5MB files but smaller space on the drive?

[Walt Perko]

Hi, 

Why is it that I BOOT with 

A7 A6 A5 A4 A3 A2 A1

 0    0   0    1    1    1   0

AUX 1 <DOWN>

I expect to see four 5MB disks, instead this is what I have?  

A>LS A:  HDSK03.DSK: Mike Douglas' 88-HDSK CP/M

187 File(s), occupying 1840K of 4852K total capacity
21 directory entries and 3012K bytes remain on A:


A>LS B:  HDSK04.DSK: Infocom Adventures CP/M
100 File(s), occupying 3808K of 4852K total capacity
44 directory entries and 1044K bytes remain on B:


A>LS C:  HDSK01.DSK: Altair Hard Disk BASIC
42 File(s), occupying 286K of 296K total capacity
18 directory entries and 10K bytes remain on C:


A>LS D:  HDSK02.DSK: Walt's Programs & Files
19 File(s), occupying 58K of 296K total capacity
45 directory entries and 238K bytes remain on D:

.

[Walt Perko]

Hi, 

IF you look at these two drives you can see they are not nearly 4.x MB or as it's called a 5MB drive ... and the files on the µSD card are each 4,872KB in size.  

A>LS C:  HDSK01.DSK: Altair Hard Disk BASIC
42 File(s), occupying 286K of 296K total capacity
18 directory entries and 10K bytes remain on C:


A>LS D:  HDSK02.DSK: Walt's Programs & Files
19 File(s), occupying 58K of 296K total capacity
45 directory entries and 238K bytes remain on D:

.

On Tuesday, April 22, 2025 at 9:18:29 AM UTC-7 John Galt wrote:

I believe its actually 4,988,928 raw , then you have formatting and  hidden system files for CP/M and bookkeeping that make it 4,852,000

[Tom Wilson]

That's a CP/M issue. The CP/M BIOS that ships with the Altair-duino hard drive CP/M is set up to support 2 hard drives (A and B) and 2 floppy drives (C and D). 

This stuff is not "plug and pray", like the PC BIOS is. If you want a BIOS that supports 4 hard drives, you'll either have to build it yourself or track down someone else's custom version. 

Tom Wilson
wils...@gmail.com
+1(619)940-6311 

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[Walt Perko]

Hi, 

So is it  A: = HDSK03.DSK  and  B: = HDSK04.DSK  and  C: = DISK18.DSK  and  D: = DISK19.DSK ???  

Drive (0) mounted disk image : DISK18.DSK: Walt's BASIC Games1 Disk5
Drive (1) mounted disk image : DISK19.DSK
Drive (2) mounted disk image : DISK1A.DSK
Drive (2) mounted disk image : DISK10.DSK: Dazzler programs (boots CP/M)
Drive (3) mounted disk image : DISK1B.DSK

(F)orce real-time mode : no
(0) Hard disk unit 1 platter 0 image : HDSK03.DSK: Mike Douglas' 88-HDSK CP/M
(1) Hard disk unit 1 platter 1 image : HDSK04.DSK: Infocom Adventures CP/M
(2) Hard disk unit 1 platter 2 image : HDSK01.DSK: Altair Hard Disk BASIC
(3) Hard disk unit 1 platter 3 image : HDSK02.DSK: Walt's Programs & Files
(4) Hard disk unit 2 platter 0 image : none
(5) Hard disk unit 2 platter 1 image : none
(6) Hard disk unit 2 platter 2 image : none
(7) Hard disk unit 2 platter 3 image : none

This makes me wonder why I would define four floppies and up to eight hard drive platters ???  This makes things confusing as it implies more drives are available.  

Is there a Windows 11 compatible "viewer" that can look inside the .DSK files to see the list of file names?  

.

[Tom Wilson]

Is there a Windows 11 compatible "viewer" that can look inside the .DSK files to see the list of file names?  

Yeah. That was being discussed pretty regularly recently. 

https://groups.google.com/g/altair-duino/c/Cs-hMYkyT5c

This makes me wonder why I would define four floppies and up to eight hard drive platters ???  This makes things confusing as it implies more drives are available. 

You're making the mistake of thinking hardware == software. 

This is the Altair, not a modern Windows 11 or Linux computer. Back in the late 70s, you had to write the software yourself. This included alterations to the operating system for your specific setup. 

Tom Wilson
wils...@gmail.com
+1(619)940-6311 

To view this discussion visit https://groups.google.com/d/msgid/altair-duino/5352804e-46e2-4ca7-9477-f15a34645f3an%40googlegroups.com.

[David Williams]

Also, those formats are not cross compatible. Altair hard disk basic can't read the CP/M ones and vice versa.