Harvard architected MCUs/CPUs: dead?

[magellan]

I used to program 8051 and 80251 MCU's in assembly. These were Harvard architecture MCU's where the data and instruction code were located across separate buses and accessed via separate instructions. The code space was read-only and commonly located in an EEPROM. So are Harvard architected MCUs/CPUs dead in today's world?

I believe the Atari ST might have been a Harvard architected system because the OS was stored on an EEPROM, not in system RAM and I don't think it was copied into system RAM on boot either -- because memory space was tight back then for a GUI.

 

[MisterEd]

I don't know whether the Atari ST used the Harvard or Von Neumann architecture. The Atari ST could run off the internal ROM or boot to an external drive so wouldn't it be using the Von Neumann architecture?

I used to have a couple Atari STs:
Atari 520ST (with 1040ST ROM)
Atari Mega STE (TOS 2.06) 4MB RAM

Atari TOS (The Operating System) debuted with the Atari 520ST in 1985. TOS combines Digital Research's GEM GUI running on top of the DOS-like GEMDOS. Features include a flat memory model, DOS-compatible disk format (starting with TOS 1.04), support for MIDI, and a variant of SCSI called ACSI in later versions. Atari's TOS is usually run from ROM chips contained in the computer: Thus, before local hard drives were available in home computers, it was an almost instant-running OS. TOS booted off floppy disks in the very first STs, but only about half a year after the ST was introduced, all ST models started shipping with the latest version of TOS in ROM.

Atari TOS

Atari TOS - Wikipedia

en.wikipedia.org

A lot of computers back then had their OS or BASIC in ROM. That way out of the box they could boot without a drive. Some of these computers could be upgraded to use a floppy or hard drive.

I also had a TRS-80 Model I which had BASIC in ROM. It also had RAM. However, in order to use floppy drives it had to switch to the Disk Operating System which was located on the 1st floppy disk. That meant the user had to add a 2nd floppy drive for their own use.

 

[magellan]

If the OS is on a ROM but the applications are in RAM then I don't think that would qualify as a Harvard architected machine.

PC's used to boot to a basic interpreter if there were no bootable floppies or HDD's.

If you're OS is on a ROM though, I'd imagine you would be somewhat insulated against viruses, especially if the EEPROM could be write-protected.