W65C02 on R1 of the Advanced PCB Remake For the Atari 800XL --- YES, it works! :-)

[reifsnyderb]

Ok.  I turned the system on this morning and everything works fine until I attach the 1091 w/SRAM.  The 80 column card works, though.  Last evening's testing was with all the hardware warm.  Looking through the data sheets, nothing really sticks out.  My best guess is that something is either shifting the timing or voltage slightly due to heat.  The board works fine, with the W65C02, by itself. 

 

The 1090XL and 1091XL both are electrically identical in this situation.  They both have buffers for the address lines, data lines, and some of the other lines.  Since the 80 column board seems to work, and SRAM read access shouldn't be an issue, I think it makes more sense to examine the write timing more closely.

[drac030]

On 11/12/2023 at 5:23 PM, reifsnyderb said:

MULE isn't on the list????    (MULE works!)

I was just testing what I had at hand then.

[reifsnyderb]

On 11/12/2023 at 2:08 AM, phaeron said:

Compatibility issues that I know of between the 6502 and the 65C02:

• Undocumented instructions not supported
• JMP (abs) handles page crossing with extra cycle
• No false reads from the wrong address on page crossing when indexing
• D flag is cleared on interrupt
• Decimal mode takes an additional cycle to produce correct flags
• 65C02 stops on write cycles when RDY is pulled, meaning STA WSYNC will occasionally end one cycle too early, and INC WSYNC will always be one cycle early
• Read-modify-write instructions do two reads and one write instead of one read and two writes -- this invalidates ASL IRQEN style tricks for fast IRQ acknowledgment
• Absolute indexed RMW instructions are one cycle faster when not crossing a page

In theory, if you run a math pack benchmark like SysInfo, it should show the 65C02 running slower than a 6502.

Since I've got another 800XL (remake) running the W65C02, I just confirmed that the W65C02 does benchmark a little slower on the math pack.  The benchmarks are as follows:

 

Addition:  98

Subtraction:  98

Multiplication:  97

Division:  96