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Micropolis Disk Drives and IMSAI 8080


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  Micropolis Disk Drives and IMSAI 8080 by Bill Degnan - 04/06/2008 21:20
Summary of recent testing


1) IMSAI with 16K continuous RAM from page 0 (0000H) Cutter Installed on C000. - OK

1.5) I have a bunch of 16 hard sector disks with various labels including a Micropolis BASIC 2.0 MOD 1 Master Diskette of unknown operational status. I do not know if these are operational disks.

2) Micropolis bootstrap loaded into F400 as indicated by manual

3) Pre-load drive behavior is as expected. Cable is attached as indicated in manual

4) Micropolis 1033 I
When I execute F400 H an audible click is heard coming from drive, but no OS is loaded. Drive is continuously spinning. Drive does not attempt to read disk. System display "freezes/holds", and does not return to prompt without STOP/RESET/RUN. Upon RESET, the disk drive responds with another click, but drive continues to spin

Same result if I swap drive 0 for drive 1. - conclusion - controller issue
It appears that the drive is hooked up correctly, and even though OS does not load it seems like the drive to computer communications are at least partially OK.

5) Micropolis 1053 II (the same drive I used years ago in thread about Aeorcomp double density controller / TRS 80 / Expansion unit.)

Repeated test #4 above.

Top Drive when set to 0: does not spin upon depressing drive lever, drive motor does not appear to be working. Head does activate when drive bootstrap is activated from F400. dead?

Bottom drive when set to 0: allllmooost seems to work, may be the closest I have to a working drive. It may simply be that I have no good disks. This drive had worked in the past, but flaky.

6) Micropolis 1042 MOD 1

drive spins when disk is inserted, head DOES NOT activate when the disk bootstrap is executed at F400 H, and drive does not appear to read disk, drive just spins. No error message returned by system, system display freezes until I hit reset on front panel. No reaction from drive upon depressing reset.

Need to doublecheck whether this drive should continue spinning when disk inserted and level depressed. I believe it should.

I have a spare and possibly working 1015-VI F drive that I can swap with the drive

conclusion - controller issue, swap drive if 1015 is compatible replacement.



MORE NOTES: checked memory location 5ED7 H, the memory location where the OS load result code is stored according to the manual. In my system 5ED0-5EDF is properly assigned and non-protected RAM. Whatever value is in data location 5ED7 does not change upon activating the disk boot ROM. My conclusion, you don't get a result code until the system at least detects a disk is bootable.

It's possible that I have single-density disks and with a double density drive (the II next to the model tells you whether it's I= single or II=double density) and I will not be able to boot. The manual states that you can't boot double density disks in a single density drive and visa versa.

1) I could make the hypothesis that the 1053 II bottom drive is OK, but the disks are single density and incompatible with the drive. I should try to buy a single density Micropolis disk drive, or repair my 1033 I. THe other angle is to get a known-working diskette from a double density micropolis 10xx II series drive.

2) replace the drive presently in the 1042 I with the 1015 IV. Don't know if they are compatible, but next is to find this out.

  Micropolis docs by Bill Degnan - 04/15/2008 19:21
Inventory of DOCS on hand and related to this thread:


1040/1050 SERIES




"Micropolis Disk Drives
Microcomputing Nov 1979
by Thim Hogan




1040/1050 SERIES




I see no evidence of "double sided" drives, these are all single sided drives

  Micropolis 1015 IV by Bill Degnan - 04/15/2008 21:33
the 1015 IV are not compatible, too new.



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