Build your dream computer

Anything relating to non Sinclair computers from the 1980's, 90's or even before.
Joefish
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Re: Build your dream computer

Post by Joefish »

Maybe better use of the Attribute byte could be 5 bits for INK (2 red, 2 green, 1 blue) and 3 bits for PAPER. So 32 colours (the left and right columns of that 64-colour palette) on 8 backgrounds.

Or 2 blue bits, 2 green and one red. Though I can't think what that palette would be...
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1024MAK
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Re: Build your dream computer

Post by 1024MAK »

When talking about better graphics, one thing that often does not get mentioned, is how a Z80 could manage to shift all the data required for a multicoloured high resolution display around. So I’ve wandered if having two Z80s would help. One would run the game play and feed data to a SID like sound chip.

Meanwhile the second Z80, under the direction of the primary Z80, would exclusively handle the graphics. Be it moving sprites around, or scrolling the screen, left/right/up/down...

This idea could even be extended if the video ULA allowed transparency, then the primary Z80 could do sprites while the second Z80 did the scrolling and other video effects.

And much more flexible interrupt timing would allow the programmer to select which TV line start he or she would like an interrupt to fire on ;)

At the very least, 8 bits for the ink colour, 7 bits for the paper colour (1 bit does the transparency). Same resolution and screen layout (but twice the attribute memory area) as the ‘classic’ ZX Spectrum.

A two colour bit mapped high resolution mode: 640 wide mode. Only allowed two colours per video/pixel line, but a two byte palette entry at the start of each line enables each video line to have different colours to those above or below it. This mode allows for 80 column text.

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RMartins
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Re: Build your dream computer

Post by RMartins »

For me I would like something like:

- CPU eZ80
it's an 8 bit CPU fully compatible with Z80, but supports 24 bits addresses (16MB) as a linear memory addressing mode, or the regular 64K mode.
It has an extra 8 bit register, for all the known 16 bit register pairs we know from Z80.
This would avoid any messy bank switching requirements, like we have on 128K or ZXNext

- up to 16 MB RAM

- Sound should have at least 8 channels, with some control for trebble, attack, sustain, the usual stuff for generating good audio.
Interrupt/DMA driven, to feed the music at any rate required.

- Graphics could have the same resolution or go for 320x240 (keep 4/3 ratio)

- Keep 2 color per 8x8 square.

- 32/16 Color palette (4 bits Ink/ 4 bits paper), but allow this palette to be defined, with 6x6x6 or 8x8x8 RGB palette table.
Eventually the same 4 bit color code, could be a different color, if it was used as paper or ink, giving in fact a MAX of 32 simultaneous color system.

- Dual Port memory, to separate video rendering accesses from regular CPU accesses.
Gets rid of contention timings.

- Support programmable interrupts correctly, per device and programmable timer.
Allows to trigger code execution at specific scan lines for example.

- Support a DMA chip.
For faster screen dump/transfers.

- Provide some form of flash drive support
MicroSD memory cards or similar.


Nice things to have:

- An extra processor, independent of the eZ80, for example a Z80 or 6502 for managing sound, blitting, other system tasks, read keys, etc...

- Keyboard controller with interrupts
So that we don't need to scan the keyboard, it notifies us of changes. Could be done, with the extra CPU.

- Simple blitter chip, that could do the usual basic Porter Duff modes (AND/OR/XOR, AKA Masking), while doing transfers (DMA operations), would be nice.

- Have a RTC (Real Time Clock)

- Support WIFI
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Stefan123
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Re: Build your dream computer

Post by Stefan123 »

My Spectrum dream computer is already here: the Spectrum Next :) The only thing I would have changed is to let it have a larger keyboard.
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1024MAK
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Re: Build your dream computer

Post by 1024MAK »

Some nice ideas there, but the first post did say that we should be using 1980s technology...

The eZ80 was introduced in 2001. EEPROM / flash memory etc. also is relatively new technology. Same with the FPGA with the Next...

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PeterJ
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Re: Build your dream computer

Post by PeterJ »

It's so true that men never read instructions :D
Being an exceptionally gifted individual you can take aspects of any 8bit home computer of the time and build your own. What aspects of what computers would you take?
PS. Thanks @1024MAK!
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Lethargeek
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Re: Build your dream computer

Post by Lethargeek »

PeterJ wrote:
Wed Sep 16, 2020 10:27 am
Imagine if you would that you are back in the 1980s and have access to all the home computers of the time. Being an exceptionally gifted individual you can take aspects of any 8bit home computer of the time and build your own. What aspects of what computers would you take?

To get you started...

It would obviously have to be a Sinclair machine, and have the competitive price point.
then here's my understanding of what was really possible in 1982 at about the same cost but much better (for a home computer)...
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
The excellent BASIC of the Spectrum
To me, all of them BASICs of 80s were unusable and horrible, worse than assembler, so definitely not. Something like Sinclair Logo in appearance (but not in efficiency)) instead. I mean - structured, no line numbers, named procedures, local variables, better machine code integration so it would be of some use in games as well. And yes, it was possible to cram such interpreter into 16k ROM.
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
along with the colour palette and attribute clash
Attributes w/o almost useless flash with 4 bits per ink and paper instead. No 16k model (it was a big mistake) so it's possible to have more memory for the screen. Different screen memory layout with 256 byte chunks representing columns (both pixels and attributes in 2 areas of the each). Several submodes depending of how much lines per attribute you need - from 28 rows (224 pixels high) of 8x8 attribute tiles to 128 pixels high multicolor 8x1 "tiles". Also any width (in attribute columns) you want (you may hide unused columns with ink=paper just like it is done on the real Spectrum). Same ULA memory page mode read trick is possible with the same timings (at the same raster width). Not to mention it's so much easier to program, and the code would be faster too. 8-)
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
The keyboard entry choices of the Spectrum 128K

The built in Floppy Disk of the +3
probably too costly in 1982
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
The Sprites and Sound of the C64, but with additional Spectrum BASIC commands
Sprites? We need no stinkin' sprites! :evil: Hardware sprites were too limiting for the designer, too costly on many levels and inappropriate for an universal computer. To get rid of the colour clash it's much cheaper to implement a low resolution "blocky" 4-color local mode. That is, per attribute tile - if the attribute has ink=paper then it means the tile is in low-res and the ink (or paper) selects one of 16 4-colours local palettes (probably predefined in the 1st models, customizable in the later ones; if ink=paper=border then it just hides this tile gfx).

Likely won't even need the hardware scrolling, as the gfx routines would be even faster than those of the real Spectrum. And to make it even faster it's useful to have programmable interrupt time (a better alternative to using floating bus trick).

Sound yes, i'm not a big fan of AY myself, so SAA1099 at least (if it was impossible to get SID).
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
The build quality and keyboard of the Memotech MTX

The built in SCART Connector of the Sony MSX
again, not sure if it wasn't too costly, but something besides RF is definitely needed (RGB seems a simplest choice)
PeterJ wrote:
Wed Sep 16, 2020 10:27 am
The 320 X 200 resolution of the C64 with 16 colours on screen (with 1 background and 1 foreground colour per 8x8 cell)
see above

as for a better (more natural) fixed 16c palette - something like this one:
Image
(just a rough example that needs more tweaking to allow better mixed gradients)

P.S. and maybe the 6809 (6309 even better, but not sure when it was available) instead of the Z80 if it isn't too radical :mrgreen:
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PeterJ
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Re: Build your dream computer

Post by PeterJ »

Don't forget @Lethargeek, we are choosing from stuff available in 8bit home computers of the 80s.

I hear what you say about BASIC at the time, but probably Sinclair and BBC BASIC were the best during the 8Bit computer boom.of the 80s IMHO.
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Lethargeek
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Re: Build your dream computer

Post by Lethargeek »

PeterJ wrote:
Thu Sep 17, 2020 10:41 am
Don't forget @Lethargeek, we are choosing from stuff available in 8bit home computers of the 80s.
well, i didn't - all the tech was there at the time and the machine using it should have been cheaper than the c64 or the atari 800 (at the very least) while looking almost as good (sometimes better) running games
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catmeows
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Re: Build your dream computer

Post by catmeows »

Lethargeek wrote:
Thu Sep 17, 2020 10:53 am
PeterJ wrote:
Thu Sep 17, 2020 10:41 am
Don't forget @Lethargeek, we are choosing from stuff available in 8bit home computers of the 80s.
well, i didn't - all the tech was there at the time and the machine using it should have been cheaper than the c64 or the atari 800 (at the very least) while looking almost as good (sometimes better) running games
Yes, that Is where I was aiming my design ;)
I'm not sure how far you can go with the BASIC interpreter. I know typical 80ish BASIC was quite horrible but also very accessible. Recently I have studied almost any BASIC from 80s, from TINY BASIC to MALLARD and QL BASIC and it is really interesting how structured BASICs blurs the concept of 'programming for everybody'. Well, I don't want to hijack this thread but if you are interested in designing a 'perfect 16K BASIC', I would like to play with you.
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