gloriouscow on Nostr: Did you know that on the Intel 8088, "IP" is not a real register? That's right, ...
Did you know that on the Intel 8088, "IP" is not a real register?
That's right, nothing on the CPU tracks the position of the currently executing instruction.
Internally, there is a PC register that tracks the next byte to be fetched.
When a return address needs to be pushed to the stack, a special microcode instruction "CORR" subtracts the length of the instruction queue in bytes from the value of PC.
When you edit the value of PC in MartyPC, you'll see the IP "register" update accordingly. If you want to make a manual jump, you can change PC to where you want to go and then click the little "Flush" button to flush the PIQ. You're then ready to start executing from that location.
I'll probably let you edit IP directly and automate the flush for you.
#retrocomputing #emulation
That's right, nothing on the CPU tracks the position of the currently executing instruction.
Internally, there is a PC register that tracks the next byte to be fetched.
When a return address needs to be pushed to the stack, a special microcode instruction "CORR" subtracts the length of the instruction queue in bytes from the value of PC.
When you edit the value of PC in MartyPC, you'll see the IP "register" update accordingly. If you want to make a manual jump, you can change PC to where you want to go and then click the little "Flush" button to flush the PIQ. You're then ready to start executing from that location.
I'll probably let you edit IP directly and automate the flush for you.
#retrocomputing #emulation