Interesting discussion about the C128's CP/M poor performance

[Gryzor]

https://retrocomputing.stackexchange.com/questions/2361/why-does-the-commodore-c128-perform-poorly-when-running-cp-m

[Prodatron]

Sounds like a nightmare.

Very interesting btw: I didn't know, that the first 18 registers of the second C128 video chip (MOS 8563) are exactly the same like our CRTC registers (Motorola 6845). I only knew about the blitter abilities of this chip (starting at around register 24).
Now I wonder if they made demo effects with CRTC-tricks on the C128.

It's also funny, when he says, that CP/M Plus - with its pure text-based UI - is too slow for CPUs with less than 4MHz .

[Gryzor]

Yeah, noticed that last part myself and I did a double take, but the guy summarizes nicely the combined design... 

[d_kef]

And I thought that CP/M Plus was too slow on CPC!!! Go figure....

d_kef

[merman]

A quick bit of history...

Commodore advertised a CP/M cartridge for the C64, which would have contained a Z80 processor. It was heavily delayed in development, and the company was fined for advertising a product that was not readily available.

It was eventually released, but had compatibility problems with some models of C64 and the newest (at the time) CP/M programs.

As development on the Commodore 128 started, the marketing department started promising "complete" compatibility with the existing C64 software and hardware. One of the biggest issues was the cartridge port. So the idea was taken to include the Z80, add CP/M compatibility to the new 1571 disk drive and add a workaround to the cartridge port to get things like the CP/M cartridge working.

The C128 ended up about 85-90% compatible with C64 software, and a high rate of compatibility with CP/M - at the cost of speed.

[Gryzor]

Thanks for that, I had forgotten about the cartridge story! 

[BSC]

A quick bit of history...

Commodore advertised a CP/M cartridge for the C64, which would have contained a Z80 processor. It was heavily delayed in development, and the company was fined for advertising a product that was not readily available.

It was eventually released, but had compatibility problems with some models of C64 and the newest (at the time) CP/M programs.

As development on the Commodore 128 started, the marketing department started promising "complete" compatibility with the existing C64 software and hardware. One of the biggest issues was the cartridge port. So the idea was taken to include the Z80, add CP/M compatibility to the new 1571 disk drive and add a workaround to the cartridge port to get things like the CP/M cartridge working.

The C128 ended up about 85-90% compatible with C64 software, and a high rate of compatibility with CP/M - at the cost of speed.

Sounds like a true success story  

[BSC]

https://retrocomputing.stackexchange.com/questions/2361/why-does-the-commodore-c128-perform-poorly-when-running-cp-m

• The code in the C128's Commodore supplied CP/M BIOS... is written in such a way that outputting normal printable characters ... follows the LONGEST path through the code (each character is compared to every possible control character before it is decided that it isn't one), even though it is the most common case by far.

Sounds like they hired the least talented programmers on the planet to get the job done

[Gryzor]

Well, after reading Brian Bagnall's awesome books on Commodore, I wouldn't be surprised if it was a single guy working out of a broom closet..