13 Nov
2022
13 Nov
'22
9:44 a.m.
On 13.11.22 07:13, Steve Lewis via cctalk wrote:
I've been looking for a video or image that shows
what font the original
Datapoint 2200 used.
It's not shown in the manual. There is one vintage image with the office
lady and the DP2200 on the desk- but the font isn't very clear in that.
In any modern video about the DP2200, none of them seem to power it on --
which is certainly understandable. From what I've read, the power supply
of that system is prone to failure. Also, the system is hard-coded to load
from Tape 1 -- which means both the tape drive, and tape media, still needs
to be in good working order (which would be pretty rare after this time).
In "the" DP2200 book, it only briefly mentions that the original tape
software was developed "on an HP system" (without any elaboration that I
could tell on which HP system that was).
Nothing in the manual suggests the original DP2200 could "program itself"
(i.e. no built in machine code monitor -- those TTL chips had one strict
boot up sequence: load from tape 1). If there was a read error or no tape
available, I'm curious if any message showed on the CRT.
So, I was just wondering if there was any known pre-1973 Datapoint 2200's
that are still working? (and/or if any HD video of them powered on and
legible font can be seen) Or any other more current system that we know
for sure used the same font?
Thanks!
-Steve
Not only is the powersupply prone to failure, it is also the most dangerous I have ever
seen, and I am hesitant on working it. Primary and secondary sides not separated,
isolation between the two almost nonexistant, many primary nodes exposed. Would never pass
modern safety checks.
But here is a picture of my DP1100, a DP2200 derivative, while it was running a memory
selftest, for a short time in 2021, before the powersupply blew again :
https://forum.vcfed.org/index.php?threads/its-alive-my-datapoint-2200-1100.…
While the DP2200 is hardcoded to start from tape, the DP1100, otherwise identical, boots
from a ROM. This ROM also contains a minimal machinecode monitor. I recovered &
disasembled the ROM and Gordon Peterson, from Datapoint, commented it out :
http://www.bitsavers.org/pdf/datapoint/1100/DisketteBootDisassemblyGEP2.txt
Note that there are multiple videoboard options : the later DP2200, my DP1100, and the
DP5500 share the same videoboard. This relies on a programmable characterset. In the
disassembly mentioned above above, starting at line 3660 you will see a load of
gobldecook, these are actually fondsets to be loaded into the machine.
The fontset has a very particular "look" to it. How much is due to
fontdefinition, and how much is due to the diddlescan, that I dont know. Diddlescan is
where they scan each character in full, before proceding to the next.
Note that a ROM based bootboard for a DP2200 would be a trivial undertaking, and only
involve changing the cassette reader board for the ROM board.
Jos