Amstrad cpc6128

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Amstrad cpc6128

Postby tezza on Sat Sep 26, 2015 8:53 am

It's a busy life nowadays but never too busy to kit out a newly-acquired Amstrad CPC6128.

http://www.classic-computers.org.nz/blo ... tockup.htm for those who might be interested.

It's the first time I've played with those 3 inch disks.
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Re: Amstrad cpc6128

Postby SpidersWeb on Sat Sep 26, 2015 11:50 pm

I think it's Amstrad season :) Good blog, I had a good read through earlier. No doubt I'll be referencing that article if I ever get a 6128 in the future (I got a pair of 464's today)
From memory those disks are something awesome like 72KB per side? It's been well over 20 years since I used one.
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Re: Amstrad cpc6128

Postby tezza on Sun Sep 27, 2015 7:42 am

SpidersWeb wrote:I think it's Amstrad season :) Good blog, I had a good read through earlier. No doubt I'll be referencing that article if I ever get a 6128 in the future (I got a pair of 464's today)
From memory those disks are something awesome like 72KB per side? It's been well over 20 years since I used one.

Yea it's gone from a famine to a feast!

Those disks... No me thinks they are around 360k on each side. I'll need to check on the exact capacity but they are 80 track double density.
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Re: Amstrad cpc6128

Postby tezza on Mon Sep 28, 2015 12:03 pm

tezza wrote:Those disks... No me thinks they are around 360k on each side. I'll need to check on the exact capacity but they are 80 track double density.

Ok it seems they are 40 track and about 178k. Since the machine can write/format/read to an 80 track double density 3.5 inch drive I'm assuming it either doublesteps or just uses the first 40 tracks. Probably the latter.
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Re: Amstrad cpc6128

Postby Gibsaw on Mon Sep 28, 2015 1:45 pm

tezza wrote:Ok it seems they are 40 track and about 178k. Since the machine can write/format/read to an 80 track double density 3.5 inch drive I'm assuming it either doublesteps or just uses the first 40 tracks. Probably the latter.

So, being a CP/M derivative, I'd imagine there's a modified DOS hanging around able to use different densities? Or is that just a phenomenon of the TRS80 line?
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Re: Amstrad cpc6128

Postby tezza on Mon Sep 28, 2015 2:19 pm

Gibsaw wrote:So, being a CP/M derivative, I'd imagine there's a modified DOS hanging around able to use different densities? Or is that just a phenomenon of the TRS80 line?

I don't think there is. Single density only lasted until the very early '80s, (the time when the Model 1 was around). After that everything was double density, then later on in the 80s of course "high density". I don't think the Amstrads ever supported single density or high density floppies.

It was also a phenomenon of the BBC micro (DFS (single density) vrs ADFS (double density).) also. One the point of discussion though, did something like PRODOS (for the Apple IIe range) support double density? Or does this term have no meaning with Apple II Disk technology, given it's stripped-down chipset is quite different from other disk controller read/write conventions of the time? Just curious?
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Re: Amstrad cpc6128

Postby SeanKennedy on Mon Sep 28, 2015 7:18 pm

Don't want to show the master up, but have you tried Alien1.4? Looks from the txt file that it can do these Amstrad types:

Amstrad CPC 464
Amstrad 6128 Side 0
Amstrad 6128 Side 1
Amstrad CPC 6128
Amstrad PCW 8512

I remember having a copy of this on 5.25" disk somewhere - great for getting old CP/M disk onto PC. But I dug it up here.
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Re: Amstrad cpc6128

Postby Gibsaw on Mon Sep 28, 2015 10:23 pm

tezza wrote:One the point of discussion though, did something like PRODOS (for the Apple IIe range) support double density? Or does this term have no meaning with Apple II Disk technology, given it's stripped-down chipset is quite different from other disk controller read/write conventions of the time? Just curious?


It's not that the term has no meaning... Just that for a long time, realistically only one basic density was supported by the chipset. (There were others, but they tended to be a bit hamstrung by being only useful to a ProDOS user. 99% of game loaders were expecting a DOS 3.3 derivative and that really was only written for the Disk II, so things stayed static for a long while until some software started needing ProDOS)

I think the Apple II's ubiquity was the source of this, also... Unlike the C64, cassette use on the Apple II stopped almost immediately and the Apple II spread quickly in a very standard disk-based format and attempts to change it would fail because they had no real driving impetus. Look at how minimal the uptake of "superfloppy" type disks were in the PC world, right to the end of the floppy. The ubiquity of BIOS support for 1.44MB (and horribly patchy support for most other things) ensured NOTHING ever really replaced the 1.44MB until it became too small for anything current. Hell, the 1.44MB survived the patchy transition to CD/DVD boot and outlived BLU-RAY. (Seen a BLU-RAY drive in a laptop lately? It's either no-optical drive or DVD "if they must")

Floppy really has only finally died in servers as support for USB boot is reasonably reliable. :)

I could speculate that the early CP/M world had enough different vendors that diversity of density was possible and ended up widely supported, and to some degree, progress was desired and expected... however I digress.

The Disk II supports 40 tracks, single sided, and the DOS normally used 35 of these at 16 x 256bytes per track. I think there was the odd modified DOS that used the full 40, but nothing official. Tended to be restricted to game loaders wanting to squeeze a bit more onto the disk.

It also happened a bit less because where other machines were using MFM encoding, the Apple II's GCR was a bit more efficient. i.e. 140k where MFM would achieve <100k. So for a while, if software was being ported from another platform, the 140k was adequate. It also made it a bit faster (and cheaper) than most drives with the 16 sector GCR implemented pretty much all in the controller. The downside is this fairly optimised chipset knew nothing about MFM until well after the IIgs, so there's absolutely NO CHANCE of ever reading a (native) CPM or DOS disk in a Disk II with the standard controller. (maybe, one of the later "superdisk" controllers, but ... gold plated hens teeth)
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Re: Amstrad cpc6128

Postby tezza on Tue Sep 29, 2015 8:04 am

SeanKennedy wrote:Don't want to show the master up, but have you tried Alien1.4? Looks from the txt file that it can do these Amstrad types:

Amstrad CPC 464
Amstrad 6128 Side 0
Amstrad 6128 Side 1
Amstrad CPC 6128
Amstrad PCW 8512

I remember having a copy of this on 5.25" disk somewhere - great for getting old CP/M disk onto PC. But I dug it up here.

Yes, my problem initially wasn't getting Amstrad files into a PC, it was the other way around. I wanted to get Amstrad disk images onto my real Amstrad disks. I soon found software that could do this (via a 3.5 inch floppy as a conduit), as mentioned in the article.
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Re: Amstrad cpc6128

Postby tezza on Tue Sep 29, 2015 8:17 am

Interesting stuff. Yes, people stuck with "standards" as much as a way to distribute to as wide a market as possible and share stuff which is why the 3.5 inch floppy lasted so long as did that DISK II .

Gibsaw wrote:It also happened a bit less because where other machines were using MFM encoding, the Apple II's GCR was a bit more efficient. i.e. 140k where MFM would achieve <100k. So for a while, if software was being ported from another platform, the 140k was adequate.

Hmm...are sure about this? Most of my machines that use MFM (double density) typically give you 160-180k on a 40 track single sided floppy. Single density (FM) 40 track, single sided disks on the other hand hold only 80k or so.

All these different floppy disk formats on the 1970s-80s are simultaneously both a real pain but also fascinating. A sign of a young industry jostling for position and finding it's legs.

Then there are cassette tape formats of course. :)
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Re: Amstrad cpc6128

Postby Gibsaw on Tue Sep 29, 2015 8:32 am

tezza wrote:Hmm...are sure about this? Most of my machines that use MFM (double density) typically give you 160-180k on a 40 track single sided floppy. Single density (FM) 40 track, single sided disks on the other hand hold only 80k or so.

I had to go back to the book again and you are correct... FM, not MFM. If you're interested, there's a really good chapter on the encoding in the book "Beneath Apple DOS".

The 16 sector GCR was an improvement over the more widely used "standard" (heh) drive that the Disk II chassis was based on, which I think was the Shugart SA 400.

... and an okay floppy format summary at wikipedia here. Doesn't seem to talk about the CP/M world at all though.
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Re: Amstrad cpc6128

Postby Gibsaw on Tue Sep 29, 2015 9:43 am

Coming back to the CPC 6128... Here's something you might like to play with. Looks cool.

https://en.wikipedia.org/wiki/SymbOS
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Re: Amstrad cpc6128

Postby Audronic on Tue Sep 29, 2015 11:25 am

@tezza

Have a look for "" CPCDiskXP v2.5.1 "" - http://www.cpcmania.com - it runs on a PC under XP

It makes up a variety of Amstrad 3.5" disk formats.

It only makes Disks ?? not a file copier to disk ??

Hope that this helps.

Ray (Over the Ditch)
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Re: Amstrad cpc6128

Postby tezza on Tue Sep 29, 2015 11:33 am

Hi Ray,

Thanks. But check my article at the beginning of my thread. That's exactly what I did use. :)
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