The Sinclair ZX81
Zilog Z80A Microprocessor clocked at 3.25MHz.
1K RAM, expandable to 16K, 32K or 56K.
8K ROM containing BASIC.
Resolution, 32 x 24 characters
1K RAM, expandable to 16K, 32K or 56K.
8K ROM containing BASIC.
Resolution, 32 x 24 characters
The Commodore VIC 20
MOS 6502 Microprocessor clocked at 1MHz
MOS 6560 VIC-1 Co-Pro (video and sound)
5K RAM (3.5K available to the user)
16K ROM
Resolution, 22 x 23 characters / 176 x 184 pixels
16 pre-defined colours
MOS 6560 VIC-1 Co-Pro (video and sound)
5K RAM (3.5K available to the user)
16K ROM
Resolution, 22 x 23 characters / 176 x 184 pixels
16 pre-defined colours
The Texas Instruments TI99/4a
Texas Instruments TMS9900 Microprocessor clocked at
3MHz
Texas Instruments TMS 9929 Co-pro (video/sprite processor)
16K RAM
26K ROM
Resolution, 32 x 24 characters / 192 x 256 pixels
16 pre-defined colours
Texas Instruments TMS 9929 Co-pro (video/sprite processor)
16K RAM
26K ROM
Resolution, 32 x 24 characters / 192 x 256 pixels
16 pre-defined colours
My first computer,
built from kit form by my Dad. The ZX81, and the
ZX80 before it, were the first real affordable
"home" computers. Now, twenty five years on, I can
really appreciate the actual hardware design - the
designers reduced the overall chip count from 21in
the ZX80 down to 4, and so if you were handy with a
soldering iron the kit form ZX81 cost £50, or £70
ready built.
The basic unit came with a whole 1K of RAM, but you could purchase (for an extra £50) a 16K RAM pack that plugged into the expansion port on the back. The original Ram pack was infamous for "rampack wobble" were the somewhat delicate connector could slip away from the expansion port causing the ZX81 to frequently reset.
People think that "Blu-Tak" was invented for sticking up posters - for me it was to ensure that the RAMPACK remained welded to the back of the ZX81!!!
The basic unit came with a whole 1K of RAM, but you could purchase (for an extra £50) a 16K RAM pack that plugged into the expansion port on the back. The original Ram pack was infamous for "rampack wobble" were the somewhat delicate connector could slip away from the expansion port causing the ZX81 to frequently reset.
People think that "Blu-Tak" was invented for sticking up posters - for me it was to ensure that the RAMPACK remained welded to the back of the ZX81!!!
A brief look into some of the computers that helped shape my career
The Commodore VIC 20,
my first colour computer. This time around I had
both a hi-resolution (bit mapped) mode, and a
re-definable character set to play with. Although
custom sprite hardware wouldn't arrive on a
Commodore computer until the C64, I figured out
that by pre-shifting the graphics across character
boundaries, combined with a logical mask I could
emulate sprites, as this technique preserved the
background that the sptite travelled over, would
deal with transparencies and could allow really
fine grained movement of down to one pixel at a
time.
It sounds really "well, a whoop-a-dee-doo" now, but at the time that really was state of the art!
It sounds really "well, a whoop-a-dee-doo" now, but at the time that really was state of the art!
The TI99-4a, an odd
choice of computer I'll grant you. I got my mitts
on one for two reasons; firstly my local computer
shop had become the first UK distributor of it and
they needed some games writing (as there was a
"huge" market in the US and The Oman - neither was
strictly true!), and more importantly it had the
TMS 9929 co-processor which meant hardware sprites.
Just one problem; you couldn't get access to the sprite hardware through its in built BASIC, and you had to buy some serious extra hardware to hit the CPU with some assembler (the peripherals you needed came to around £1,500!). Of course you could use their "extended" BASIC cartridge which got you at the sprite hardware, but as only, well, seven people in the universe had an extended BASIC cartridge it didn't strike me as a money spinner!
Just one problem; you couldn't get access to the sprite hardware through its in built BASIC, and you had to buy some serious extra hardware to hit the CPU with some assembler (the peripherals you needed came to around £1,500!). Of course you could use their "extended" BASIC cartridge which got you at the sprite hardware, but as only, well, seven people in the universe had an extended BASIC cartridge it didn't strike me as a money spinner!