On 02/24/2013 04:58 AM, Dave wrote: I don't see a crystal next to that chip. The sorta-nearby 24MHz crystal is likely for the floppy controller...but unless that's divided down to feed that possible-8048 chip, it may not be an 8048 because it has no attached crystal. (it can also be fed from an external oscillator, if memory serves...the 8051 definitely can) Maybe reverse-engineer the oscillator wrapped around that 24MHz crystal, then see where it goes. Compare that with the pinout of the 8048...if it goes to pins 2 or 3, that further suggests that Mr. 4430030 may be an 8048. You (Nigel, not Dave) mentioned that you didn't think it was a microcontroller because there's no ROM nearby. Don't put too much weight on that, because the 8048 has an on-chip ROM. -Dave -- Dave McGuire, AK4HZ New Kensington, PA

On 02/24/2013 11:50 AM, Dave McGuire wrote: More likely 8041/8741, same basic MPU part save for it has a bus slave side so it can be used more like a 8255. Obviously with rom/ram and cpu it's programible. 8048 MPU 64byts or ram (24 of which are registers, and stack) plus 1K ram. the 8049 doubles both ram and rom space internal. 8048 is far from fast enough to do a floppy controller. 2.5us instruciton cycle time. It can do the slow stuff like positioning the head and checking door open, side, track000 but moving data, no. Both can. The max clock is is 11mhz for 804x (fastest versions) and 11for 8051 (fast version) of that time. For a floppy data path controller the likely chips are 1793 prior to 1981 and 765 post. and 8mhz was the likely speed unless they used a DPLL (did not appear in use until until after late 82). 8048, 49 and 8041 had the same clock pins. It could be but a reminder the 8048 of the time would have needed external ram for the disk data buffer (at least 128 or 256 bytes) and while the part can address up to 256 bytes of external ram the get-put code cycle is far to slow to keep up with a FDC unless its' single density 8" (64us per byte) The part is FAR TOO SLOW to do bit bashing so an external FDC chip is required to sort out the bits to bytes (765 or 1771, 1793). I might add they are all 40 pin parts (804x, 805x, 1771, 1793, 765) Allison

On Sun, 24 Feb 2013, Dave McGuire wrote: According to my list, the 8048 has a different number: 6833161 8048 MICROPROCESSOR Christian

Since the 8048 has an internal mask-programmed ROM, it would make a lot of sense for the house number to be different for ICs with different ROM contents. HP _certainly_ did this wither their house numbers. -tony