide, you can require that they be 
16-bit aligned, so you can increase address space available for programs 
to 512 bytes (=256 instructions).

- You could further increase the total address space by separating code 
from data (Harvard architecture), using two separate "Read" control 
lines. (The CPU could still easily be used in von-Neumann-Mode by ORing 
the two "Read" lines externally.)

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clipka wrote:

> * Did you think about how to implement a stack (and subroutine calls)?

Yes: With great difficulty. ;-)

There are instructions to load and save the PC. Your "stack pointer" is 
going to be a RAM register rather than a CPU register. You'll have to 
manually incriment/decriment it, which will be absurdly tedious. But it 
can be done.

> * The address space is not only piffling, but outright insufficient, 
> especially given the limited instruction set;

Well, there is that.

I'm not seriously expecting to make a usable computer out of it. I'll 
just be amazed if it actually ****ing works at all! Currently it works 
in the simulator, but I don't think the simulator is taking gate delays 
into account, and I'm really not sure how that affects all the 
edge-triggered circuits I've used. (!!) There's also the minor detail 
that even the trivial little design I have now is going to take an 
absurd number of gates to realise in hardware...

> some things you could do about it:
> 
> - As your commands are all 2 bytes wide, you can require that they be 
> 16-bit aligned, so you can increase address space available for programs 
> to 512 bytes (=256 instructions).

In other words, make memory 16-bit addressible rather than 8-bit 
addressible.

> - Harvard architecture.

That could work...

The other possibility, of course, is to just connect up more address 
lines. Makes little or no difference in software, but in hardware I 
suddenly have to put a hell of a lot more wires together. ;-)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Am 13.06.2010 16:23, schrieb Orchid XP v8:

>> - As your commands are all 2 bytes wide, you can require that they be
>> 16-bit aligned, so you can increase address space available for
>> programs to 512 bytes (=256 instructions).
>
> In other words, make memory 16-bit addressible rather than 8-bit
> addressible.

Well, you could do /that/, too, but I was merely thinking of making the 
memory 9-bit addressable, by using a 9-bit program counter and 
automatically shifting the value left by 1 bit (filling with zero) when 
loading an 8-bit value into the PC.

> The other possibility, of course, is to just connect up more address
> lines. Makes little or no difference in software, but in hardware I
> suddenly have to put a hell of a lot more wires together. ;-)

Sure ;-)

You should really have a look at FPGAs if you want to save the money, 
time and hassle of wiring up a hell lot of 74xx gates.

If you want to go for classic 5V logic and thru-hole mounting (as 
opposed to SMD), maybe you won't find a suitably "sized" FPGA to fit 
your whole CPU inside, but you should surely find some PLCC-packaged 5V 
or 3V-5V FPGA to fit at least the complete control matrix; I'd suggest 
the Lattice ispMACH 4A5-64/32 44-pin PLCC for the job, which will give 
you up to 32 I/O pins with optional in- and/or output flip-flops, 2 more 
input-only pins, plus 32 bits worth of flip-flops for internal registers.

That would leave you with one 74xx for each register and each of the ALU 
functionalities to wire up, which should lessen the pain already. 
Alternatively, you could use another ispMACH for the ALU (which might 
also include the X, Y and Z registers), and (if required) a third one 
for all the rest.

Or, if you know how to solder SMD packages (or know someone to do that 
for you), you could go for something bigger, such as an ispMACH 
4A5-128/64 or 4A5-192/96, which should allow you to do all in one chip 
(except the main memory).

(The ispMACH 4 series is officially discontinued - which is a pity 
because I think the M4A5-64/32 was ideal for experimenting given that it 
runs on 5V and fits in inexpensive thru-hole mounted sockets - but some 
devices, including the M4A5-64/32 PLCC, are still available even in 
stock at Lattice, at prices of about 5$ apiece.)

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>>> - As your commands are all 2 bytes wide, you can require that they be
>>> 16-bit aligned, so you can increase address space available for
>>> programs to 512 bytes (=256 instructions).
>>
>> In other words, make memory 16-bit addressible rather than 8-bit
>> addressible.
> 
> Well, you could do /that/, too, but I was merely thinking of making the 
> memory 9-bit addressable, by using a 9-bit program counter and 
> automatically shifting the value left by 1 bit (filling with zero) when 
> loading an 8-bit value into the PC.

Oh right, I see...

>> The other possibility, of course, is to just connect up more address
>> lines. Makes little or no difference in software, but in hardware I
>> suddenly have to put a hell of a lot more wires together. ;-)
> 
> Sure ;-)

I did briefly entertain the idea of a 4-bit design. Certainly my CPU 
loads 16 bits from RAM on every instruction cycle, yet has only 17 valid 
opcodes (not 2^16 or even 2^8). On the other hand, a 4-bit address space 
is about as useful as... um...

> You should really have a look at FPGAs if you want to save the money, 
> time and hassle of wiring up a hell lot of 74xx gates.

I have a sinking feeling that if I went to the [extreme] expensive of 
getting an FPGA rig, I'd probably then find that I'm too stupid to make 
it do anything anyway! :-/

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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SharkD wrote:
> Are you going to re-create the model in Dwarf Fortress? :P

Did you see the post about making DF turing complete? Apparently you can 
connect waterfalls or dwarfs or something to do NAND gates and build an 
entire computer out of it.

Oh, there it is. GIYF.

http://www.boingboing.net/2010/04/15/colossal-turing-mach.html

-- 
Darren New, San Diego CA, USA (PST)
    Eiffel - The language that lets you specify exactly
    that the code does what you think it does, even if
    it doesn't do what you wanted.

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Orchid XP v8 wrote:
> manually incriment/decriment it, which will be absurdly tedious. But it 

Welcome to writing a FORTH interpreter on the 6502!

-- 
Darren New, San Diego CA, USA (PST)
    Eiffel - The language that lets you specify exactly
    that the code does what you think it does, even if
    it doesn't do what you wanted.

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