Posted By
Litwr
on 2016-09-21
07:34:35
|  Re: What would I do differently in the Plus/4
IMHO Plus/4 is almost perfect for its price and architecture. I am even sure that C+4 cursor keys have the perfect design, the better than other PC. They could only use the quadruple frequency at the borders instead of double. However C+4 gives about 70% of all ticks to CPU, BBC Micro and Apple ][ only 50%, C64 - 40%. So C+4 is the best here, only some z80 systems use CPU better.
80 columns text requires a special RGB-monitor, not TV set or Commodore composite monitor. However, 64x32 bw text is the possible option. 6509 for 1 MB of addressable memory might be an interesting option too.
[Education] Commodore PET started the era of PC in the education (together with much more expensive and not suitable for school Terak 8510/a). CBM didn't try to keep this position and gave it up to Apple...
[CMOS 6502] It executes JMP ($1FF) not the same as NMOS/HMOS 6502. IMHO 65C02 was a step in the wrong direction. It makes slower decimal mode even more slower. It implements a lot of opcodes with very little usability - it was the great opcode space waste preventing the further expansion.  It can't use the several usable undocumented opcodes of 6502 which are used widely by software for C64/+4... I tried to convert some my codes to BBC Master - 65C02 codes had become only 2% shorter. 65C02 has the several very good instructions (BIT#, DEA, INA) though...
So the way to improve C+4 is to change the Commodore architecture at all.
[6502] Delete useless decimal mode and overflow flag. Add new powerful instructions instead, for example, with the second accumulator (like 6800) or addressing mode (#,x) - take the high byte of address from the immediate operand and low byte from the index register.
[disk drives] add more RAM to them. So they maybe used as the additional processors. I would like to use the real multi-thread +4 programs. 
[1571] It can't be fast with +4. Its high speed (5500 bps!) is accessible only from 75% of C128. So 1581 is better for the better storage capacity. 
IMHO Commodore was like a technology terminator. It killed 6502 CPU line, VIC-2 might be upgraded too, 1 MB floppy drives for cheap DD media were not popularized by more affordable price, VDC is the typical example of this poor fate, C264 ... It could even terminate the great Amiga PC.
Sorry if my English is a bit wrong.
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