On 11/1/16 6:39 AM, Peter Cetinski wrote: Depending on the on disk format and the filesystem it can be very hard to do that as you have to know the relative position in the file. What can you do for specific files is to first clean the heads, each and every time as old disks may leave abrasive crap behind and that can kill good media. The other is does the sections not readable actually contain data? Some file systems do scatter/gather so they can efficiently use the whole disk space (CP/M, DOS for PCs to name a few). Then it requires digging into the hard/software to do low level reads without error checking or despite it. For many that goes to a level well beyond trivial. Allison

You are aware that the 8755A and 8755 are programmed differently? I believe the adapter is only for the 8755A. Dwight ________________________________ From: cctech <cctech-bounces at classiccmp.org> on behalf of allison <ajp166 at verizon.net> Sent: Wednesday, November 2, 2016 5:35:08 AM To: cctech at classiccmp.org Subject: Looking for Prompt-475 All, Looking for the schematic for Intel PROMPT-475, this is the 8755 adapter board for the Prompt-48. Allison

It had been a long time since I'd worked at Intel but I recall having to use a different UPP board for each. I worked on the UPP with the 4040 uP. I was a test engineer for its end of life. Debugging these was a pain in the butt so I made what I called a slowtime-ice. I'd replace the 4004 with my umbilical and talk to the various 4002s and 4001. Although, I wasn't suppose to, I had a dump of the ROMs to compare with. We were our own last customer to order 4001s. Dwight ________________________________ From: cctech <cctech-bounces at classiccmp.org> on behalf of allison <ajp166 at verizon.net> Sent: Wednesday, November 2, 2016 9:30:13 AM To: General Discussion: On-Topic Posts Subject: Re: Looking for Prompt-475 On 11/2/16 10:08 AM, dwight wrote: Yes. I also have both so not an issue. Doesn't hurt that I was an microprocessors and peripherals aps-engineer when both were the drug on the market so I know the difference and how to do either. I'm more interested in 8755A as I have a few tubes of virgin NEC parts. It is. The 8755 is the generic name as they were replaced by the 8755A fairly early in the parts life. Its likely I have to build it as they are scarce and fairly simple. The Intel schematic is helpful in it saves me time I may end of designing it myself.

The UPP had a bug that was never fixed. The level for the reset was inverted for the 4040 from the 4004. They'd used a slow transistor to create the inverter but released the 4040 before the 4001's. The first few fetches would sometimes send it to strange places in the code. The fix was simple, release the 4001 resets before the 4040. The problem was in an app note. Their solution was to put a few NOPs at the start of the code. It worked most of the time. Of course, as an end of life, I don't think it ever got fixed. Dwight ________________________________ From: cctech <cctech-bounces at classiccmp.org> on behalf of allison <ajp166 at verizon.net> Sent: Thursday, November 3, 2016 7:24:35 AM To: General Discussion: On-Topic Posts Subject: Re: Looking for Prompt-475 On 11/2/16 2:18 PM, dwight wrote: I worked for NEC microcomputers.... The other guys. IT was a few lifetimes ago, before DEC. We had a MDS with UPP and a few others in the lad for those times we needed comparative testing. ;) Yes knowing how and doing was sometimes important to know it it even worked! That and some of the micros and such had some very strange things to be done to pump them. Allison

I'd have thought they had it better under control by the 432 time but you never know. Most times on the UPP, you could hit the reset a number of times if there was a problem. The changes in randomness would usually let it reset and start code that would reset. Intel had a number of poorly designed circuits that were on the edge of working. One of the disk controllers with the 3000 series bit slice had a problem if the ROMs used were too fast. I forget which one. They were using the wrong edge of the clock to latch the data. Dwight ________________________________ From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Eric Smith <spacewar at gmail.com> Sent: Thursday, November 3, 2016 5:15:56 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: Looking for Prompt-475 On Thu, Nov 3, 2016 at 8:42 AM, dwight <dkelvey at hotmail.com> wrote: Wow! I noticed the NOPs when I disassembled the code, but had no idea why it was there. The first >NINE< microinstructions in the iAPX 432 GDP Release 1.0 microcode ROM (in the 43201 chip) are all "reset processor", which doesn't affect the micro program counter, but resets much of the other hardware in both the 43201 and 43202 chips. I wonder whether there might have been similar issues.