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Where's the CPM files
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Paul Bigwood wrote:
I've finally finished my SIO Card - long story!, and it seems to beHi Paul, I format the SD-card in FAT16; but do not pre-load the CP/M files onto it. The computer I'm using is running linux, and it's problematic to load the CP/M files on it because Josh's CP/M explorer is Windows. (I have to get another computer with a working Windows setup to do it). If you look on my website, you'll find the files to load, and the CP/M explorer program to do it. Once you get them loaded, you should be all set! Once CP/M is on the Z80MC, then it has the XMODEM program and can transfer any files or disk images with any PC "terminal" program that supports XMODEM. Lee -- 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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With care cpm explorer runs in wine.
Either case CP/M knows nothing of fat so what many do is create a contiguous 8mb file as a container file and then find out what block address it starts at.? Then CP/M addresses the block directly without fat. So CP/M will not read fat files, the file structure is very incompatible. Its possible to run a utility that does BIOS direct DISK IO and read FAT using a program that knows fat structure but that's only useful to get from CP/M to FAT or FAT to CP/M.? I have that for AmproLB+ and Kaypro4/84 its called DOS.? Obvious the media must be compatible (720K 3.5" floppy was the standard here for that) as back then SD and CF were far in the future.? The program called DOS is on the SC CD but it would need a great amount of work for FAT devices larger than 500mb. SD cards do not care what file format you use.? ?If you partition it you can have multiple CP/M partitions.? Oh CP/M does not use partition table on that media either.? ? Use a freshly formated or new SD (1gb is plenty large) and write a bunch of FAT files of 8MB each then use? a program to get the starting bock address of each.? The CP/M BIOS needs to know [when you code it, or as a default that can be changed for B:/C:/D:... drives] what the block starting address is for a given Logical Drive. Using linux DD is both your friend and feind.? It can write blocks to specified addresses easily but only using great care as it can write blocks to specified? addresses easily (oops wrong blocks or device). Allison |
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Hi Alison, The way I wrote CP/M BIOS on the Z80MC is to open a FAT16 File and use it like a drive. I wanted to use the SD card in a manner that would still let the user read/write files through existing Windows file explorer. I thought about just mapping sectors directly to CP/M but that's far too easy, wasteful and not my style. In CP/M, access to a block is translated to 128 byte disk sectors. The BIOS converts this to a 512 byte sector, and the cluster required, then goes FAT hopping. The 512 byte sector is read into RAM and a pointer to the correct 128 bytes is returned. Of course, I consider the 4 (128 sectors) as cached and new SD card reads are not required. Writing updates the cache and simply flags a "dirty data" condition.? The next read that changes the 512 byte cache will trigger the write back to disk. So, there is a chance that writes don't make it to disk, but since most normal programs in CP/M return to CP/M, the reading of the system sectors should satisfy clearing out the cache. Cheers, Josh
On Saturday, September 26, 2020, 01:57:34 p.m. EDT, ajparent1/kb1gmx <kb1gmx@...> wrote:
With care cpm explorer runs in wine. Either case CP/M knows nothing of fat so what many do is create a contiguous 8mb file as a container file and then find out what block address it starts at.? Then CP/M addresses the block directly without fat. So CP/M will not read fat files, the file structure is very incompatible. Its possible to run a utility that does BIOS direct DISK IO and read FAT using a program that knows fat structure but that's only useful to get from CP/M to FAT or FAT to CP/M.? I have that for AmproLB+ and Kaypro4/84 its called DOS.? Obvious the media must be compatible (720K 3.5" floppy was the standard here for that) as back then SD and CF were far in the future.? The program called DOS is on the SC CD but it would need a great amount of work for FAT devices larger than 500mb. SD cards do not care what file format you use.? ?If you partition it you can have multiple CP/M partitions.? Oh CP/M does not use partition table on that media either.? ? Use a freshly formated or new SD (1gb is plenty large) and write a bunch of FAT files of 8MB each then use? a program to get the starting bock address of each.? The CP/M BIOS needs to know [when you code it, or as a default that can be changed for B:/C:/D:... drives] what the block starting address is for a given Logical Drive. Using linux DD is both your friend and feind.? It can write blocks to specified addresses easily but only using great care as it can write blocks to specified? addresses easily (oops wrong blocks or device). Allison |
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>>So, there is a chance that writes don't make it to disk, but since most
normal programs in CP/M return to CP/M, the reading of the system sectors should satisfy clearing out the cache.<< CP/M bios get signals from the BDOS to determine that for deblocking. The BIOS then only needs to do a "updated" read and the SD will write its cache and get the requested block. Warm-boot should do that as well and Cold-boot should as well as the first thing is a read to login the current directory (usually A:). That should apply both for CP/M deblocking and triggering a dirty cache in the SD (its internal caching). Allison |
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Thanks all,
Working fine now. I downloaded the CPM files from the website and simply copied the contents of the ZIP to the SDcard and then booted the Z80MC with the SIO board but not the FP. Some activity and? then hey presto CPM prompt.? Works fine. Bit slower than I recall my old DEC Robin, but fine. Will have some fun putting Small C and Pascal on to the card.? I've got plans for a Z80 PIO and CTC on my expansion board. Meant to mention that I reversed the pins and sockets on the boards, so that I could plug directly into the CPU board with single core bare wires or male pin back to back breadboard wires, rather than having to use DIP sockets. I also found some 20 way versions of the white connectors from EBay and used those with one 10 way supplied to make the inter board connectors.? Here's a photo of the completed boards. Best Regards Pau l |
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开云体育
I used reverse connectors as well for the olduino/z.? Are you able to put the front panel on top of the SIO?
From: [email protected] <[email protected]> on behalf of Paul Bigwood <paul@...>
Sent: September 28, 2020 11:05 AM To: [email protected] <[email protected]> Subject: Re: [Z80MC] Where's the CPM files ?
Thanks all,
Working fine now. I downloaded the CPM files from the website and simply copied the contents of the ZIP to the SDcard and then booted the Z80MC with the SIO board but not the FP. Some activity and? then hey presto CPM prompt.? Works fine. Bit slower than I recall my old DEC Robin, but fine. Will have some fun putting Small C and Pascal on to the card.? I've got plans for a Z80 PIO and CTC on my expansion board. Meant to mention that I reversed the pins and sockets on the boards, so that I could plug directly into the CPU board with single core bare wires or male pin back to back breadboard wires, rather than having to use DIP sockets. I also found some 20 way versions of the white connectors from EBay and used those with one 10 way supplied to make the inter board connectors.? Here's a photo of the completed boards. Best Regards Pau l |
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Considering the DEC Robin ( I have two) is a 4mhz Z80 with 64K of ram?
with banked boot/terminal roms and slow floppies (TM100s) is the comparison?that's terrible. A long time back I got a dozen of the Z80 board used to make up the Robin, They are 4mhz Z80, 64k of Dram, two 24 pin eprom sockets (2732), FDC and 4 serial ports, basis for a good system. So I took one and put on revised roms and it uses a CF interfaced to the old FDC? socket (no floppies) and its fast ss any 4mhz Z80.?? Having multiple real systems to compare at 4mhz is nice: Allison |
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and 4mhz should be enough for anyone ? From: [email protected] <[email protected]> on behalf of ajparent1/kb1gmx <kb1gmx@...>
Sent: September 29, 2020 12:35 PM To: [email protected] <[email protected]> Subject: Re: [Z80MC] Where's the CPM files ?
Considering the DEC Robin ( I have two) is a 4mhz Z80 with 64K of ram?
with banked boot/terminal roms and slow floppies (TM100s) is the comparison?that's terrible. A long time back I got a dozen of the Z80 board used to make up the Robin, They are 4mhz Z80, 64k of Dram, two 24 pin eprom sockets (2732), FDC and 4 serial ports, basis for a good system. So I took one and put on revised roms and it uses a CF interfaced to the old FDC? socket (no floppies) and its fast ss any 4mhz Z80.?? Having multiple real systems to compare at 4mhz is nice: Allison |
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I've collected and build CP/M systems for decades (over 4)
so I have system that run from sludge slow to current idea of fast. Z80s at 10mhz, Z180s at 12mhz and A Z280 at 10mhz. That and no shortage of S100, Multibus, and SBC systems to run. Biggest bottleneck is mass storage IO, 5.25 floppy generally is slow, many hard disks were not fast.? ?Of all CF is usually fastest (best if 8bit mode) and SD slower as the SD has more protocol overhead and the serializing if not done in hardware is slow.? Of course there are implementation dependencies but the faster?systems usually farm out the disk/storage IO to a slave cpu in some form.?? Speed is good if it can be had simply.? A Z80 running at? 6, 8 or 10mhz can be simple.? All that said why speed is nice to have, I use multiplan, Dbase, smallC, BDS-C, Pascal and a lot of other software like Vedit and speed helps. Allison |
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Allison,?? Lee's ALTAID computer uses a 512K RAM chip, 64K for a full memory map and 448K for a single RAM disk. It's fast to access the disk, but the 8080 itself is just chugging along at 2Mhz. Somethings never change.? I'm guessing in 4 decades from now, it will be the same (if humanity survives). Even back on my XT (or was it on my AT?) I would create RAM Disks and work from them. Today, everyone installs SSD to speed up Windows. Cheers, Josh
On Wednesday, September 30, 2020, 10:30:53 a.m. EDT, ajparent1/kb1gmx <kb1gmx@...> wrote:
I've collected and build CP/M systems for decades (over 4) so I have system that run from sludge slow to current idea of fast. Z80s at 10mhz, Z180s at 12mhz and A Z280 at 10mhz. That and no shortage of S100, Multibus, and SBC systems to run. Biggest bottleneck is mass storage IO, 5.25 floppy generally is slow, many hard disks were not fast.? ?Of all CF is usually fastest (best if 8bit mode) and SD slower as the SD has more protocol overhead and the serializing if not done in hardware is slow.? Of course there are implementation dependencies but the faster?systems usually farm out the disk/storage IO to a slave cpu in some form.?? Speed is good if it can be had simply.? A Z80 running at? 6, 8 or 10mhz can be simple.? All that said why speed is nice to have, I use multiplan, Dbase, smallC, BDS-C, Pascal and a lot of other software like Vedit and speed helps. Allison |
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Yes, that is the case.? My Kaypro4/84 has a 1mb ramdisk, very fast.
The compupro also has a 512K ram disk and hard disks with smart controller, faster even at only 4mhz z80. AT class machines even with then hard disks that the same bottleneck. The 8080, well, it was just slow, though it beat the tar out of the 8008 by an easy factor of 10x or more.? Still for the first system I ever? built it was pretty amazing, then I got to see the 8080 instruction set. Back then the PDP-8 (e or i) was the benchmark used, later PDP-11. Generally at each moment I was pushing for best performance or greatest simplicity.? the Z80 or 8085 generally did that well for most cases.? For less 8049 or 8051. Allison |
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Hi Bill,
Yes it all fits together. There is a problem with the FP on top of the SIO though that I haven't tracked down. The FP works fine but there is a segment 'e' I think it is, that is not lit on all characters. I think its a shorted bit on the SIO board, although they all checked out on with an ohm meter when I was testing before plugging it. The CPU and SIO board work fine, as does the FP even when using the bit banging I/O port on the FP with the CPM. Paul |
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Scott,
Like many of the time performance a was a thing... Exity was only one and that was later.? IN 1980 I setup to make the meanest z80 system I could using 6mhz Z80s that were appearing.? Basic design was? remarkably simple, 4 z80 CPUs each its own board with 64K of ram and a bus access protocol (S100 BUS) to share data or resources? (disks, Serial IO and printer).? ?All of the resources were smart as in each had local Z80, 8085, 8749 (printer buffer) to perform tasks.? The goal was to share IO and offload tasks like find a file or spool to printer.? That meant doing surgery to CP/M to split out parts so that the master cpu (server) did end up with all the work (Bios stuff or BDOS) or running a full copy of CP/M on each or the four cpus.? Lots of interprocess communications, interrupts, plus a little foreground background on each. Basically the box was a bunch of networked (via parallel bus) cpus and service providers. In the end while I ran it for years and proved useful a single faster cpu was not burdened with as much overhead.? It also proved CP/M based software while unaware of the multiple cpus was the actual problem as it was unaware of resources that could be useful.? The hardware was doable and all but software had to catch up.? Multiprocessing and time slice was the realm of PDP-11 and VAX or other heavy iron, the Z80 could but the OS was not yet there. CP/net and MPM made some things easier? but the the existing applications software was still built for 64K (or smaller) spaces and had no idea of extensions or how to use them.? That required something Unix or later and all of the seriously needed larger memory space. Allison |
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Hi Allison:
Thanks for taking the time to explain some of the past design issues and your involvement with them.? Yea, lots of timing and bottle-neck issues for access to resources. Integrated circuit fabrication was still cutting its teeth back then, so things were slow but getting faster. I think NATIONAL SEMI was one of the 1st to design a mutli-processor CPU arrangement using their INS8060 and INS8070 series SC/MP CPUs. I was lucky enough to have a friend (who used to work for QXI, a NATIONAL SEMI rep.) sample me an INS8073 with NS tiny BASIC built into RAM. It was literally my very first CPU board design (?.? In the past decade, I've seen other projects with multiple 8051 cores blazing along at some 400 MHz as well (but not with 12 clock cycles per instr. cycle). To think what you were doing 40 years ago has ALL been stuffed into single-chip "SoC's" (System on a Chip) with quad ARM cores, many megabytes of RAM and FLASH memory and lots of other peripherals happily running at 1200+ MHz (instead of 6 MHz!). Linux to the rescue for multiprocessing as the OS yielded us the (GOOGLE) "ANDROID" virtual JAVA machine user interface. For certain, its been an interesting journey, the past few decades. In many ways, I miss the simplistic nature of computing from back then. :) Peace and blessings, Scott |
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I have a multi processor using the SC/MP both the first 8A500 pmos then later 8073.
I have a board I made up with the Nibble basic rom version too.??Their basic issue was paged the unique 12bit addressing and they were slow compared to 8085 and z80. When you put cores together on the same silicon you likely have access to the internal machine and syncing them gets a lot easier.? The yabut is the software still has to know it has resources and how best to use them to advantage. So getting multiple cpus to work and share data was easy but Multiplan and Editors had not one clue?they had additional CPU(s) to work with so no advantage.? The system software I did take advantage of that but it was far from portable as it had to know about the resource to use it being CP/M BIOS was the first place?for devices? to appear.? THe second was doorbell and system control blocks (SCBs) that were ways to transfer messages, commands, and status.??The first multitask/multi-user boxes built around MPM and CP/M-3 new of networking but the number of thing it could do were again not limited by hardware but applications software so must software at best to print remotely but even then the software was dumb. At the time I was also using VAX and PDP-11 systems with multiuser and multitasking? OSs at their core so as a z80 (z180 and Z280 as well) user it seemed we never got to a more complete and effective OS with applications in the 8080/8085/z80 realm of 8bitters.? For the moment Chromix and UZIunix are left out as both had their own hardware needs and also space limitations to be useful. Then again when you can have a cpu to yourself neither multitask or multi-user was high value save for foreground background multitasking as applied to printing (print spoolers or printer managers).? ?The obvious reason for that is why sit and wait for printer which had value. Oddly the 1802 is one of the early cpus where foreground background and simple? multi task management were both sensible and useful in real time control applications. Allison |
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Hello all...
She's back! It been a while and life intervened...? One of the things was getting a Z80MC to play with. I have over a dozen CP/M systems and a few of my own creation both hardware and highly modified software. CP/M is a very malleable OS and can support more than most think or have tried. So now I have a real Z80MC and the software is done is such a way as to be different from the BIOS and loaders of my experience.? Back then it was floppy, hard disk, Eprom based, and of course IDE/CF based,? With that FAT was never a consideration. I find FAT too tightly tied to PCs and equally as fragile as? CP/M allocation scheme. The other is that FAT offers a hierarchical file system and CP/M can't/doesn't use it. It something I'd like to add to CP/M, that is a way to like from one device/Drive to another (especially on large media). The other is my system the typical disk is 8MB (or 32mb for ZRDOS) and multiple partitions.? ? If all goes well it will be a self development environment for a simpler OS like NSDos, the goal there is to release it from hardware NS* MDS hard sector disk. So it will be a playground for experiments started in some case over 45 years ago. Allison |
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Hi Allison, Welcome back!?? There has been an issue with my implementation of CP/M on both the S100 JAIR board and the Z80MC. I failed to understand one of the drive buffer spaces needed, the space needed to create a bit map of the clusters used/free. I followed the examples in the CP/M books and used 31 bytes which is the size required for the SSSD disks of 256,256 bytes. I have now rewritten the BIOS to expand these buffers to 512 bytes, enough for 8Meg disk file images. The BIOS uses SD Card FAT-16 format to reach the data on the Card.? I could have just used the SD Card in it's raw form, but then you'd need special programs to access the card from a computer.? Since I still use PC's, I choose to use the well established FAT-16.? The BIOS can read and write data into the FAT-16 disk images, but it cannot create any FAT-16 files or extend those files.? It doesn't know how to look for a free cluster and add it to the file chain, or even how to change the file size.? It simply uses the space of the file as it's already allocated in the FAT-16 table.? The BIOS counts through the clusters of the image file as CP/M counts through the sectors and tracks.? There is no skewing, it's 1 to 1.?? I will send you the files directly rather than waste space in the 1802 forumn. Cheers, Josh
On Tuesday, December 5, 2023 at 09:20:54 a.m. EST, ajparent1/kb1gmx <kb1gmx@...> wrote:
Hello all... She's back! It been a while and life intervened...? One of the things was getting a Z80MC to play with. I have over a dozen CP/M systems and a few of my own creation both hardware and highly modified software. CP/M is a very malleable OS and can support more than most think or have tried. So now I have a real Z80MC and the software is done is such a way as to be different from the BIOS and loaders of my experience.? Back then it was floppy, hard disk, Eprom based, and of course IDE/CF based,? With that FAT was never a consideration. I find FAT too tightly tied to PCs and equally as fragile as? CP/M allocation scheme. The other is that FAT offers a hierarchical file system and CP/M can't/doesn't use it. It something I'd like to add to CP/M, that is a way to like from one device/Drive to another (especially on large media). The other is my system the typical disk is 8MB (or 32mb for ZRDOS) and multiple partitions.? ? If all goes well it will be a self development environment for a simpler OS like NSDos, the goal there is to release it from hardware NS* MDS hard sector disk. So it will be a playground for experiments started in some case over 45 years ago. Allison |
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Hi Josh,
Best place is the files section of the group. While use PCs and program them even the older systems are my thing. I still have the old don't you wish you have now what DEC had then. For that I boot the MicroVAX as The OpenVMS Language Senstive Editor LSE and cross platform systems are still cleaner than some of the current PCisms.? Linux made than less painful. The only time I've done SD so far I made FAT file of 256mb on a fresh 1GB device?so that its allocated sequentially.? Then located the staring Block number and addressed the blocks in it as LBA starting at xxxxxxH? to the PC its just a block that's allocated with whatever inside.? The system then doesn't need to know FAT at all.? The PC only created the larger container file and allowed me to know the stating address. The CP/M system populated the container file as sectors starting at xxxxxh.? The PC was involved but minimally to initialize (create Fat 32 container file) the disk. As to BIOS design and storage allocation its not obvious but Alloc is a bit map that has one bit per addressable block for the current allocation size.? I had to figure that out in late 1979 when I got CP/M2.2 after running 1.3 and 1.4 in prior years.? So Alloc map for 8mb using allocation block size of 4K bytes is 256 bytes, allocation block size can be as a large as 16K (32K on clones). For large disks I use either 4K or 8k allocations.? The Allocation size limits possible number of files as it sets a minimum granularity.? So for 8mb using 8K allocation block size limits the disk to 1024 files, for 4K it would be 2048 assuming DIRectory size can accommodate that.? The size of? things in the bios for a given disk as all sorts of interactions.? The CP/M Alteration Guide is rather vague on all that.. Andy Johnson-Larid CP/M Handbook gets into it and helps make it clearer. Once up as per earlier CP/M system getfile and putfile tools of my creation are use to transfer serially via USB serial cable to PCs or real serial (tm) to other non PC systems usually VAX, PDP-11, or CP/M. For the BIOS I use on many systems where the device is LBA rather than track sector I use sectors per track of 4 as the device is typically 512byte sectors and make tracks equal to the size of disk (8MB/512=16384).? Offset is usually 0000 as I typically boot from Eprom (copy ccp and BDOS from 8k eprom).? However offset is not part of the size of disk as literal 0th is the first sector that happens to be directory for X many sectors with data block after that. Hard disks are not removable during operating of system so checked entries will be zero (0) but is used for floppies to insure a media swap is caught before a write which would trash the directory. The next high memory cost item is the disk buffers typically equal to sector size or sometimes block size? I try to keep them small.? For example 512 bytes by 4 drives can easily eat up 2K of valuable ram in a basic 64K system.? Why?? They cannot be shared if doing a disk to disk copy havoc would ensue. That's important as high level languages like C, Pascal, and even assembles want ram to run? fast and most the minimum is 48K (ram from 100h to base of BIOS) as the BDOS and CCP are easily overlaid and reloaded. Sector skew only applies to floppies (rotational delay) and for hard disks and other modern media CF and SD zero (00) makes more sense.? Save having skew table or calculating it.? I stopped building in floppies when IDE hit the streets (as too small and salvage) and drives became cheap.? CP/M itself has a internal math error that limits it to 8mb.? P2dos, NovaDOS, Zrdos and a few others fix that at the cost of must be Z80 CPU.? For those 1GB is the limit and 32Mb partitions makes more sense.? The latter due to the flat file structure.? I've spent more than a little time inside CP/M (and enhanced clones) as sources have been available since 1980. Some of the buffers and other space eaters that the BIOS hides can be burred in mapped ram such as Z80MC has for the first 32K.? I've used that before in? a few of my machines where I strive for faster and larger available ram (usually 62K).? The other trick is if the EPROM is large? as in greater than 16K a bootable image of CP/M, Bios and a system monitor that will load it to ram. One block or mappable ram is low ram and others used to support the BIOS. FYI the z80MC will be paired with a small LCD Display and keyboard as a portable system on battery. Allison |
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Ok, right, this isn't the COSMAC group.?? Thanks.
On Wednesday, December 6, 2023 at 11:28:30 a.m. EST, ajparent1/kb1gmx <kb1gmx@...> wrote:
Hi Josh, Best place is the files section of the group. While use PCs and program them even the older systems are my thing. I still have the old don't you wish you have now what DEC had then. For that I boot the MicroVAX as The OpenVMS Language Senstive Editor LSE and cross platform systems are still cleaner than some of the current PCisms.? Linux made than less painful. The only time I've done SD so far I made FAT file of 256mb on a fresh 1GB device?so that its allocated sequentially.? Then located the staring Block number and addressed the blocks in it as LBA starting at xxxxxxH? to the PC its just a block that's allocated with whatever inside.? The system then doesn't need to know FAT at all.? The PC only created the larger container file and allowed me to know the stating address. The CP/M system populated the container file as sectors starting at xxxxxh.? The PC was involved but minimally to initialize (create Fat 32 container file) the disk. As to BIOS design and storage allocation its not obvious but Alloc is a bit map that has one bit per addressable block for the current allocation size.? I had to figure that out in late 1979 when I got CP/M2.2 after running 1.3 and 1.4 in prior years.? So Alloc map for 8mb using allocation block size of 4K bytes is 256 bytes, allocation block size can be as a large as 16K (32K on clones). For large disks I use either 4K or 8k allocations.? The Allocation size limits possible number of files as it sets a minimum granularity.? So for 8mb using 8K allocation block size limits the disk to 1024 files, for 4K it would be 2048 assuming DIRectory size can accommodate that.? The size of? things in the bios for a given disk as all sorts of interactions.? The CP/M Alteration Guide is rather vague on all that.. Andy Johnson-Larid CP/M Handbook gets into it and helps make it clearer. Once up as per earlier CP/M system getfile and putfile tools of my creation are use to transfer serially via USB serial cable to PCs or real serial (tm) to other non PC systems usually VAX, PDP-11, or CP/M. For the BIOS I use on many systems where the device is LBA rather than track sector I use sectors per track of 4 as the device is typically 512byte sectors and make tracks equal to the size of disk (8MB/512=16384).? Offset is usually 0000 as I typically boot from Eprom (copy ccp and BDOS from 8k eprom).? However offset is not part of the size of disk as literal 0th is the first sector that happens to be directory for X many sectors with data block after that. Hard disks are not removable during operating of system so checked entries will be zero (0) but is used for floppies to insure a media swap is caught before a write which would trash the directory. The next high memory cost item is the disk buffers typically equal to sector size or sometimes block size? I try to keep them small.? For example 512 bytes by 4 drives can easily eat up 2K of valuable ram in a basic 64K system.? Why?? They cannot be shared if doing a disk to disk copy havoc would ensue. That's important as high level languages like C, Pascal, and even assembles want ram to run? fast and most the minimum is 48K (ram from 100h to base of BIOS) as the BDOS and CCP are easily overlaid and reloaded. Sector skew only applies to floppies (rotational delay) and for hard disks and other modern media CF and SD zero (00) makes more sense.? Save having skew table or calculating it.? I stopped building in floppies when IDE hit the streets (as too small and salvage) and drives became cheap.? CP/M itself has a internal math error that limits it to 8mb.? P2dos, NovaDOS, Zrdos and a few others fix that at the cost of must be Z80 CPU.? For those 1GB is the limit and 32Mb partitions makes more sense.? The latter due to the flat file structure.? I've spent more than a little time inside CP/M (and enhanced clones) as sources have been available since 1980. Some of the buffers and other space eaters that the BIOS hides can be burred in mapped ram such as Z80MC has for the first 32K.? I've used that before in? a few of my machines where I strive for faster and larger available ram (usually 62K).? The other trick is if the EPROM is large? as in greater than 16K a bootable image of CP/M, Bios and a system monitor that will load it to ram. One block or mappable ram is low ram and others used to support the BIOS. FYI the z80MC will be paired with a small LCD Display and keyboard as a portable system on battery. Allison |
Lee Hart
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