Does an 8MB Floppy work in the Altair-Duino?

[Walt Perko]

Hi, 

Does an 8MB Floppy work in the Altair-Duino?

IF so, are there any blanks or even full of all the BASIC and .COM programs?

Can somebody please attach one to a response here?  

[Walt Perko]

Hi, 

So does that mean an 8MB Floppy Disk can hold 228 files, while the 5MB Hard Disk can hold 247 files?  

On Sunday, August 7, 2022 at 9:23:30 PM UTC-7 furba...@gmail.com wrote:

i believe the file limit is 228 on 8mb

and 247 is the 5mb limit.

On Monday, August 8, 2022 at 12:16:52 AM UTC-4 John Galt wrote:

just for fun i deleted my corrupted 8mb partition again and put a fresh copy off deramp again.

took a picture of what you will see on bootup.

the 8mb is also patched with the Mp/M multi user tool so you can also create subdirectories using user.

you again have to use sysgen and movcpm to have it expand into a full 64kb system.

you only get the starting tools but you have access to C and D 330kb drives so you can transfer your tools off those disks to the 8mb platter.

and then IObytes has to be manually changed on each cold boot if you have devices that require it like a external printer or a tape reader for example.

the 5mb platters work with the IObyte patch information but it doesn't work with the 8mb platters.

On Monday, August 8, 2022 at 12:03:31 AM UTC-4 John Galt wrote:

yes the 8mb floppy works, you have to mount it as a disk drive not a hard drive. then use the floppy boot rom to load into the 8mb partition

https://deramp.com/downloads/altair/software/8_inch_floppy/CPM/CPM%202.2/FDC+%208Mb%20CPM%202.2/

you can find the BLANK and CPM 56kb from deramp.

as memory serves me there is also i big limitation with IOBYTE. the documentation on DERAMP gives you instructions to modify the IOBYTE for the devices on startup and the Data lines up with 

the tutorial however when you use DDT and apply it ruins Cp/M on the next start up. i remember this now i was playing around with it for a few days and i kept corrupting the 8mb partition every time.

the modification works fine with the 5mb partitions but does not work with the 8mb partitions.

that means you have to remember to manually change the IOBYTE after startup to map all your attached devices with the STAT command.

you cannot mix the 5mb and 8mb partitions together because 5mb uses the Hard drive rom and the 8mb uses the floppy rom to boot either configuration can only have 2X5mb+2X330kb drives or 2x8MB+2X330kb drives.

so you can't take the good 5mb IOBYTE and stick it on the 8mb drive and fudge it.

i forgot where on deramp i found the IOBYTE documentation but it didn't work for me and kept corrupting the 8mb cp/m

now from Deramp you get a blank 8mb and the cp/m 2.2 56kb 8mb disk.. you will have to use sysgen and expand it to the full 63kb on a 64kb system this is covered in the cp/m documentation.

there is nothing on these disks, no extra tools other that the default that came with CP/M.

between the file limitations of CP/M 2.2 on the expanded partitions and reaching file directory name limits before reaching byte limits and the issues with IOBYTE on the 8mb floppy partitions i stuck with the 5mb partitions.

unless you have a huge database file that will suck up megabytes you will max out at around 3megs before you hit the 250ish file barrier anyway so it is kind of pointless.

[Richard Deane]

I am confused in this thread between references to 8MB floppy and 8" floppy. Big difference - please can someone clarify which you are referring to?

Richard

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[Walt Perko]

Hi, 

Some of the old 8" floppy disks could hold up to about 8MB data, while the first few hard disks could only hold 5MB data.  

That is just the initial technology limits were back then.  

[da...@hansels.net]

I'm fairly sure that the 8MB 8" floppy disk drive format was something introduced by Mike Douglas

with his enhanced  FDC+ disk controller for real Altair 8800 machines. It is only available when using
the FDC+ together with the PC based server for disk images. As far as I know, a physical double-sided,
double-density 8" floppy disk has an unformatted storage capacity of 6.4 megabits so it can't possibly
hold 8MB of data. Someone please correct me if I'm wrong.

The AltairDuino currently does not support 8MB floppy disk images.

David

[Walt Perko]

Hi, 

Good correction on old FDD disk sizes ... I had used 8" FDDs on a CDC mini computer back in the day, but never even thought about how much space there was since it was so much more than I ever needed back then for temporary data storage while testing MMDs and SMDs.  

[fridtjof.ma...@gmail.com]

The file limit can be increased:

https://github.com/ratboy666/hd1024

gives 1024 files on the 5MB hard disk (binary patch to Mike Douglas' work). We could go to 2048 files, but I find

1024 to be sufficient. Note that I patched the binary from Mike Douglas, so there is no source code for this.

FredW