test-drb September 2008

test-drb@ccmp.vtda.org

220 participants
323 discussions

Single buffered Ethernet adapters Was: OS/2 Warp, was Re: PCjr Telnet Server

by dave＠mitton.com

On 9/18/2008 01:04 PM, cctech-request at classiccmp.org wrote: >Date: Wed, 17 Sep 2008 11:21:02 -0400 >From: Paul Koning <Paul_Koning at Dell.com> >Subject: Re: OS/2 Warp, was Re: PCjr Telnet Server Test - Done! >To: cctalk at classiccmp.org >Message-ID: <18641.8286.275784.301355 at gargle.gargle.HOWL> >Content-Type: text/plain; charset=us-ascii > > >>>>> "Ethan" == Ethan Dicks <ethan.dicks at usap.gov> writes: > > Ethan> Back when NIC weren't $10 each, I remember the easiest to work > Ethan> with (in terms of compatibility) were the NE2000 and clones > Ethan> (NE1000 for 8-bit machines), the WD (later SMC) 8013, and the > Ethan> 3C501, later displaced by the 3C509. ... > >Something to keep in mind is that the 3C501 is an extremely bad >design. It is completely incapable of dealing with back to back >packets -- even just two of them. And of course that's a perfectly >normal situation in any plausible network. > >I remember working on DECnet when these toys came around, and the >request came in to have a "go slow" feature in DECnet to support this >single buffered design. The answer, of course, was "NFW". (Slowing >down at the source wouldn't have helped because the network could >easily cause clumping anyway...) > > paul The problem with the 3C501 (and the InterLAN and Ungermann-Bass, and other I've forgotten about) Ethernet cards of this era where that they only had one packet of memory on them. Once a packet was received, you had to wait until software retrieved the packet and re-enabled the card, before you could get the next. Likewise if you wanted to transmit - you had to disable reception, copy the transmit packet into the card, and then send it. In PCs of that era that was a substantial chunk of time relative to the potential arrival rate of 10Mbs Ethernet. I have a presentation I have given at DECUS, where I analyzed (on paper) what the likely best possible rates for an XT or PC-AT would be. I should scan that in. (highly unlikely I have a machine readably copy! wonder what I prepped that in?) NetWare and NetBEUI driven networks hardly noticed this problem for two reasons: 1) they were Request/Response protocols. They normally did not expect additional packets until they responded, and 2) they were talking to other PCs. Which simply couldn't generate traffic fast enough. With respect to DECnet, the problem came up quickly when we started having PCs make requests from PDP-11 or VAX file servers, using either FAL or the PathWorks server. When pushing data the mini computer could quickly over run the slow PC with a dumb Ethernet card. The rest of the world noticed when TCP/IP implementations got good enough to encounter similar problems with FTP pulls, and PC file servers finally got enough aggregate clients. The workaround in DECnet-DOS was a careful tuning of the buffer pool, and the transport (NSP) credit flow control window algorithms. The delayed-ack mechanism was optionally tweaked to send an ACK immediately upon receiving a packet ahead of the expected next. This typically indicated a lost packet, and usually generated an immediate retransmit. The VAXmate and PCs using the DEPCA card would run rings around these other cards. Because they used the AMD LANCE Ethernet chip with multiple packet buffers in a mapped memory buffer. The DECnet-DOS kernel optimized this by using it directly for it's buffer pool and removing the need for another memory to memory packet copy. With all due respect Paul, I've never asked another DECnet implementation to "slow down", certainly not DECnet-RSTS. But don't get me started on the VMS implementation of async DDCMP. Dave (Mr. DECnet-DOS)

18 years

a new BBS...

by jlobocki＠gmail.com

comcast digital voice still permits you to make dialup modem calls >from what i understand, im guessing some VOIP providers may work as well, since CDV is VOIP, so it may work. http://www.comcast.com/customers/faq/FaqDetails.ashx?ID=2789 On Sun, Sep 21, 2008 at 2:15 AM, Zane H. Healy <healyzh at aracnet.com> wrote: > At 11:45 PM -0700 9/20/08, David Griffith wrote: >> >> Now as soon as I can figure out how to do POTS modem dialing through a >> cell phone, I'll call. > > How much longer will old fashioned modems continue to work with the evolving > phone systems that we have? When it was looking like I'd be forced to move > to Verizon FIOS a couple weeks ago, I made inquiries and learned that if you > have FIOS you can not use a modem. > > Zane > > > -- > | Zane H. Healy | UNIX Systems Administrator | > | healyzh at aracnet.com (primary) | OpenVMS Enthusiast | > | MONK::HEALYZH (DECnet) | Classic Computer Collector | > +----------------------------------+----------------------------+ > | Empire of the Petal Throne and Traveller Role Playing, | > | PDP-10 Emulation and Zane's Computer Museum. | > | http://www.aracnet.com/~healyzh/ | >

18 years

Apollo Guidance Computer

by rdawson16＠hotmail.com

There is the ocasional homebuilt, TTL CPU thread on here. I wanted to make known this guy, John Plutorak, who reproduced the guidance computer in his basement: http://klabs.org/history/build_agc/ Awsome project, take a look. I intend to build one too... Randy Dawson _________________________________________________________________ Get more out of the Web. Learn 10 hidden secrets of Windows Live. http://windowslive.com/connect/post/jamiethomson.spaces.live.com-Blog-cns!5…

18 years

Z80 home brew with FDC

by lynchaj＠yahoo.com

On 9/21/08 5:24 PM, "Alexis" <thrashbarg at kaput.homeunix.org <http://www.classiccmp.org/mailman/listinfo/cctalk> > wrote: > On Sun, 21 Sep 2008 09:37:51 pm Andrew Lynch wrote: >> I have a working prototype on my bench and can read and write sectors and >> format tracks. > > I never worked out how to format tracks on the 8272. It's one of the things > that puts me off using them. Could you describe how it's done? > > The other thing that puts me off is the data clock separator. How are you > doing this? Look at the code for the CompuPro Disk 1 interface. I don't have to code for my CBIOS handy but I recall that you have to establish a 6-byte command buffer (with the right parameters), establish the interleave (if formatting with one) and then loop through all of the tracks sequentially, sending the format command for each track. I used a hardware interleave so that my CBIOS didn't have to do it. The command buffer for my CP/M system looks like this. The fields come right >from the 8272 manual. FMTDAT .DB F_FMT ; format command .DB 00H ;HDS,DS1,DS0 .DB NFIELD ;N (0, 1, 2, 3) 0=128-byte sectors .DB FSC ;Sector count (26,15,8) =1ah .DB 01BH ;SPECIAL FORMAT GPL. .DB 0E5H ;D (FILLER BYTE) Rich -- Rich Cini Collector of Classic Computers Build Master and lead engineer, Altair32 Emulator http://www.altair32.com http://www.classiccmp.org/cini ------REPLY------ Hi Alexis, Rich, Thanks Rich! Yes, Rich has the right command sequence but you also need to send the C, H, R, N to the i8272 for each sector during the execution phase. It is not very intuitive but I got it working last night on my test bench and confirmed it is working with Dave Dunfield's IMD program (Thanks Dave!) and the Catweasel with CW2DMK (Thanks Tim!). For some odd reason it also requires a leading $00 to format correctly which I don't understand either. Basically, it is like writing a sector but you feed it sector metadata as it goes around the track formatting sectors. Note, during execution phase it is not like feeding the MSR/data registers like during the command/result phase. The whole NEC765/i8272 process is kind of screwy IMO and I am struggling to get my brain around it. I have sample code if you'd like to see it but it is an awful mess right now. As for the data separator, I am using an FDC9229 although you could use a FDC9239 I think. The chips are still available but not exactly common. You have to look but you can find them. I have some pointers if you'd like. Actually, Alexis, you'd be the perfect guy for building your own Z80 home brew FDC as you already have done most of this on your other projects. You did an awesome job on your home brew 8080 a while back and your other projects have been great too. Your experience would be a lot of help to the project in putting out a design that not only works but is reliable and flexible. I'd like to support as many hobbyists as possible so I am trying to preserve the hardware "hooks" to support 8" drives, etc. Due to the complexity of this project it could really use another set of eyes to check the design. There are many subtle issues with FDCs that require real hardware experience. One final note, the i8272 data sheet for the FORMAT TRACK command is rather misleading or at least incomplete IMO. I prefer the SMC FDC765 datasheet found on the BitSavers.org site (Thanks Al!). It also has data sheets for hard to find units like the FDC9216, FDC9229, FDC9239, etc. Warning: 45MB FILE! http://bitsavers.org/pdf/standardMicrosystems/_dataBooks/1985_StandardMicros ystems.pdf Thanks and have a nice day! Andrew Lynch

18 years

Sources for unusual d-sub connectors?

by ian_primus＠yahoo.com

Does anyone have a source for 19 pin d-sub connectors? The Apple II used these for disk drives. I haven't been able to find anyplace online that carries these. Any ideas? Similarly, what about 23 pin d-sub connectors (Commodore Amiga disk drive and video connectors)? -Ian

18 years

Sources for unusual d-sub connectors?

by roger.holmes＠microspot.co.uk

> > Does anyone have a source for 19 pin d-sub connectors? The Apple II > used these for disk drives. //e not ][, in Europe anyway. With a ][ or ][+ the drive has a 20 way connector which pushes straight onto the interface card and you trap it between the case and the lid as a strain relief. The //e had a short linking cable inside the case but if you had an old drive you could still do it the old way I think. Roger Holmes.

18 years

Magnetic peripherals (CDC) tape drive

by pat＠computer-refuge.org

I'm looking for any information (like tape cartridge type, capacity, bus interface) on a Magnetic Peripherals BY5A5-F tape drive (part no. 77024231). Thanks! Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

18 years

Z80 home brew with FDC

by lynchaj＠yahoo.com

Hi, If anyone is interested in building a FDC for their Z80 home brew computer please contact me off list. I am building a FDC for my Z80 home brew computer and would like to see how it works for other builders. The design is general enough to adapt to most Z80 systems. It has IDE and i8272 (NEC 765) sections. I have a working prototype on my bench and can read and write sectors and format tracks. It includes a simple disk monitor program for testing the FDC which could be easily adapted to other systems. I would like to improve and refine this design and increase test coverage with other builders. Thanks and have a nice day! Andrew Lynch

18 years

Triple Crown Software needed for my model 700

by robert45140＠gmail.com

Jeff, Do you have access to the software for the 700? Regards Robert

18 years

What is a Smartnet Arnet card?

by dbuhs＠innovioncorp.com

Joe, Not sure how long ago you wrote about the arnet card, but I am looking for one. Dave

18 years

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test-drb September 2008