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Zenith Z-159 "Restore" Help

B

Boomer6345

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May 9, 2012
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Posted earlier about adding floppies to this unit…also posted about adding a clock but that post seems to never have made it to the board. And, of course, I’ve posted my interest in getting an XT-IDE card…my project will not be complete without it! ;)

Anyway…I have several questions for this project….let’s see what you gurus can help me with…

DRAM – I upgraded to populate the memory board with the full 1.2MB (5 banks of 256K each). Couple questions here. First, what speed memory should this machine use? It is an 8 Mhz 8088 running at zero wait states. I thought I read somewhere that this means I need 80 or 100 ns RAM…but the board has 150 ns RAM. That is what I ordered and added and it seems to be working fine. The number on all the chips is D41256C-15. Does that seem fast enough for 8 Mhz and zero wait states?

EMS – this PC’s main memory card has an EMS chip on it…but I cannot seem to get the Zenith emm.sys driver from Zenith OEM MS-DOS 3.21 or 3.30+ to work with it…the system just hangs as soon as I load the driver in config.sys. Any ideas?

Lastly…since it will be weeks or months (years???) before I may ever get an XT-IDE board…I ordered an older “MFM” hard drive and controller. I have the controller…the drive is on the way from overseas.

While I’ve been waiting for the drive….I researched the controller and drive combination and think I may have a compatibility issue.

The controller is: Western Digital WDXT-GEN Assy 61-000222-00
Here is the exact link to the card I bought on eBay:
http://www.ebay.com/itm/110875232615?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

The drive is: Seagate ST251-1

My research shows that is controller is “feature” limited to only support a specific 20MB drive. I went into the controller ROM through debug and started entering my theoretical drive parameter info as if I was going to format my non-existent ST-251-1 and it seems to take everything. But even if I pull off the low level format will the controller not work due to its firmware being hard coded for a certain drive type?

I tried to find other controllers on eBay that support the ST-251-1 drive (which seems like a common drive back in the day) but none of the MFM or RLL controllers seemed to list a drive type with parameters that match this drive. Again…any ideas?

Thanks!

- Ed
 
Looks like I answered one of my own questions about the hard drive. Some more Googling lead me right back to this forum where I saw a post that lead me to the Seagate ST11M or ST11R controller. I just snagged a cheap ST11R controller off eBay and am hoping to run this ST251-1 as an RLL drive. Sure hope the drive works when it gets here since I now have over $50 into controllers for it!
 
Im not sure if the 251-1 will handle 26 sectors per track, i don't think it's a stock RLL drive, doing so will lead to drive failure, or a crap load of bad sectors, you can go the other way just fine, meaning you can use an RLL drive on an MFM controller, but not the other way around

I have one of those XT-GEN controllers, in my zenith Z-158
Try this

Debug
g=c800:005 at the prompt
if you get a bios drive setup screen you will need to enter the proper parameters of the drive, but those WD controllers WILL see a 40mb drive.

you got an alright deal on the controller, but how much did you pay for the drive? especially overseas...
 
k2x4b524[ said:
Im not sure if the 251-1 will handle 26 sectors per track, i don't think it's a stock RLL drive, doing so will lead to drive failure, or a crap load of bad sectors, you can go the other way just fine, meaning you can use an RLL drive on an MFM controller, but not the other way around

I have one of those XT-GEN controllers, in my zenith Z-158
Try this

Debug
g=c800:005 at the prompt
if you get a bios drive setup screen you will need to enter the proper parameters of the drive, but those WD controllers WILL see a 40mb drive.

you got an alright deal on the controller, but how much did you pay for the drive? especially overseas...
Click to expand...


A post in this forum recommended the RLL use of this drive...and some other sites out there confirmed this is common for the ST-251-1...that specific drive seems to work well with RLL. Hope so since I already bought the controller....could not find a reasonably priced ST11M controller.

I got the drive for what seems like a great price compared to other eBay listings...here is the listing:

http://www.ebay.com/itm/270970266454?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Sure hope the drive works....
 
All the -1 versions of the 251 that I ever hooked up to a RLL controller seemed to perform well.

Since they were customer units, I don't know how long they ran reliably, but, I never heard anything from anyone about them dying.
 
k2x4b524[ said:
That i didn't know druid, wht designation did they use for the rll drives? What does the -1 mean?
Click to expand...

I don't remember the exact configuration, but, the controllers I was using, at the time, just used 26 sectors instead of 17. I believe there was a 60 MB drive in the Seagate line that was just a 251 that passed the RLL test.

The -1 was just a later version that was, IIRC, 28Ms instead of 40ms seek timing.
 
The usual designation for Seagate was to add an "R" to the drive number; e.g. ST-251R.

That being said, it wasn't uncommon for non-RLL-rated drives (except for the earlier production) to run just fine as RLL drives. I certainly did it without issues.

Now, if you had a Perstor ARLL controller that squeezed about 32 sectors/track, you might want to be more selective...
 
k2x4b524[ said:
if you get a bios drive setup screen you will need to enter the proper parameters of the drive, but those WD controllers WILL see a 40mb drive.
Click to expand...

Forgot to ask clarification....

So even though my other WD controller (non RLL) is somehow tied to only certain drives....that really means nothing. Once I low level format with the correct parameters it writes those out to the drive and works just fine? Not sure if I want to go the RLL route or not. Weird that my WDXT-GEN card is specific to certain drives but not really.

In fact....I just don't understand how any of these controllers do not work with all MFM drives if they have that low level format routine that lets you enter custom parameters...seems like drive types or specific models would not matter.

Just trying to understand this 25+ year old technology for the first time! Can't believe I got a ST238R working in my first Zenith Z-148 back in 1988 when I was still in high school...either I have forgotten a lot or I was just lucky back then!
 
So...any answers on my DRAM speed and EMS questions?

So...any answers on my DRAM speed and EMS questions?

Seem to have the hard drive questions under control....
 
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