Tek 4050 series (was:Re: Questions on the days finds)

From: Philip.Belben_at_PowerTech.co.uk <(Philip.Belben_at_PowerTech.co.uk)>
Date: Mon Feb 15 00:57:56 1999

>>> Yes but what's interesting is that the bit-slice 4052 is software
>>> compatible with the 6800 powered 4051!!! The 4052 is a 16 bit machine.
I'm
>>> guessing that Tektronix used the bit slice CPU so that they could
retain
>>> the same software but gain the power of the 16 bit system.
>>
>>>From what I recall (looking at Philip's 4052 service docs), the
>>instruction set is not identical. There's at least one 6800 instruction
>>missing on the 4052.
>
> That's odd unless they (Tektronix) never used that instruction since
they
> claim the the 4052 and 4054 will run all the 4051 software.

Don't forget that at the user level, the 4050 series were BASIC machines.
Any BASIC program that would run on the 4051 would run on the 4052. Some
of the BASIC programs that needed ROM cartridges on the 4051 would run on
an unexpanded 4052.

Talking of BASIC, I think most of the cartridge ROMs were BASIC extensions.

> Does the 4052 service manual give that level of detail? The one for
the
> 4051 gives NO information on the CPU instruction set other than what was
in

Not much detail, but it explains the addressing modes and lists the
instruction set (although it doesn't tell you what the instructions do).
It explains the CPU architecture, including the microcode format...

> the Motorola 6800 brochure that's included in the manual. Does the 4052
> manual give the entry points of the software routines in the system ROM?

Alas, no. Not a thing. I wish it did!

> The 4052 and 4054s also have a larger address range and more memory,
> that may also be why their ROMs won't work in the 4051.

In part. As I said earlier, I think "software compatibility" meant BASIC
software.

>>At the hardware level, the 4052 is 16 bit. But the microcode implements
>>an 8 bit processor - the 16 bit operations are used for calculating
>>addresses only.
>
> I wondered if they were using all 16 bits for data since they could use
> the 8 bit 4051 ROMs.

The memory management circuitry is a tour de force. Not only does it
handle 16 bit fetches on odd and even bytes, it will decide whether you are
addressing 8 bit wide or 16 bit wide memory and act accordingly. Really
lovely machine.

Yes, the 4052 ROM cartridges are 8 bits wide.

Philip.
Received on Mon Feb 15 1999 - 00:57:56 GMT