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There are two forms of CP/M experience:
? Small, slow and cramped typical of early floppies of 120 and 241K size.
? High performance using fast large media (hard disks, IDE, CF, SD).
The bulk of CP/M systems I've done are:
Z80
64K ram with eprom overlay for boot, system load, hidden bios,? and utility (256K).
IO as needed to get to the world, dual serial is usual? (SIO or DART, or 8251A)
Maybe a PIO or 8255 PPI
A few include either a timer (8253, or similar) or periodic interrupt.
? Time keeping is not required by CP/M but is useful for applications.
Mass storage
? Over time that was floppy,?
? IDE hard disk? (its not that hard especially if you skip the high byte)?
? Later CF? (does 8bit memory mode nicely still can be found often faer bigger than needed)
? and finally SD? (programming for it is a PITA).
Other storage can be EEprom really slow write but fine for read more
than write and Eprom (read only media) or large RAM (Ram disks).
These can be be ports or part of the main address and mapped in
and out.? Ports using 8255 PPI or LS273 are easier, adding a small
counter (7 bits) can make it easier still.
CP/M wants based on experience larger disks in the 1M to 8MB range.
IF the disk used is larger you partition it in the BIOS (there are other ways)
But a hint do not do all 16 possible devices as you are wasting ram 4 logical
drives is a good working number.? NOTE: CP/M 2 can only address a logical
drive of 128x65536 or 8MB (internal math limit).? Any of the CP/M replacements
P2DOS and later can take that to 1GB however with a flat directory stay at 8mb
and partition for 4 working drives.
Serial or simulated serial IO makes it easier for supporting ported apps to
a system.? Memory mapped video adds parts as it hen has to be mapped
in and out and applications need to stick to standard interfaces and that
can complicate software design.? Its easier if the IO looks like the nominal
console of the day terminal (ADM-3 or VT52, Vt100, H19) or something
that has the feel of TTY (yech!).
FYI if you have larger storage you can remap any drives partition.? Hint?leave
the boot drive as boot drive.? CPM can handle any format but for modern
non floppy that means translating to LBA and then doing sector deblocking
as CP/M assumes 128bytes as logical sector and most modern media is 512.
For that I use 16384 tracks and 4 logical sectors per track (for an 8mb "disk").
That helps with the deblocking code and the "track" is then the LBA address
(Plus any offset for partitioning).? CP/M BIOS math is rather archaine in its
explanation for the disk parameter tables.
As a convenience the system can be loaded from Eprom.? I do that all the time
as it makes the system less dependant on getting it initially on media.? The latter
can be a pain with current system with no support or difficult for that.? CP/M
does not care how it gets in ram (its the job of the bios!).? Even loaded from Eprom
its easy to allow for soft loading from disk as a file.
There is enough free and useful software to fill a large disk!? I have about 18mb
of software I use on the AmproLB+(45MB)? and NS Horizon (32mb) hard disks.
Allison
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Not a fan of TMS9918, hard to get too.
As I have a large collection of CP/M base systems...
S100 several... (Altair, NorthStar, Compupro)
AmproLB+
Kaypro 2 and also 4/84
DEC VT180 (z80 board + Vt100)
Osborne portable
Epson PS-8
If one wants to copy classic S100 with front panel do the imsai it was better.
However that died rather fast leaning toward FLoppy based turnkey systems.
Most systems with video or character displays went three ways:
Sinclair ZX80 used the cpu to do it (cheap video), high cpu consumption and only
NTSC, Try to find a monitor.? Also if its small (MC in mint tin) the average 9"
monitor dwarfs it.? Most video systems had upper//lower case.
S100 and friends use either 64Char x 16line (processor tech VDM-1) and similar.
Later ones use 80x24/25? (just more parts).
TRS80 was of the VDM-1 style of 64x16 All upper for base system and later
versions added lower and 80 char.
Epson PS-8 was a 80x8 LCD with 6803 support for the display and random stuff.
Tandy trs80 M100/Koyocera,NEC8200 were all 40char wide by 8 line LCD.
Later ones use SMC5027 or 6545 CTRC chips with all the surrounding glue and
speed parts.
I happen to like a programmed atmega or two (Grant Searle) as it allows for
VGA, PS2 keyboard.
nearly all of the above had chip counts that were not small format friendly.
The most compact and complete is the ELF VT-102? but that needs the
1802 for half the task (ram and DMA refresh).? It also needs atmega for
the PS-2 keyboard.
The above also reflects that if you do video you need a keyboard.
Most common keyboards are now USB.
The alternate path is a 320x240 LCD with a 40 x 20 screen, still need
MPU to make that go.
Allison
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Richard Cini wrote: I do like the VID design, but here are a few things I thought of:
If you don’t have an aversion to using a PLD, a small GAL like a 16V8
might be useful for decoding and would still be period-appropriate.
There are several “new” designs in both the Retrobrew S100 and ECB
designs that use them, and they’re still available online from secondary
suppliers or eBay. I've used PLDs in other designs for clients. They certainly reduce the parts count, and are good for "get it out the door quick" projects. They're great for commercial products that must fit in a certain size, and to keep your design safe(r) from copycats. But they don't have the longevity of generic widely-sourced parts. I still have a pile of disk controller boards I can't build because the parts are no longer available. PLDs also seem less suitable for hobby projects when you *want* people to be able to duplicate it. There are problems finding parts, finding programmers, and writing the equations to program them. They feel like a closed-box solution. For the RAM, if you don’t need 128k, I might consider something like a
Cypress 32kx8 which is in a 0.300” DIP28 (rather than the normal
0.600”). That saves some space. Yes, I use them on several of my kits. Once they got used by the millions in early PCs, they became generic. Lots of sources, and still available new. They enabled another trick: If you look at my 6502 Badge and VIP2K kits, you'll see the 32k 0.3" RAM that hides *under* the 32k 0.6" EPROM. Their pinouts are almost the same, so it's easy to wire up, too. The reason for the 128K RAM on the Z80-VID was to try to make a CP/M system on two boards. One is the existing CPU board, with Z80, 32K RAM, 32K EPROM, and 8-bit I/O ports. The second is the VID board, with NTSC/PAL video, SPI to run an SD-card for "disk storage", and more RAM so there's enough for 64K for the Z80, plus 20K for the video screen. Alas, there are still too many parts to fit on a 3.5"x2" card without PALs, surface mount, modern parts, etc. But hope dies hard; maybe there's a way... Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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I do like the VID design, but here are a few things I thought of:
If you don’t have an aversion to using a PLD, a small GAL like a 16V8 might be useful for decoding and would still be period-appropriate. There are several “new” designs in both the Retrobrew S100 and ECB designs that use them,
and they’re still available online from secondary suppliers or eBay.
For the RAM, if you don’t need 128k, I might consider something like a Cypress 32kx8 which is in a 0.300” DIP28 (rather than the normal 0.600”). That saves some space.
Rich
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Richard Cini wrote:
>
>
> The 9958 is a weird DIP packaging so maybe the 9918. The Retrobrew Computers N8 Home Computer uses it. Looks like the VDP, RAM, three buffer chips and some decoding.
Thanks Rich,
Designing video was "hard" back in the 70s/80s, so there were lots of
specialized controller chips for people eager to get something out the
door quickly. The Motorola 6845 was popular, but each IC manufacturer
had their own. Intel had the 8275/76, RCA had the 1861, TI had the 9958
and 9918, etc.
They all work, but have also become rare and expensive today. I hesitate
to design something with one, unless I have a bucket of them.
So, I'm inclined to follow in the footsteps of Woz, Sinclair, Lancaster,
and other designers who used clever circuits to produce video with
standard chips. I've attached two of my "brainstorms" in this path:
Z80-VID.PDF has 12 ICs, outputs 384x192 pixel NTSC/PAL video (enough for
24 lines of 64 characters), 128K RAM, PS2 keyboard interface, SPI, and a
bit-banger serial port. It's an accessory board for the Z80MC, (kind of
equuivalent to the Z80-SIO), and multiplexes the RAM between Z80 and
video, so the Z80 does not stop while video is being output.
Z80-VIP.PDF has 11 ICs, outputs the same video, but is a complete
free-standing "terminal". It has its own Z80, 32K RAM, 32K EPROM, UART
serial port, and switch matrix keyboard. It uses the Z80's BUSRQ/BUSAK
signals to stop the Z80 while video is being output (so the Z80 runs at
about 25% speed). It's patterned after my 1802 VIP2K
<>, and uses a simple state machine
(counter/EPROM/latch) to create the video.
But both lack "elegance", and have too many parts to fit on an Altoids
card. I could obviously use a bigger board; but keep "scheming" in case
there's a way...
Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
???????? -- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377,
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Richard Cini wrote:
The 9958 is a weird DIP packaging so maybe the 9918. The Retrobrew Computers N8 Home Computer uses it. Looks like the VDP, RAM, three buffer chips and some decoding.
Thanks Rich, Designing video was "hard" back in the 70s/80s, so there were lots of specialized controller chips for people eager to get something out the door quickly. The Motorola 6845 was popular, but each IC manufacturer had their own. Intel had the 8275/76, RCA had the 1861, TI had the 9958 and 9918, etc. They all work, but have also become rare and expensive today. I hesitate to design something with one, unless I have a bucket of them. So, I'm inclined to follow in the footsteps of Woz, Sinclair, Lancaster, and other designers who used clever circuits to produce video with standard chips. I've attached two of my "brainstorms" in this path: Z80-VID.PDF has 12 ICs, outputs 384x192 pixel NTSC/PAL video (enough for 24 lines of 64 characters), 128K RAM, PS2 keyboard interface, SPI, and a bit-banger serial port. It's an accessory board for the Z80MC, (kind of equuivalent to the Z80-SIO), and multiplexes the RAM between Z80 and video, so the Z80 does not stop while video is being output. Z80-VIP.PDF has 11 ICs, outputs the same video, but is a complete free-standing "terminal". It has its own Z80, 32K RAM, 32K EPROM, UART serial port, and switch matrix keyboard. It uses the Z80's BUSRQ/BUSAK signals to stop the Z80 while video is being output (so the Z80 runs at about 25% speed). It's patterned after my 1802 VIP2K <>, and uses a simple state machine (counter/EPROM/latch) to create the video. But both lack "elegance", and have too many parts to fit on an Altoids card. I could obviously use a bigger board; but keep "scheming" in case there's a way... Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Found this... The 9958 is a weird DIP packaging so maybe the 9918. The Retrobrew Computers N8 Home Computer uses it. Looks like the VDP, RAM, three buffer chips and some decoding. Rich -- Rich Cini ?On 7/26/20, 2:44 PM, "Lee Hart" < [email protected] on behalf of leeahart@...> wrote: Richard Cini wrote: > Lee -- I know decidedly unvintage, but you can use an ATMEGA88 as a composite > color video chip... Of course I can. *Any* modern micro can generate video. For that matter, there are many little boards I can buy that do it all for me. Nothing to design, no software to write. But what's the fun in that? :-) I guess it's like doing a jigsaw puzzle. You could just buy the finished picture; no assembly required. But the fun is in the assembly. And for me, the fun is in the design. Not the modern "beat every problem to death with a sledgehammer" approach, but rather the Dr. Dobbs "running light without overbyte" philosophy. So, I set a hard goal for myself, and then see if I can achieve it. How simple can it be and still do the job? For inspiration, I look back on things like the Heathkit H19 terminal (1979), Sinclair ZX80 (1980), and Voja Antonic's Galaksija computers (1982). They all used a Z80 with minimal vintage hardware to produce a terminal with keyboard and video. There are also Don Lancaster's "cheap video" tricks, which mostly centered on the 6502. I have several designs that *almost* fit on an Altoids size card. But none have quite given me that "aha" moment yet. Lee Hart -- "We do these things not because they are easy; but because they are hard." -- President Jack Kennedy, on the Apollo moon mission -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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I was thinking in the context of bang-for-buck more so than the Woz kind of challenge. Most video designs I’ve seen (post Don) use a CRTC like the 6845 or something close. I think they need too many support chips to fit. There are
a couple others on S100 that use TTL but that’s a lot of chips. Same with the TMS9918 used in the MSX and I’m guessing TI designs.
How about something from the Apple I or the Elf? I’m sure you’ve looked at those already, though, and the chips are hard to get if I remember. I’ll page around my archive and see what else I can find.
Get
toggle quoted message
Show quoted text
Richard Cini wrote:
> Lee -- I know decidedly unvintage, but you can use an ATMEGA88 as a composite
> color video chip...
Of course I can. *Any* modern micro can generate video. For that matter,
there are many little boards I can buy that do it all for me. Nothing to
design, no software to write. But what's the fun in that? :-)
I guess it's like doing a jigsaw puzzle. You could just buy the finished
picture; no assembly required. But the fun is in the assembly.
And for me, the fun is in the design. Not the modern "beat every problem
to death with a sledgehammer" approach, but rather the Dr. Dobbs
"running light without overbyte" philosophy.
So, I set a hard goal for myself, and then see if I can achieve it. How
simple can it be and still do the job?
For inspiration, I look back on things like the Heathkit H19 terminal
(1979), Sinclair ZX80 (1980), and Voja Antonic's Galaksija computers
(1982). They all used a Z80 with minimal vintage hardware to produce a
terminal with keyboard and video. There are also Don Lancaster's "cheap
video" tricks, which mostly centered on the 6502.
I have several designs that *almost* fit on an Altoids size card. But
none have quite given me that "aha" moment yet.
Lee Hart
--
"We do these things not because they are easy; but because they are
hard." -- President Jack Kennedy, on the Apollo moon mission
? --
Lee Hart, 814 8th Ave N, Sartell MN 56377,
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Richard Cini wrote: Lee -- I know decidedly unvintage, but you can use an ATMEGA88 as a composite
color video chip... Of course I can. *Any* modern micro can generate video. For that matter, there are many little boards I can buy that do it all for me. Nothing to design, no software to write. But what's the fun in that? :-) I guess it's like doing a jigsaw puzzle. You could just buy the finished picture; no assembly required. But the fun is in the assembly. And for me, the fun is in the design. Not the modern "beat every problem to death with a sledgehammer" approach, but rather the Dr. Dobbs "running light without overbyte" philosophy. So, I set a hard goal for myself, and then see if I can achieve it. How simple can it be and still do the job? For inspiration, I look back on things like the Heathkit H19 terminal (1979), Sinclair ZX80 (1980), and Voja Antonic's Galaksija computers (1982). They all used a Z80 with minimal vintage hardware to produce a terminal with keyboard and video. There are also Don Lancaster's "cheap video" tricks, which mostly centered on the 6502. I have several designs that *almost* fit on an Altoids size card. But none have quite given me that "aha" moment yet. Lee Hart -- "We do these things not because they are easy; but because they are hard." -- President Jack Kennedy, on the Apollo moon mission -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Lee Hart